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Students can Download Economics Chapter 7 Correlation Questions and Answers, Notes Pdf, 1st PUC Economics Question Bank with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Economics Question Bank Chapter 7 Correlation

1st PUC Economics Correlation TextBook Questions and Answers

Question 1.
The unit of correlation coefficient between height in feet and weight in kgs is
Answer:

1. kg / feet
2. percentage
3. non – existent.

Question 2.
The range of simple correlation coefficient is :
Answer:

1. 0 to infinity
2. Minus one to plus one
3. Minus infinity to infinity

Question 3.
If r_xy is positive, the relation between X and Y is of the type.
Answer:

1. When Y increases, X increases
2. When Y deceases, X increase
3. When Y increases, X does not change.

Question 4.
If r =0, the variable X and Y are
Answer:

1. Linearly related
2. Not linearly related
3. Independent

Question 5.
Of the following three measures which can measure any type of relationship:
Answer:

1. Karl Pearsons’s coefficient of correlation
2. Spearman’s rank correlation
3. Scatter diagram

Question 6.
If precisely measured data are available, the simple correlation coefficient is:
Answer:

1. More-accurate than rank correlation coefficient.
2. Less accurate than rank correlation coefficient.
3. As accurate as the rank correlation coefficient.

Question 7.
Why is ‘r’ preferred to co-variance as a measure of association?
Answer:
‘r ’ is Perferred to co-variance as a measure of association because it studies and Measures the direction and intensity of relationship among variables.
It is due to the following reasons:

1. The correlation co – efficient (r) has no unit.
2. The correlation co – efficient is independent of origin as well as a scale

Question 8.
Can ‘r’ lie outside -1 and 1 range depending on the type of data?
Answer:
For any type of data, correlation (r) cannot lie outside the -1 and +1 range. The minimum limit of ‘r’ is -1 and +1 range. The minimum limit of ‘r’ is -1 and the maximum limit of r is +1. As a result, r can never lie outside these two limits. Symbolically.
-1 ≤ r ≥ 1
If in any exercise, ‘r’ is outside this range it indicates error in calculation.

Question 9.
Does correlation imply causation?
Answer:
No, zero correlation does not imply causation. It implies co-variation. It should never be interpreted as implying causes and effect relation. Correlation studies and measures the direction and intensity of relationship among variable.

Question 10.
When is rank correlation more precise than simple correlation coefficient?
Answer:
Rank correlation is more precise than simple correlation when the variables cannot be measured meaningfully as in the case of prices, income, weight etc. Ranking may be more meaningful when the measurement of the variables are suspect. Ranking may be a better alternative to quantification of qualities.

Question 11.
Does zero correlation does not mean independence?
Answer:
No, zero correlation does not mean independence. If there is zero correlation, it means the two variables are not correlated and there is no linear relation between them. However, other types of relation may be there and they may be not independent.

Question 12.
Can simple correlation co – efficient measure any type of relationship?
Answer:
Simple correlation co-efficient cannot measure any type of relationship. It measures any type of relationship only between two variables. If the variables are more than two or we want to measure the correlation between the productivity of wheat, temperature, and quantity of rain, then simple correlation cannot measure this type of relationship. This type of relationship can be measured with the help of partial or multiple correlation co – efficient.

Question 13.
Collect the prices of five vegetables from your local market everyday for a week. Calculate their correlation co – efficient. Interprt the result. Name of vegetables and their prices (in Rs.)
Answer:

r = 1 – \(\frac{6 \sum D^{2}}{N^{3}-N}\)

i. Correlation between potato and cabbage:
r = 1 – \(\frac{6 \times 51}{(343-7)}\) = 1 – \(\frac{306}{306}\) = 1 – 0.911 = 0.089

ii. Correlation between cabbage and tomato:
r = 1 – \(\frac{6 \times 36}{343-7}\) = 1 – \(\frac{216}{336}\) = 1 – 0.64 = 0.36

iii. Correlation between tomato and peas:
r = 1 – \(\frac{6 \times 37}{343-7}\) = 1 – \(\frac{222}{336}\) = 1 – 0.66 = 0.34

iv. Correlation between peas and carrot:
r = 1 – \(\frac{6 \times 29}{343-7}\) = 1 – \(\frac{174}{336}\) = 1 – 0.52 = 0.48

v. Correlation between peas and carrot:
r = 1 – \(\frac{6 \times 37}{343-7}\) = 1 – \(\frac{222}{336}\) = 1 – 0.66 = 0.34

vi. Correlation between carrot and potato:
r = 1 – \(\frac{6 \times 49}{343-7}\) = 1 – \(\frac{294}{336}\) = 1 – 0.875 = 0.13

Interpretation of Result:
It is clear from the above result that every vegetable is corre-lated. There is a positive correlation among these vegetables. Co-relation of peas and carrot is 0.48 which is highest and correlation of potato and cabbage is 0.089 which is lowest.

Question 14.
Measure the height of your classmates. Ask them the height of their benchmate. Calculate the correlation coefficient of these two variables. Interpret the result.

Answer:

r = 0.688 Ans
It is clear from the above analysis that there is a positive correlation between the asked height and measured height of the classmates.

Question 15.
Measure the hieght of your classmates. Ask them the height of their benchmate. Calculate the correlation coefficient of these two variables. Interpret the resuit.
Answer:
Impartiality, secularism, beauty, honesty, patriotism etc are some variables where accurate measurement is difficult.

Question 16.
Interpret the values of r as 1, -1, and 0.
Answer:

1. r as 1 means that there is perfect positive relationship between two variables.
2. r as -1 means that there is perfect negative relationship between two variables.
3. r as 0 means that there is lack of correlation between two variables.

Question 17.
Why does rank correlation co-efficient differ from Pearsonian correlation coefficient?
Answer:
Rank correlation co-efficient is more often used to measure the linear relationship between the qualitative variable whereas Karl Pearsn’s method of correlation co – efficient measures the linear relationship between the quantitative variables.

Question 18.
Calculate the correlation co – efficient between the heights of fathers in inches (X) and their sons (Y)

Answer:

Question 19.
Calculate the correlation co-efficient between X and Y and comment on their relationship.

Answer:


Hence, r 0
Two values X and Y are un – correlated.
There is no linear correlation between them.

Question 20.
Calculate the correlation co-efficient between X and Y and comment on their relationship.

Answer:

1st PUC Economics Correlation Additional Questions and Answers

1st PUC Economics Correlation Very Short Answer Type Questions

Question 1.
Define Correlation?
Answer:
According to the Croxton and Cowden correlation is defined as “when the relationship is of a quantitative nature the appropriate statistical tool for discovering and measuring the relationship and expressing it in a brief formula is shown as correlation’’.

Question 2.
What are the principal methods of calculating coefficient of correlation?
Answer:
The principal methods are as under:

1. Scattered Diagram method
2. Carl Pearson’s coefficient or correlation
3. Spearman’s Rank correlation coefficient

Question 3.
What is the difference between positive and negative correlation?
Answer:
When two variables move in same direction such a relation is called positive correlation for example relationship between price and supply when two variable change in different direction it is called negative correlation for example relationship between price and demand.

Question 4.
State the kinds of correlation?
Answer:

1. Positive and negative correlation
2. Linear and non-linear correlation
3. Simple and multiple correlation.

Question 5.
Coefficient of correlation is between -1 and +1. How would you express it arithmetically?
Answer:
-1 < r < +1

Question 6.
What is the nature of correlation of variables when they move in the same direction?
Answer:
Positive correlation.

Question 7.
What is the principal shortcoming of scattered diagram as a method of estimates correlation.
Answer:
A Scattered diagram does not measure the precise extent of correlation it give only an approximate idea of the relationship, it is not a quantitative measure of the relationship.

Question 8.
When is rank correlation method used?
Answer:
Rank correlation method is used for the variable whose quantitative measurement is not possible such as beauty, bravery or wisdom.

Question 9.
What does correlation measure?
Answer:
Correlation measures the direction and intensity of relationship it measures covariation and not causation.

Question 10.
What does the presence of correlation between two variables X and Y simply mean?
Answer:
The presence of correlation between variables X and Y simply means that when value of one variables is found to change in one direction the value of other variables is  found to change either in the same direction or in the opposite direction but indefinite way.

Question 11.
Can ‘r’ lie outside -1 and +1 range depending on the type of data?
Answer:
No. ‘r ’ cannot lie outside -1 and +1 range depending on the types of data, it lies between minus one and plus one symbolically -1 if in any excercise ‘r ’ is outside this range it indicates error in calculation.

Question 12.
Does correlation imply causation?
Answer:
No correlation does not imply causation it implies covariation it should never be interpreted as implying causes and effect relation.

Question 13.
When is Rank Correlation more precise than simple correlation coefficient?
Answer:
Rank Correlation is more precise than simple correlation when the variable cannot be measured meaningfully as in the case of price income weight etc ranking may be move meaningful when the measurement of the variable are suspect ranking may be a better alternative to quantification qualities.

Question 14.
When is Rank correlation preffered to Person’s co-efficient?
Answer:
Rank correlation is preffered to Person’s coefficient when extreme values are present.

Question 15.
What is the relationship between r and in general?
Answer:
In general  \({ r }_{ \swarrow }\)≤ r

Question 16.
What is the limitation of spearman rank correlation?
Answer:
Spearman’s rank correlation is not as accurate as the ordinary method this is due to fact that all the information concerning the data is not utilised.

Question 17.
When do r and r_k give identical results?
Answer:
v and v_k give identical results when the first difference of the values of the items in the series of arranged in the order or magnitude are constant.

Question 18.
In which situation is the use of rank correlation method suitable?
Answer:
The use of rank correlation is suitable when data cannot be directly quantitatively measured.

Question 19.
Which type of correlation is indicated by the values of X and Y variables.

Answer:
Here r = + 1 as values of X and variables move in the same direction.

Question 20.
Under what situation is r = -1.
Answer:
r = -1 when the values of two variables X and Y move in the opposite directions.

Question 21.
When is the correlation called linear?
Answer:
When the change ratio in values of the two variables is constant.

Question 22.
If a change in a variable does not bring about change in the other variable in the same relation there will be what kind of correlation between them.
Answer:
Non-linear correlation.

Question 23.
Where does correlation between two variables concentrate?
Answer:
Correlation between two variables concentrate between + 1 and – 1.

Question 24.
What do you mean by absence of correlation?
Answer:
By absence of correlation we mean that there is no relationship between the values of series, in this case, r = 0.

Question 25.
Which type of correlation is indicated by the following scatter diagram?
Answer:
The scattered diagram given in the question indicate the positive relation.

Question 26.
Which type of correlation between two variables is indicated by a scatter line sloping downward to right?
Answer:
Negative relation between two variables.

Question 27.
Which type of correlation is indicated by the values of X and Y variables?

Answer:
Here r = – 1 because the value of x and y variables move in the opposite direction.

Question 28.
What does a high value of ‘r’ indicate?
Answer:
A high value of ‘r ’ indicates linear relationship. If value is said to be high when it is close to +1 or -1.

Question 29.
Give anyone property of correlation coefficient? (r)
Answer:
The value of ‘r’ is unaffected by the change of origin and change of scale.

Question 30.
What does a low value of ‘r’ indicate?
Answer:
A low value of ‘r ’ indicates a weak linear relation its value is said to be low when it is close to zero.

Question 31.
Give the formula of ranking coefficient of correlation of spearman.
Answer:
\(\mathrm{V}_{\mathrm{k}}=1-\frac{6 \sum \mathrm{D}^{2}}{\mathrm{n}\left(\mathrm{n}^{2}-\mathrm{n}\right)}\)

Question 32.
If the points in a scatter diagram tend to cluster about a straight line which makes an angle of 30 with the X axis what would you say about the strength of association between X and Y?
Answer:
It shows less than proportionate change of there exists a low degree of association between X and Y.

Question 33.
Correlation remains always between -1 and +1 how is it expressed in mathematical language?
Answer:
-1 ≤ r ≤ + 1

Question 34.
Why is ‘r’ preferred to co-variance as a measure of association?
Answer:
‘r ’ is preffered to co-variance as a measure of association because it studies and mean some the direction and intensity of relationship among variables.

Question 35.
Does zero correlation mean independence?
Answer:
No, but there is possibility o independence.

Question 36.
Can simple correlation co-efficient measure any type of relationship?
Answer:
No.

Question 37.
Collect the price of five vegetable from your local market every day for a week. Calculate their correlation co – efficient interpret the result?
Answer:
Students are supposed of collect the price of any five vegetables from the market over a week. Then they should calculate their correlation of co – efficients.

Question 38.
List some Variables, Where accurate measure is difficult?
Answer:
Impartiality is secular is unbeauty, honesty, Patritism etc -are some variable where accurate measurement is difficult.

Question 39.
Interpret the values of V as 1,-1 and 0.
Answer:

1. r as 1 means that it is perfect positive relationship between two variables.
2. r as -1 means that there is perfect negative relationship between two variables.
3. r as O means that there is Lack of correlation between two variables.

Question 40.
Why does rank correlation co – efficient differ from Pearsonian correlation co-efficient.
Answer:
Because rank correlation co-efficient provider & measure of time association between ranks to these limits and not their values.

1st PUC Economics Correlation Short Answer Type Questions

Question 1.
Give the definition of correlation give the meaning of following. r = 0, r = +1, r = -1.
Answer:
According to Croxton and Cowden, ‘when the relationship is of a quantitative nature the appropriate statistical tool for discovering and the measuring the relationship and expressing it in a brief formula is known as statistics.

1. When r = 0, It implies that there exists no relationship between two variables X and Y in other ways r = 0 shows the absence of relationship.
2. r = 1, Shows that there is perfect correlation between two variables X and Y.
3. r = -1, Shows that there is perfect negative relationship between two variables X and Y.

Question 2.
Give the value of correlation under following position.

1. Perfect correlation and negative
2. Perfect correlation and positive
3. No correlation.

Answer:

1. When correlation is perfect and negative than the value of r = -1.
2. When correlation is perfect and positive than the value of r = +1
3. When there is no correlation then the value of r = 0.

Question 3.
Define positive and negative correlation with examples?
Answer:
1. Positive correlation:
When two variables move in the same direction that is when one increases the other also increases and when one decreases the other also decreases, such a relationship is called positive correlation for example the relation between price and supply.
Increase in the value of both variables:

2. Negative correlation:
When two variables change in different direction, it is called negative correlation for example relationship between price and demand when prices rise other things remaining constant, demand falls and when price falls demand rises.

Question 4.
What is perfect correlation give two examples?
Answer:
Perfect correlation is that when changes in two related variables are exactly proportional It is of two types.

1. Positive perfect correlation and
2. Negative perfect correlation

There is perfect positive correlation between the two variables if equal proportional changes are the same direction. It is expressed as +1. If equal proportional changes are in the reverse direction then there is negative perfect correlation and it is described as -1.

a. Example of positive perfect correlation

b. Example of perfect negative correlation

Question 5.
Define simple and Partial correlation.
Answer:
1. Simple correlation:
When the relationship between two variables is studied and if these are is dependent then such correlation is called simple correlation. For example relationship between income and expenditure.

2. Partial correlation:
When more than two variables are involved and out of these the relationship between two variables is studied only treating other variables as constant, then such correlation is partial.

1st PUC Economics Correlation Long Answer Type Questions

Question 1.
Calculate r with the help of following data.

Answer:
Calculation of r between schooling of farmers and annual yields.

Question 2.
What steps are involved in the procedure calculating Karl Pearson’s coefficient of correlation by the direct method?
Answer:
Steps involved in the procedure of calculation of Karl Pearson’s coefficient by direct method.

1. Calculate mean value X and Y
2. Calculate deviations of values of X series from mean value
3. Square the deviations.
4. Calculate deviation of values of Y series from mean value
5. Square the deviation
6. Multiply the square of deviation of X series with the square of deviations of Y series

Use the following formula for calculating correlation coefficient

\(\mathrm{r}=\frac{\sum \mathrm{XY}}{\sqrt{\mathrm{x}^{2}} \sqrt{\mathrm{y}^{2}}}\)
\(\mathrm{r}=\frac{\sum \mathrm{XY}}{\sigma \mathrm{x} \times \sigma \mathrm{y}}\)

σ x = S. D of X series
σ y = S. D of Y series

Question 3.
Calculate the height and weight of the student of a class.

Answer:

Question 4.
Calculate Karl Pearson’s co-efficient of correlation the help of following data?

Answer:
Calculation of Pearson’s co – efficient of correlation X Series \(\overline{\mathrm{x}}\) = 18, Y series
\(\bar{y}=\) = 19.

Question 5.
Calculation of Karl Peasson’s correlation co – efficient.

Answer:

= \(\frac{1720}{1790.81}\) = 0.96

Question 6.
Calculate Karl Peasson’s co-efficient from the following data

Answer:
Calculation of Karl Peasson’s correlation co – efficient.

Question 7.
Calculate correlation between the two variables.

Answer:

Question 8.
Calculate the co-efficient of raqnic correlation from the following data:

Answer:

Students can Download 1st PUC Chemistry Model Question Paper 4 with Answers, Karnataka 1st PUC Chemistry Model Question Papers with Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.

Karnataka 1st PUC Chemistry Model Question Paper 4 with Answers

Time: 3.15 Hours
Max Marks: 70

Instruction:

1. The questions paper has five parts A, B, C, D and E. All parts are compulsory.
2. Write balanced chemical equations and draw labeled diagram wherever allowed.
3. Use log tables and simple calculations f necessary (use of scientific calculations is not allowed).

Part – A

I. Answer ALL of the following (each question carries one mark): ( 10 × 1 = 10 )

Question 1.
Give an example for a homogeneous mixture.
Answer:
Air, Gasoline, Sea water, etc.

Question 2.
Write the ideal gas equation for ‘n’ moles of a gas.
Answer:

Question 3.
What is hydronium ion?
Answer:
H₃O⁺ is called hydronium ion

Question 4.
Write the IUPAC name of an element with atomic number 107.
Answer:
Ununnillium.

Question 5.
Identify the element in the compound K₂Cr₂O₇ showing negative oxidation number.
Answer:
Oxygen.

Question 6.
Name the gas liberated when a piece of sodium metal is added into the water.
Answer:
Hydrogen (H₂).

Question 7.
What is Zeolite?
Answer:
Zeolites are alumino silicates having a three-dimensional cage like structure with a general
formula Mⁿ⁺_x/n [(AlO₂)_x(SiO₂)_y]H₂O, where M is a cation ion like K⁺Na⁺,Ca²⁺.
These are obtained by replacing some of the silicon atoms by aluminium atoms. The aluminosilicate thus formed acquires negative charge and it is balanced by the cations like
Na⁺,K⁺ or Ca²⁺

Question 8.
Give the composition of water gas.
Answer:
Water gas [CO + H₂] is a mixture of carbon monoxide and hydrogen.

Question 9.
Write the bond line formula for 3-chloro octane.
Answer:

Question 10.
Alkanes are not soluble in water. Give reason.
Answer:
Non-polar and saturated.

Part – B

II. Answer any FIVE of the following questions carrying TWO marks: (5 x 2 = 10 )

Question 11.
Calculate the molarity of NaOH in the solution, prepared by dissolving lOg in enough water to form 500mL of the solution. Molar mass of NaOH is 40 g mol^-1
Answer:

Question 12.
Give any two differences between ideal and non-ideal (real) gas.
Answer:
Ideal Gas

1. Obeys ideal gas equation PV = nRT.
2. Ideal gas does not exist in nature.

Real Gas:

1. Does not obeys the ideal gas equation but obeys van der Waals equation.
2. All gases which exist in nature are real gases.

Question 13.
Mention any two conditions for the combination of atomic orbitals.
Answer:
The conditions for the combination of atomic orbitals are:
(a) The combining atomic orbitals should have comparable energy.
1s orbital can combine with another Is orbital but not with 2s orbital.

(b) The combining atomic orbitals should have the same symmetry about the molecular axis. For example: 2p orbital can combine with 2s orbital or another 2p_z orbital but not with 2p_x or 2p_y.
2s cannot combine with 2p_x or 2p_y .
(c) The combining atomic orbitals must overlap to the maximum extent.

Question 14.
Complete the following equations:
(i) 4Li + O₂ → _____
Answer:

(ii) 2Na + O₂ → _____
Answer:
2Na + O₂ → Na₂O₂ (Sodium peroxide)

Question 15.
(a) What is dry ice?
Answer:
Solid CO₂ is called dry ice. It is called dry ice because it directly changes into gaseous state without becoming liquid.

(b) Write the formula of basic structural unit of silicates.
Answer:
Silicates are the compounds in which the anions are present as either discrete SiO^- tetrahedral or a number of such units joined together through comers.

Silicates are basically made up SiO⁴_4- tetrahedra (as shown in the figure) in which silicon atom is bonded to four oxygen atoms in a tetrahedral manner. In the figure, big circles indicate oxygen atoms and small circle indicates silicon atoms.

Question 16.
Explain Wurtz reaction with a suitable example.
Answer:
When alkyl halides are heated with sodium metal in ether medium higher alkanes are formed. This reaction is known as Wurtz reaction and employed for the synthesis of higher alkanes containing even number of carbon atoms.

Question 17.
What are benzenoids? Give an example.
Answer:
Aromatic compounds with palanar structure and delocalized n e A above and below the plane of the ring, eg: Benzene, Toluene.

Question 18.
How ozone is formed in the atmosphere? Give equations.
Answer:
The UV radiations of very short wavelength (< 250 nm) have sufficient energy to cause photo – dissociation of oxygen molecules into oxygen atoms. Highly reactive oxygen atoms combine with oxygen molecules to form ozon

Part – C

III. Answer any FIVE of the following questions carrying THREE marks: (5 x 3 = 15 )

Question 19.
(a) Write the general electronic configuration of p-block elements.
Answer:
General electronic configuration of p-block elements is ns² np^1_6.
Both s and p block together is called representative or normal elements.

(b) How does ionisation enthalpy varies along a period and down the group?
Answer:
The amount of energy required to remove the most loosely bound electron from an isolated gaseous atom. Ionization energy increases along the period and decreases down the group.

Question 20.
Define the terms (a) Bond angle (b) Bond order (c) Co-valent radius.
Answer:
(a) Bond angle: It is defined as the “angle between the oribitals containing bonding electron pairs around the central atom in a molecule or in a complex ion”. It is expressed in degrees.
Example: In CO₂ the bond angle is 180°. So CO₂ has linear shape.
(b) Bond order: It is the number of covalent bonds holding the atoms in the molecule. Example: If the bond is formed by the sharing of two electron pairs, then the bond order is 2. O = O or C = C bond in alkenes.
(c) Co-valent radius: A chemical bond formed by the sharing up of one or more electrons between the atoms.

Question 21.
Give any three important postulates of VSEPR theory.
Answer:
Bonding : The bond formation takes place if there exists impaired electron in the valance shell.
Shape : The geometry or the shape of a molecule depends on the number of valence shell electrons surroundings the central atom.
Repulsion : Electron pair tend to repell one another because electron clouds have similar charge.
Stability : As a result of electron pair repulsion these electron pairs try to stay apart as possible in order to attain minimum energy and maximum stability.
Repulsive interaction : Lane pair with lane pair electrons are having maximum repulsive interaction, bond pair-bond pair electrons are having minimum repulsive interaction. When angle of repulsion decreases angle between the electron pair increases (109°. 28′ less repulsion, 104° more repulsion).

Question 22.
Explain bonding in H₂ molecule based on the basis of Molecular orbital theory.
Answer:
Atomic number of hydrogen is 1 = Is’

(a) Electronic configuration of hydrogen molecule is σ1s²σ*1s⁰
(b) Bond order – \(\frac{2-0}{2}\) = 1
(c) Magnet property = diamagnetic.

Question 23.
(a) What is the oxidation number of Cl in KClO,sub>3 ?
Answer:
+5

(b) Write the separate equations for the oxidation and reduction reactions occuring in the given redox reaction. 2Fe + HCI → FeCL₂ + H₂
Answer:

Question 24.
Explain the process of softening of temporary hardness by Clark’s method.
Answer:
Clark’s process: Temporary hardness can be removed by the addition of a calculated amount of lime, where magnesium carbonate or calcium carbonate is precipitated.
Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃ +2H₂O
Mg(HCO₃)₂ + Ca(OH)₂ → CaCO₃ + MgCO₃ + 2H₃O

Question 25.
(a) Give the composition of plaster of paris and mention one use of it.
Answer:
Plaster of Paris is CaSO₄ + \(\frac{1}{2}\)H₂O It is prepared by heating gypsum at 373 K.

Uses:
(i) It is used for manufacture of statues,
(ii) It is used for filling gaps before white washing.

(b) Write any one biological importance of Magnesium.
Answer:
Biological importance of Mg and Ca are:
(a) Mg ion is present in chlorophyll which is responsible for photosynthesis.
(b) Ca²⁺ ions are required for maintaining heart beat.
(c) Ca²⁺ and Mg²⁺ ions are required for clotting of blood.

Question 26.
(a) Boron shows anamolous behaviour with other elements of the same group. Give reasons.
Answer:

1. Due to smaller size
2. High ionisation enthalpy
3. High electronegativity.

(b) Name the gas liberated when formic acid is heated with concentrated H₂SO₄.
Answer:
Pure carbon monoxide is formed by the dehydration of formic acid with cone. H₂SO₄.

Part – D

IV. Answer any FIVE of the following questions carrying FIVE marks: ( 5 x 5 = 25 )

Question 27.
(a) The percentage composition of an organic compound found to contain 39.9% carbon, 6.7% hydrogen and the rest is oxygen. If the molecular mass of the compound is 60 gmol^-1. Determine the molecular formula of the compound.
Answer:
Percentage of oxygen = 100 – (39.9 + 6.7) = 100 – 46.6 = 53.4

∴ Empirical formula = CH₂O
Molecular mass = Eq. mass x basicity = 60 x 1 = 60
Empirical formula weight = CH₂O = 12 + 2 + 16 = 30
Nows 30n = 60 => n = 2
∴ Molecular formula = (Empirical formula) x n = (CH₂O)₂ = C₂H₄O₂

(b) State Avagadro law.
Answer:
Avogadro’s law states that “Equal volumes of all gas under similar conditions of temperature and pressure contain equal number of mole cols.”

Question 28.
(a) Give any three postulates of Bohr’s theory of atomic model.
Answer:
Bohr’s model of an atom, the postulates are:

1. Electrons revolve around the nucleus of an atom in a certain definite path called orbit or stationary state of shell.
2. The shells are having different energy levels denoted as K, L, M, N…
3. As long as the electron remains in an orbit, they neither absorb nor emit energy.
4. The electron can move only in that orbit in which angular momentum is quantized,
   i.e., the angular momentum of the electron is an integral multiple of \(\frac{\mathrm{h}}{2 \pi}\)

(b) State Hund’s rule of maximum multiplicity.
Answer:
Hund’s rule or maximum multiplicity: Electron pairing does not take place until orbitals of same energy are singly occupied.

Question 29.
(a) Name the four quantum numbers and mention what they indicate?
Answer:
In order to define state energy and location of electron a set of four numbers are used. These numbers are called quantum numbers, (i) Principal quantum number (n). (ii) Azimuthal quantum number (1). (iii) Magnetic quantum number (m). (iv) Spin quantum number (s).

(b) What is node?
Answer:
The region where probability of finding the electron is zero is called a node.

Question 30.
(a) Write the important postulates of Kinetic theory of gases.
Answer:

1. Gases are made up of large number of the minute particles.
2. Pressure is exerted by a gas.
3. There is no loss of kinetic theory.
4. Molecules of gas attract on one another.
5. Kinetic energy of the molecule is directly proportional to absolute temperature.
6. Actual volume of the gaseous molecule is very small.
7. Gaseous molecules are always in motion.
8. There is more influence of gravity in the movement of gaseous molecule.

(b) What is Boyle’s temperature?
Answer:
The temperature at which real gases obey ideal behaviour for appreciable range of pressure is called Boyle’s temperature (or) Boyle’s point.

(c) Falling liquid droplets are spherical. Give reason.
Answer:
Due to surface tension.

Question 31.
(a) Calculate the standard enthalpy of formation of benzene from the following data.
Answer:
C₆H₆ + O₂ + \(\frac{15}{2}\)O₂  → 6CO₂ + 3H₂O_(l); ∆H= – 3264KJ
C_(s) + O_2(g)  → CO_2(g); ∆H = -393.5KJ
H₂ + \(\frac{1}{2}\)O₂ → H₂O_(l); ∆H = -285.9KJ

(b) What is entropy?
Answer:
Measure of disordemess of a system.

Question 32.
(a) Calculate the total work done when one mole of a gas expands isothermally and reversibly from an intial volume of 10dm³ to a final volume of 20dm³ at 298K.
Answer:
T = 27°C = 27 + 273 = 300K , V₁ = 10 dm³ V₂ = 20 dm³ , R = 8.314 J/K/mol
w = -2.303 nRTlog \(\left(\frac{v_{2}}{v_{1}}\right)\)
w = -2.303 x 1 x 8.314 x 300 x log \(\left(\frac{20}{10}\right)\)= -2.303 x 8.314 x 300 x log2
= -2.303×8.314x300x0.3010 = -1729 joule = -1.723 kJ.

(b) What is an intensive property? Give an example.
Answer:
Intensive property of a system is that property of the system which does not depend on the quantity of the substance present in the system. E.g; Density, Viscosity.

Question 33.
(a) For the hydrolysis of sucrose the equilibrium constant K_c is x x 10^-3 at 300K calculate ∆G° at 300K?
Answer:
Given K_c = 2 x 10^-3
T = 300K; ∆G° = ?
We know that ∆G° = -2.303 RT log K_c = -2.303 x 8.314 x 300 x 2 x 10^-3
= -2.303 x 8.314 x 3 x 2 = -11.488 J/mol.

(b) Explain common ion effect with suitable example.
Answer:
Suppression in the degree of dissociation of a weak electrolyte by the addition of a common ion is called common ion effect.

Question 34.
(a) Calculate the pOH of a solution obtained when 0.05 mol NH₄Cl is added and dissolved , in 0.025M ammonia solution. (Given Kb for ammonia = 1.77 x 10^-5).
Answer:
pK_b = -logK_b = -logl.8 x 10^-5 = -(5.2553) = 4.7447
p^OH = pK_b + log \(\frac{[\text { salt }]}{[\text { base }]}\) = 4.7447 + log \(\frac{0.05}{0.12}\) = 4.74 – 0.38 = 4.36
∴ pH = 14 – p^OH= 14 – 4.36 = 9.64

(b) What is solubility product?
Answer:
It is the product of the molar concentration of ions of the saturated solution of a sparingly soluble solution of the salt and the coefficients are raised to their powers at constant temperature.

Part – E

V. Answer any TWO of the following questions carrying FIVE marks: ( 2 x 5 = 10 )

Question 35.
(a) Write the principles involved in the estimation of
(i) Halogens (ii) Sulphur present in an organic compound by Carius method.
Answer:
(i) Halogens: When an organic compound containing halogen (Cl, Br or 1) is heated in a sealed tube with fuming nitric acid and excess of silver chloride, silver halide is formed from the mass of silver halide obtained, the percentage of the halogen can be calculated.

Procedure: In a hard glass tube (Carius tube), 5 ml of fuming HNO₃ and 2 to 2.5 g AgNO₃ are taken. A small narrow weighing tube, containing a small amount (nearly 0.15 -0.2g) of accurately weighed organic compound, is introduced in the Carius tube in such a way that nitric acid does not enter the weighing tube. The Carius tube is now sealed and heated in a furnace at 300°C for about six hours.

The tube is then cooled and its narrow end is cut off and the contents are completely transferred to a beaker by washing with water. The precipitate of silver halide formed is filtered through a weighed sintered glass crucible. It is washed, dried and weighed.

Observation and calculation:
(i) Mass of organic compound taken = W₁g
(ii) Mass of silver halide obtained = w₂g
(a) For chlorine:

143.5g of AgCl contains 35.5 g of chlorine.
w₂g of AgCl will contain \(\frac{35 \cdot 5 \times w_{2}}{143 \cdot 5}\) of chlorine
∴ % Cl₂ = \(\frac{35 \cdot 5 \times w_{2}}{143 \cdot 5} \times \frac{100}{w_{1}}\)

(b) For bromine:

188 g of AgBr contains 80 g of bromine
w₂ of AgBr will contain \(\frac{980 \times w_{2}}{188}\) g of bromine

(ii) Sulphur Present in an organic compound by carius method:
Principle: An organic compound containing sulphur to heated in Carius tube with fuming nitric acid or sodium peroxide. Sulphur present is oxidised to sulphuric acid. It is then precipitated as burium sulphate by adding excess of barium chloride solution. The precipitate formed is filtred, washed, dried and weighed. The % of S is calculated from the mass of barium sulphate.

Calculations: Mass of organic substance = ‘m’
Mass of barium sulphate formed = ‘x’ g.
Molecular mass of barium sulphate = 233 g.

(b) Name the element estimated by Kjeldahl’s method.
Answer:
Nitrogen.

Question 36.
(a) Describe the estimation of Carbon and Hydrogen by Liebig’s method.
Answer:

Principle: A known mass of an organic compound is strongly heated with dry cupric oxide (CuO), when carbon and hydrogen are quantitatively oxidized to CO₂ and H₂O respectively. The masses of CO₂ and H₂O thus formed are determined. From this, the percentages of carbon and hydrogen can be calculated.
Procedure : Pure and dry oxygen is passed through the entire assembly of the apparatus (Figure) till the CO₂ and moisture is completely removed.

A boat containing weighed organic substances is introduced inside from one end of the combustion tube by opening it for a while. The tube is now strongly heated till the whole of the organic compound is burnt up. The flow of oxygen is continued to drive CO₂ and water vapours completely to the U-tubes. The apparatus is cooled and the U-tubes are weighed separately.

Observation and calculations:

1. Mass of organic compound taken = w.g.
2. Mass of water produced = x g (Increase in mass of CaCl₂ tube).
3. Mass of carbon dioxide produced = y g (Increase in mass of KOH tube).

To determine % of carbon:
Molar mass of CO₂ = 44g mol^-1
Now, 44g of CO₂ = contains 12 g of C
y g of CO₂ will contain of \(\frac{12 y}{44}\) f of C
This amount of carbon was present in w. g. of the substance
∴ % C = \(\frac{12 y}{44} \times \frac{100}{w}\)

To determine % of Hydrogen
Molar mass of water = 18 g mol^-1
Now, 18 g of H₂O contains 2 g of H₂O
∴ x g of H₂O will contain \(\frac{2 x}{18}\) g of H₂O
This amount of hydrogen was present in weight of substance.
∴ H₂ = \(\frac{2 x}{18} \times \frac{100}{w}\)

(b) What is Cracking?
Answer:
The decomposition of higher alkane into a mixture of lower alkanes alkenes, etc. by the application

Question 37.
(a) Explain the mechanism of chlorination of Methane.
Answer:
Mechanism of chlorination of methane involves three types:

Step 1: Initiation: Chlorine absorbs energy and undergoes homolysis to give chlorine free radicals.

Step 2: Propagation: Chlorine free radical reacts with methane to give methyl free radical.

The methyl free radical reacts with chlorine to form methyl chloride and chlorine free radical.

Step 3: Termination: Free radials combine to form stable products.

(b) Name the product formed when phenol vapours are passed over heated zinc dust. Write the chemical equation.
Answer:
Benzene