Question Set C

CBSE 12th Standard Chemistry Electrochemistry HOT Questions Study Material - QB365

Download CBSE Class 12th Standard CBSE Chemistry question papers, sample papers, important questions, and previous year solved papers in PDF format. Get free study materials, NCERT solutions, and exam preparation resources for Class 12th Standard CBSE Chemistry

Questions:

Generic 2

6 x 2 = 12

The K_H value for H₂in water is 71.18 k bar but its value changes to 3. 67 k bar when the solvent is benzene. Why?

How does a change in temperature affect the rate of a reaction? How can this effect on the rate constant of a reaction be represented quantitatively?

Express the relation among conductivity of the solution in the cell, the cell constant and resistance of solution in the cell.

What are the units of the rate constant of a pseudo unimolecular reaction ?

What concentration of nitrogen should be present in a glass of water at room temperature?Assume temperature of 25⁰C, a total pressure of 1 atmosphere and mole fraction of nitrogen in air as 0.78 [K_H for nitrogen = 8.42\(\times\)10^-7 M/mm Hg].

The molar conductivity of 1.5 M solution of an electrolyte is found to be 138.9 S cm² mol^-1 . Calculete the conductivity of this solution.

Multiple Choice Question

15 x 1 = 15

Solubility of gases in liquids decreases with rise in temperature because dissolution is an

(a)

endothermic and reversible process

(b)

exothermic and reversible process

(c)

endothermic and irreversible process

(d)

exothermic and irreversible process

The slope in the plot of In[R]vs time for a first order reaction is

(a)

+k/2.303

(b)

-k

(c)

-k/2.303

(d)

The equilibrium constant of the following reaction at 298 K is 1 x 10⁸ for
2Fe³⁺(aq) + 2I^-(aq) \(\rightleftharpoons\) 2Fe²⁺(aq) + I₂
\(\mathrm{E}_{\mathrm{I}_{2} \mid \mathrm{I}^{-}}^{\circ}=+0.54 \mathrm{~V} \quad \mathrm{E}_{\mathrm{Fe}^{3+} \mid \mathrm{Fe}}^{\circ}=?\)

(a)

+ 1.006 V

(b)

+ 0.77 V

(c)

- 0.77 V

(d)

- 0.625 V

10.

The true statement about mercury cell is

(a)

it is used in high current devices

(b)

here Zn - Hg acts as cathode and a paste of C+ HgO as anode.

(c)

the cell potential remains constant due to non-involvement of such a ion, concentration of which can change during its whole life.

(d)

All of the above

11.

Same amount of electricity is passed through the solutions of HCI and CuSO₄. If 6.35g of copper is deposited from CuSO₄ solution, the amount of hydrogen liberated at STP will be

(a)

0.01

(b)

0.1

(c)

0.001

(d)

12.

1.5A current is flowing through a metallic wire. If it flows for 3 hrs, how many electrons would flow through the wire?

(a)

2.05x10²²electrons

(b)

1.0 x10²³ electrons

(c)

10²⁴electrons

(d)

4.5x10²³ electrons

13.

t_1/4 can be taken as the time taken for the concentration of a reactant to drop to \(\frac {3}{4}\) of its initial value. If the rate constant for a first order reaction is K, then t_1/4 can be written as

(a)

0.10/K

(b)

0.29/K

(c)

0.69/K

(d)

0.75/K

14.

At 500 K, the half-life period of a gaseous reaction at the initial pressure of 80 kPa is 350 sec. When the pressure is 40 kPa, the half-life period is 175 sec. The order of reaction is

(a)

second

(b)

more than zero but less than first

(c)

zero

(d)

first

15.

For the reaction A + 2 B \(\longrightarrow\) C, the reaction rate is doubled if the increased by four times when concentration of both A and B are increased by four times. The order of reaction is

(a)

(b)

(c)

(d)

16.

The time for half period of a certain reaction A \(\longrightarrow\) Products is 1 hour. When the initial concentration of the reactant 'A' is 2.0 mol L^-1, how much 0.50 to 0.25 mol L^-1 it is a zero order reaction ?

(a)

0.25 h

(b)

1 h

(c)

4 h

(d)

0.5 h

17.

The van't Hoff factor for 0.1 M Ba(NO₃)₂ solution is 2.74. The degree of dissociation is

(a)

91.3%

(b)

87%

(c)

100%

(d)

74%

18.

Solution A contains 7 g/L MgCI₂ and solution B contains 7 g/L of NaCI. At room temperature, the osmotic pressure of

(a)

solution A is greater than B

(b)

both have same osmotic pressure

(c)

solutin B is greater than A

(d)

can't determine.

19.

K_f for water is 1.86 K kg mol^-1 . If your automobile radiator holds 1.0 kg of water, how many grams of ethylene glycol (C₂H₆O₂) must you add to get the freezing point of the solution lowered to - 2.8^oC ?

(a)

27 g

(b)

72 g

(c)

93 g

(d)

39 g

20.

The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called -------------

(a)

Cell potential

(b)

Cell emf

(c)

Potential difference

(d)

Cell voltage

21.

5ml of 1 N HCI, 20ml of N/2 H₂SO₄ and 30ml of N/3 HNO₃ are mixed together and the volume made to one litre. The normality of the resulting solution is

(a)

N/5

(b)

N/10

(c)

N/20

(d)

N/40

Generic 3

6 x 3 = 18

22.

At what partial pressure, oxygen will have a solubility of 0.05 g L^-1 in water at 293 K? [Henry's constant (K_H) for O₂ in water at 293 K is 34.86 k bar. Assume the density of the solution to be same as that of the solvent.]

23.

A 5 percent solution (by mass) of cane-sugar (M.W. 342) is isotonic with 0.877% solution of substance X. Find the molecular weight of X.

24.

The rate law for a reacti0on is found to be: Rate = k[NO^-₂][I^-][H⁺]² How would the rate of reaction change when
(i) Concentration of H⁺ is doubled
(ii) Concentration of I is halved
(iii) Concentration of each of NO₂^-,I^- and H⁺ are tripled?

25.

A reaction 2X\(\longrightarrow\)Y + 3Z(e.g., 2NH₃\(\longrightarrow\)N₂+3H₂) is being carried out in a closed vessel. The rate of disapppearance of X, \(-{\Delta[X]\over\Delta t}\)is found to be 0.066 mol L^-1s^-1. Calculate \({\Delta[Y]\over\Delta t} \ and \ {\Delta[Z]\over\Delta t}\)

26.

Calculate the electrode potential of the electrode Zn/Zn²⁺ (conc. = 0.1M) at 25^oC Given that E⁰ _Zn,Zn²⁺ = 0.7618 volt.

27.

Two half cells are: AI³⁺(aq) / AI and Mg²⁺ (aq)/ Mg. The reduction potentials of these half cells are -1.66 V and - 2.36 V respectively. Calculate the cell potential. Write the cell reaction also.

Generic 5

3 x 5 = 15

28.

(i) Two liquids X and Y boil at 100°C and 120°C respectively. Which of them has higher vapour pressure at 50°C and why?
(ii) Calculate the boiling point of a solution prepared by adding 15.00 g of NaCI to 250 g water. (K_b for water = 0.512 K kg mol^-1; molar mass of NaCI = 58.44g)
(iii) Calculate the lowering of vapour pressure for 0.1 m aqueous solution of non -electrolyte at 75°C. (\(\triangle\)H = 9.720 K cal mol^-1, P₂ = 742.96 torr)

29.

For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained:

t/s	0	30	60
[CH³COOCH³]/mol L^-1	0.60	0.30	0.15

(i) Show that It follows pseudo first order reaction, as the concentration of water remains constant.
(ii) Calculate the average rate of reaction between the time interval 30 to 60 seconds. [Given log 2 = 0.3010, log 4 = 0.6021]

30.

Two students use same stock solution of ZnSO₄ and a solution of CuSO₄ . The e.m.f. of one cell is 0.03 V higher than the other. The concentration of CuSO₄ in the cell with higher e.m.f. value is 0.5 M. Find out the concentration of CuSO₄ in the other cell (2.303 RT/F = 0.06)

Assertion and reason

8 x 1 = 8

31.

Assertion: The kinetic of the reaction
·        mA+nB+pC→
·        m′X+n′Y+p′Z
·        obeys the rate expression as
·        dxdt=k[A]m[B]n
Reason: The rate of the reaction does not depend upon the concentration of C.
Codes:
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.

32.

Assertion: On increasing dilution, the specific conductance keeps on increasing.
Reason: On increasing dilution, degree of ionisation of weak electrolyte increases and molality of ions also increases.
Codes:
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If both assertion and reason are false

33.

Assertion: Water boils at 373 K as the vapour pressure at this temperature becomes equal to atmospheric pressure.
Reason: Vapour pressure of water is less than 1.013 bar at 373 K.
Codes:
A) Assertion and reason both are correct statements and reason is correct explanation for assertion.
B) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C) Assertion is correct statement but reason is wrong statement.
D) Assertion is wrong statement but reason is correct statement.

34.

Assertion : Solutions having the same osmotic pressure are called isotonic solutions.
Reason : Ca2+ and K+ ions are responsible for maintaining proper osmotic pressure balance in the cells of organism.
Codes:
A) Assertion and reason both are correct statements and reason is correct explanation for assertion.
B) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C) Assertion is correct statement but reason is wrong statement.
D) Assertion is wrong statement but reason is correct statement.

35.

Assertion : \(\mathrm{E}_{\mathrm{Ag}^{+} / \mathrm{Ag}}\) increases with increase in concentration of Ag⁺ ions.
Reason : \(\mathrm{E}_{\mathrm{Ag}^{+} / \mathrm{Ag}}\) has a positive value.
Codes :
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

36.

In the following questions a statement of assertion followed by a statement of reason is given.
Assertion: Rate constants determined from Arrhenius equation are fairly accurate for simple as well as complex molecules.
Reason: Reactant molecules undergo chemical change irrespective of their orientation during collision.
Codes:
(a) Both assertion and reason are correct and the reason is correct explanation of assertion.
(b) Both assertion and reason are correct but reason does not explain assertion.
(c) Assertion is correct but reason is incorrect,
(d) Both assertion and reason are incorrect.
(e) Assertion is incorrect but reason is correct.

37.

Assertion: Amalgam is a homogeneous solution.
Reason: Amalgam is a solution in which mercury is solute and zinc is solvent.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion .
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

38.

In the following questions.an Assertion (A) isfollowed by a corresponding Reason (R) Use the following keys to choose the appropriate answer.
Assertion (A) Solid NaCl does not conduct electricity.
Reason (R) Solid NaCl has no free ions.
Codes:
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

Case Study Questions

3 x 4 = 12

39.

The oxidation number of the central atom in a complex is defined as the charge it would carry if all the ligands are removed along with the electron pairs that are shared with the central atom. Similarly the charge on the complex is the Sum of the charges of the constituent parts, i.e. the sum of the charges on the central metal ion and its surrounding ligands. Based on this, the complex is called neutral if the sum of the charges of the constituents is equal to zero. However, for an anion or cationic complex, the sum of the charges of the constituents is equal to the charge on the coordination sphere.
Based on the above information, answer the following questions.
(a) what is the secondary valence of Co in [Co(NH₃)₄Cl₂]⁺?
(b) What type of isomerism is shown by the complex Cr(H₂O)₆]Cl₃ and [Co(H₂O)₅Cl]Cl₂.H₂O?
(c) Write the electronic configuration of d⁴ ion on the basis of crystal field theory when
(i) \(\Delta_o<P\)
(ii) \(\Delta_o>P\)
Or
(c) Find the oxidation state and coordination number of the central metal ion in [Co(H₂O)(CN)(en)₂]²⁺.

40.

Read the passage given below and answer the following questions:
The solubility of gases increases with increase of pressure. William Henry made a systematic investigation of the solubility of a gas in a liquid. According to Henry's law "the mass of a gas dissolved per unit volume of the solvent at constant temperature is directly proportional to the pressure of the gas in equilibrium with the solution".
Dalton during the same period also concluded independently that the solubility of a gas in a liquid solution depends upon the partial pressure of the gas. If we use the mole fraction of gas in the solution as a measure of its solubility, then Henry's law can be modified as "the partial pressure of the gas in the vapour phase is directly proportional to the mole fraction of the gas in the solution":
(i) Henry's law constant for the solubility of methane in benzene at 298 K is 4.27 X 10⁵ mm Hg. The solubility of methane in benzene at 298 K under 760 mm Hg is

(a) 4.27 x 10^-5	(b) 1.78 x 10^-3
(c) 4.27 X 10^-3	(d) 1.78 x 10^-5

(ii) The partial pressure of ethane over a saturated solution containing 6.56 x 10^-2 g of ethane is 1 bar. If the solution contains 5.00 x 10^-2 g of ethane then what will be the partial pressure (in bar) of the gas?

(a) 0.762

(b) 1.312

(c) 3.81

(d) 5.0

(iii) K_H (K bar) values for Ar_(g), CO_2(g), HCHO_(g)and CH_4(g) are 40.39, l.67, 1.83 x 10^-5 and 0.413 respectively.
Arrange these gases in the order of their increasing solubility.

\(\text {(a) } \mathrm{HCHO}<\mathrm{CH}_{4}<\mathrm{CO}_{2}<\mathrm{Ar}\)	\(\text { (b) } \mathrm{HCHO}<\mathrm{CO}_{2}<\mathrm{CH}_{4}<\mathrm{Ar}\)
\(\text {(c) } \mathrm{Ar}<\mathrm{CO}_{2}<\mathrm{CH}_{4}<\mathrm{HCHO}\)	\(\text { (d) } \mathrm{Ar}<\mathrm{CH}_{4}<\mathrm{CO}_{2}<\mathrm{HCHO}\)

(iv) Which of the following statements is correct

(a) K_H increases with increase of temperature

(b) K_H decreases with increase of temperature

(c) K_H remains constant with increase oftemperature

(d) K_H first increases then decreases, with increase of temperature.

41.

Read the passage given below and answer the following questions:
Standard electrode potentials are used for various processes:
(i) It is used to measure relative strengths of various oxidants and reductants.
(ii) It is used to calculate standard cell potential.
(iii) It is used to predict possible reactions.
A set of half-reactions (in acidic medium) along with their standard reduction potential, E^o (in volt) values are given below
\(\mathrm{I}_{2}+2 e^{-} \rightarrow 2 \mathrm{I}^{-} ; \quad E^{\circ}=0.54 \mathrm{~V}\)
\(\mathrm{Cl}_{2}+2 e^{-} \rightarrow 2 \mathrm{Cl}^{-} ; \quad E^{\circ}=1.36 \mathrm{~V}\)
\(\mathrm{Mn}^{3+}+e^{-} \rightarrow \mathrm{Mn}^{2+} ; \quad E^{\circ}=1.50 \mathrm{~V}\)
\(\mathrm{Fe}^{3+}+e^{-} \longrightarrow \mathrm{Fe}^{2+} ; \quad E^{\circ}=0.77 \mathrm{~V}\)
\(\mathrm{O}_{2}+4 \mathrm{H}^{+}+4 e^{-} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O} ; E^{\circ}=1.23 \mathrm{~V}\)
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following statements is correct?

(a) CI^- is oxidised by O₂	(b) Fe²⁺is oxidised by iodine
(c) I^- is oxidised by chlorine.	(d) Mn²⁺ is oxidised by chlorine

(ii) Mn³⁺ is not stable in acidic medium, while Fe³⁺is stable because

(a) O₂ oxidises Mn²⁺ to Mn³⁺

(b) O₂ oxidises both Mn²⁺ to Mn³⁺ and Fe²⁺to Fe³⁺

(c) Fe^3-oxidises H₂O to O₂

(d) Mn³⁺ oxidises H₂O to O₂

(iii) The strongest reducing agent in the aqueous solution is

(a) I^-

(b) Cl^-

(c) Mn2⁺

(d) Fe²⁺

(iv) The emf for the following reaction is
\(\mathrm{I}_{2}+\mathrm{KCl} \rightleftharpoons 2 \mathrm{KI}+\mathrm{Cl}_{2}\)

(a) -0.82 V

(b) +0.82 V

(c) -0.73 V

(d) +0.73 V

Visit QB365-SLMS - https://www.qb365.in/slms/

Answers Key:

Generic 2

6 x 2 = 12

Higher the value of KH for a gas, lower will be its solubility and vice-versa.

Rate of reaction increases with temperature. Temperature coefficient is the ratio of rate constant at temperature (T + 10) K to the rate constant at temperature TK.
Temperature coefficient
\(=\frac { Rate \ constant \ at \ (T/10)K }{ Rate \ constanr \ at \ TK } \)
It is observed that for a chemical reaction with rise in temperature by 10°, the rate constant is nearly doubled.

\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\text { Conductivity }(k)=\frac{1}{\text { Resistance }(R)} \times \text { Cell constant }\)

k' = k [H₂O]
\(\therefore\) \(\frac { k' }{ { [H }_{ 2 }O] } =\frac { { min }^{ -1 } }{ { molL }^{ -1 } } =L\) mol^-1 min^-1
Thus, it has the units of a second order reaction.

4.99\(\times\)10^-4M

\(A_m={1000\times k\over M}\)
138.9 S cm² mol^-1=\(1000\times k\over 1.5\)
\(k={138.9\times 1.5\over 1000}={208.05\over 1000}={2.0805}\times 10^{-1}\ S\ cm^{-1}\)

Multiple Choice Question

15 x 1 = 15

(b)
exothermic and reversible process

(a)
+k/2.303

(b)
+ 0.77 V

10.

(d)
All of the above

11.

(b)
0.1

12.

(b)
1.0 x10²³ electrons

13.

(b)
0.29/K

14.

(d)
first

15.

16.

(a)
0.25 h

17.

(b)
87%

18.

19.

20.

(b)
Cell emf

21.

\({ N }_{ 1 }{ V }_{ 1 }+{ N }_{ 2 }{ V }_{ 2 }+{ N }_{ 3 }{ V }_{ 3 }={ N }_{ 4 }{ V }_{ 4 }={ N }_{ 4 }({ V }_{ 1 }+{ V }_{ 2 }+{ V }_{ 3 })\)

Generic 3

6 x 3 = 18

22.

Calculation of mole fraction (x_O2)
Mass of 1 L of solution = 1000 g (∵ d = 1 g mL⁻¹)
∴ Mass of solvent (water) =1000g − 0.05g ≅ 1000g
∴ nH₂O = \(\frac{1000g}{18 g mol ^ {−1}}\)= 55.5 moles, nO₂= \(\frac{0.05g}{32 gmol ^{-1}}\) = 1.56 × 10⁻³mole
∴ x_O2= n_O2 /n_O2+n_H2O ≅ n_O2/ n_H2O = 1.56 × 10⁻³/ 55.5 = 2.81 × 10⁻⁵
Calculation of partial pressure. Applying Henry's law,
p_O2= K_H× \(\chi\)O₂ = (34.86 × 10³ bar) × (2.81 × 10⁻⁵) = 0.98 bar.

23.

\({ \pi }_{ cane\ sugar }={ \pi }_{ X }\)
Therefore, c_{cane sugar}=c_X
(where c is molar concentration)
\(\frac { { W }_{ cane\ sugar } }{ { M }_{ cane\ sugar } } =\frac { { W }_{ X } }{ { M }_{ X } } \)
\(\frac { 5g }{ 342 \ g \ { mol }^{ -1 } } =\frac { 0.877 }{ { M }_{ X } } \)
\(\\ \Rightarrow { M }_{ X }=\frac { 0.877\times 342 }{ 5 } g\ { mol }^{ -1 }\)
\(\Rightarrow { M }_{ X }=59.9 \ or \ 60 \ g{ \ { mol }^{ -1 } }\)

24.

(i) 4 times
(ii) halved
(ii) 81 times.

25.

\({\Delta[Y]\over\Delta t}\)= 0.033 mol L^-1s^-1

\({\Delta[Z]\over\Delta t}\)= 0.099 mol L^-1s^-1

26.

E⁰ _Zn^2+,Zn = -0.7914volt.

27.

0.70 V, 3Mg + 2 AI³⁺ \(\longrightarrow\) 3 Mg²⁺ + 2 AI

Generic 5

3 x 5 = 15

28.

(ii) Calculation of elevantion in b.p. temperature (ΔT_b) NaCI dissociates in aqueous solution as NaCl (s)→Na⁺ (aq)+Cl⁻(aq)
i = 2, W_B = 15.0g, M_B = 58.44 g mol⁻¹,W_A= 250g = 0.25kg
K_b= 0.152 K kg mol^{−1

\(\Delta T_{b}=i \times K_{b} \times m=\frac{i \times K_{b} \times W_{B}}{M_{B} \times W_{A}}\)

\(\Delta T_{b}=\frac{2 \times\left(0.512 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right) \times(15.0 g)}{\left(58.44 \mathrm{~g} \mathrm{~mol}^{-1}\right) \times(0.25 K g)}=1.05 K\)}
Step II. Calculation of boilling point of solution (Tb)
^{\(T_{b}=T_{b}^{\circ}+\Delta T_{b}=(373+1.05) K=374.05 K \)}

29.

For the first order reaction
\(t_1=30sec\)
\(t_2=30sec\)
\(k_1=\frac{2.303}{t_1}\log \frac{a}{(a-x)}\)
\(\Rightarrow\ \ \ \ k_1=\frac{2.303}{30}\log \frac{0.60}{0.30}\)
\(=\frac{2.303}{30}\log 2\)
\(\Rightarrow\ \ \ \ k_1=\frac{2.303}{30}\times 0.3010\)
\(=0.0231 \ s^{-1}\)
and \(k_2=\frac{2.303}{t_2}\log \frac{a}{(a-x)}\)
\(=\frac{2.303}{60}\log \frac{0.60}{0.15}\)
\(=\frac{2.303}{60}\log 2^2\)
\(\Rightarrow\ \ k_2=\frac{2.303\times 2 \times 0.3010}{30}\)
\(=0.0231\ s^{-1}\)
\(\because\ k_1=k_2\)
Hence, the reaction is pseudo first order reaction.
(ii) \(Rate=\frac{\Delta x}{\Delta t}\)
\(=\frac{0.30-0.15}{60-30}=\frac{0.15}{30}\)
\(=0.005 \ mol\ L^{-1} \ s^{-1}\)

30.

The two cells may be represented as
Zn I Zn²⁺(cone = c) II Cu²⁺(c = ?) I Cu, EMF = E₁
Zn I Zn²⁺(cone = c) II Cu²⁺(0·5 M) I Cu, EMF = E₂
The cell reaction is : Zn + Cu²⁺⇾ Zn²⁺+ Cu
\(E_1=E^0-{2.303\ RT\over 2F}log{c\over [Cu^{2+}]}\)
\(E_2=E^0-{2.303\ RT\over 2F}log{c\over 0.5}\)
\(E_2-E_1={2.303\ RT\over 2F}\left( log{c\over [Cu^{2+}]}-log{c\over 0.5}\right)=0.03V\)
\({0.06\over 2}log{0.5\over [Cu^{2+}]}=0.03\ or\ log{0.5\over [Cu^{2+}]}=1\ or\ {0.5\over {[Cu^{2+}]}}=10\ or\ [Cu^{2+}]={0.5\over 10}=0.05M\)

Assertion and reason

8 x 1 = 8

31.

A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
Explanation:
Rate expression
dxdt=K[A]m[B]n

32.

(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
Explanation:
On increasing dilution specific conductance increases because it is directly proportional to dilution. When more amount of solvent such as water is added to the solution, it results in dissociating the molecules into ions of a weak electrolyte. Thus, the degree of ionisation of weak electrolyte increases upon dilution. The mobility of ions will also increase because the ions will get the more free space to move. Thus, both assertion and reason are correct but reason is not the correct explanation of assertion.

33.

C) Assertion is correct statement but reason is wrong statement.
Explanation:
At373 K(100∘C), the vapour pressure of water is equal to 1 atmospheric pressure which is 1.013 bar.

34.

C) Assertion is correct statement but reason is wrong statement.
Explanation:
Sodium ion, Na+ and potassium ion, K+ are responsible for maintaining proper osmotic pressure balance inside and outside of the cells of organisms.

35.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

36.

37.

(b): In amalgam, solute and solvent are uniformly distributed.

38.

(a)Solid NaCI does not conduct electricity due to the absence of free ions. Thus, both (A)and (R)are correct and (R) is the correct explanation of (A).

Case Study Questions

3 x 4 = 12

39.

(a) The secondary valency of Co in [Co(NH₃)₄CI₂]⁺ complex is 6.
(b) Hydrate isomer is shown by the given complex
[Cr(H₂O)₆]Cl₃ and [Cr(H₂O)₅Cl]Cl₂.H₂O.
These type of isomerism arises in case where water is involved as a solvent.
(c) (i) For d⁴ ions, if \(\Delta\)_o<P, the fourth electron enters one of the e_g orbitals giving the configuration \(t_{2 g}^3 e_g^1\).
(ii) For d⁴ ion, if \(\Delta\)_o > P, the fourth electron occupy t_2g orbital with configuration \(t_{2 g}^4 e_g^0\).
Or
(c) In [Co(H₂O)(CN)(en)₂]³⁺ two ethylenediamine molecules, one H₂O molecule and one CN atom are linked. Since, ethylenediamine acts as a bidentate ligand while, H₂O and CN are unidentate, thus the coordination number of Co is 6.
Let, the oxidation state of Co be x.
\(\therefore\) x + 0 - 1 + 0 = + 2
x = +3
Thus, the oxidation state of Co is +3

40.

(i) (b): K_H = 4.27 x 10⁵ mm Hg
P = 760mm Hg
According to Henry's law, \(p=K_{\mathrm{H}} \times x_{\mathrm{CH}_{4}}\)
\(x_{\mathrm{CH}_{4}}=\frac{p}{K_{\mathrm{H}}}=\frac{760}{4.27 \times 10^{5}}=1.78\ \times 10^{-3}\)
(ii) (a): According to Henry's law, m = K_H x P
6.56 X 10^-2 = K_H X 1
K_H = 6.56 X 10^-2
For another case,5x 10^-2 = 6.56 X 10^-2 x P
\(p=\frac{5 \times 10^{-2}}{6.56 \times 10^{-2}}=0.762 \mathrm{bar}\)
(iii) (c) : Higher the value of K_H at a given pressure, the lower is the solubility of the gas.
(iv) (a)

41.

(i) (c) : The half cell having the higher reduction potential will undergo reduction process.
(ii) (d) : Electrode potential of Mn³⁺ is higher than O₂.
(iii) (a) : Due to least electrode potential value.
(iv) (a) : Half reactions :

\(\mathrm{I}_{2}+2 e^{-} \rightarrow 2 \mathrm{I}^{-}\)	Reduction E^o = 0.54 V
\(2 \mathrm{Cl}^{-} \longrightarrow \mathrm{Cl}_{2}+2 e^{-}\)	Oxidation E^o = -1.36 V
	-------------------------------
	e.m.f = -0.82 V