Kerala Class 12 First Term Question Paper 2023 Chemistry

Kerala Board

First Term
Question Paper

Name: …………………………………
Roll No. ……………………………….

SECOND YEAR HIGHER SECONDARY
FIRST TERMINAL EXAMINATION AUGUST– 2023
Part – III Time : 2 Hours

CHEMISTRY Cool-off time : 15 Minutes

Maximum : 60 scores

General Instructions to Candidates :

• There is a ‘Cool-off time’ of 15 minutes in addition to the writing time.
• Use the ‘Cool-off time’ to get familiar with questions and to plan your answers.
• Read questions carefully before answering.
• Read the instructions carefully.
• Calculations, figures and graphs should be shown in the answer sheet itself.
• Give equations wherever necessary.
• Electronic devices except non-programmable calculators are not allowed in the
Examination Hall.

Answer any four questions from 1 to 5. Each carry 1 score. (4  1 = 4)

1. Number of moles of the solute per kilogram of the solvent is called …………
(a) Mole fraction (b) Molality (c) Molarity (d) Molar mass
2. What is the charge of 1 mol of electron?
3. Write the unit of rate constant for a zero order reaction.
4. The limiting molar conductivity of weak electrolytes can be calculated by which of the following
law?
(a) Faraday’s law (b) Kohlrausch law (c) Henry’s law (d) Raoult’s law
5. Name a first-row transition element which does not exhibit variable oxidation states.

Answer any eight questions from 6 to 15. Each carry 2 scores. (8  2 = 16)

6. Write any one difference between primary cell and secondary cell. Write one example for each.
7. For intravenous injections only solutions with osmotic pressure equal to that of 0.9%
(mass/volume) NaCl solution is used. Why?

8. The conversion of a molecule A to B follows second order kinetics.
a) Write the rate equation for this second order reaction. (1)
b) If the concentration of A is increased to three times, how will it affect the rate of formation
of B. (1)
9. 0.4 g of a non-volatile, non-electrolyte solute dissolved in 20 g of benzene lowers its freezing
point by 0.75 K. The freezing point depression constant for benzene is 5.12 K kg mol-1. Calculate
the molar mass of the solute.
10. Draw the structures of chromate and dichromate ions.
11. Derive an expression for the half-life period of a first order reaction.
12. What is reverse osmosis? Write any one of its applications.
13. Transition elements are used as catalyst in many reactions. What are the reasons for their
catalytic property?
14. Calculate the limiting molar conductivity of acetic acid (HAc). Given that Λ0m for NaCl, HCl and
NaAc are 126.4, 425.9 and 91.0 S cm2 mol-1 respectively.
15. The standard electrode potential for Daniel cell is 1.1 V. Calculate the standard Gibbs Energy
change for the reaction: Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s).

Answer any eight questions from 16 to 26. Each carry 3 scores. (8  3 = 24)

16. For ethanol-acetone mixture solute-solvent interaction is weaker than solute-solute and
solvent-solvent interaction.
a) Does this solution obey Raoult's law? (1)
b) Draw the vapour pressure - mole fraction graph for this solution. (2)
17. The cell reaction in Daniel cell is Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) and Nernst equation for
electrode potential for the general electrode reaction Mn+(aq) + ne- → M(s) is
EMn+| M = E0Mn+| M – 2.303RT log 1
nF [Mn+]
Derive Nernst equation for Daniel cell.
18. a) What is abnormal molar mass? (1)
b) Complete the following table by giving the values of van't Hoff factor ‘i’ for complete
dissociation of solute. (2)

Salt van’t Hoff factor ‘i’ for complete
dissociation of solute

KCl
Al(NO3)3
Na2SO4
Al2(SO4)3

19. The rusting of iron can be considered as due to the formation of electrochemical cells on its
surface.
(a) Write the anodic and cathodic reactions taking place during rusting. (2)
(b) Write any two methods used to prevent the corrosion of iron. (1)
20. How do you prepare K2Cr2O7 from chromite ore?
21. Write any 3 differences between order and molecularity of a reaction.
22. (a) Describe about standard Hydrogen Electrode (SHE). (2)
(b) The emf of the cell obtained by coupling an electrode with SHE is 1.37V. If SHE is the
negative electrode, find the electrode potential of the given electrode. (1)
23. The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate
the energy of activation of the reaction assuming that it does not change with temperature.
24. Among the following transition metal ions, identify the ions which are coloured in aqueous
solution. Justify your answer.
Fe2+, Sc3+, Ni2+, Cu+
25. a) Name the two types of magnetic behaviour exhibited by transition metals. (1)
b) Calculate the ‘spin only’ magnetic moment of M2+(aq) ion (Z = 27). (2)
26. a) What is pseudo first order reaction? Write one example. (2)
b) Examine the graph given below and identify the order of the reaction corresponding to it. (1)

Answer any four questions from 27 to 31. Each carry 4 scores. (4  4 = 16)

27. a) What are colligative properties? (2)

b) Write the names of any two colligative properties. (1)
c) Which colligative property measurement is the best for determining the molar mass of
proteins? (1)

28. a) What are fuel cells? (1)
b) Write the cathode and anode reactions of H2 – O2 fuel cell. (2)
c) Write any one advantage of fuel cell over other conventional cells? (1)
29. a) What are Azeotropes? (1)
b) Vapour pressure of pure chloroform (CHCl3) and dichloromethane (CH2Cl2) at 298 K are
200 mm of Hg and 415 mm of Hg respectively. Calculate the vapour pressure of the solution
prepared by mixing 24 g of chloroform and 17 g of dichloromethane at 298 K. (3)
30. a) Write Arrhenius equation. Explain the terms in it. (2)
b) Calculate the time required for the 90% completion of a first order reaction if k = 0.2303 s-1.
(2)
31. a) What is Lanthanoid contraction? Give reason for it? (2)
b) Write any two consequences of Lanthanoid contraction. (2)

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