CBSE Set Q Chemistry Sample Test Papers For Class 12th for students online

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Chemistry Class - XII  (CBSE)
You are on questions 1 to 20 of Set I

Q.1 State the physical significance of 2. (1 mark)

Q.2 Write which one out of O+2 and O--2 is more stable? (1 mark)

Q.3 Write an expression in the form of a chemical equation for standard enthalpy of formation of for CO? (1 mark)

Q.4 Write an expression to relate molar conductivity of an electrotype to its degree of dissociation? (1 mark)

Q.5 What is the 'ambident group' ? Give an example. (1 mark)

Q.6 Indicate a chemical reaction involving a homogeneous catalyst ? (1 mark)

Q.7 Mention two main function of carbohydrates in plants ? (1 mark)

Q.8 How many sigma bonds are present in 3-methylphenol ?(1 mark)

Q.9 Mention the chief reason for the resemblance between beryllium and aluminium ? (1 mark)

Q.10 Mention two important uses of sulphuric acid ? (1 mark)

Q.11 What is energetically achieved by coupling reaction in biological system? Explain. (1 mark)

Q.12 What types of substance generally constitute a chemical propellant? Briefly describe the function of rocket propellant. (2 marks)

Q.13 The ionisation energy of hydrogen atom is 1.312x106 J mol-1. Calculate the energy required to excite the electron in a hydrogen atom from the ground state to the first excited state. (Avagadro constant=6.022x1023 mol-1)
(2 marks)

Q.14 Describe briefly two important function of nucleic acid. (2 marks)

Q.15 Calculate the free energy change when one mole of sodium chloride is dissolve in water at 298K.
(Given : Lattice energy of NaCl= -777.8 kj mol-1, Hydration energy of NaCl= -774.1kj mol-1 and S at 298 K = 0.043 K-1mol-1. (1 mark)

Q.16 For the equilibrium PCl5(g) <=== PCl5(g) + Cl2(g) at 298 K, K=1.8x10-7. Calculate Go for the reaction. (R=8.314JK-1mol-1). (1 mark)

Q.17 The freezing point of pure nitrobenzene is 278.8 K. When 2.5gm of an unknown substance is dissolve in 100gm of nitrobenzene, the freezing point of the solution is found to be 276.8K. If the freezing point depression constant of nitrobenzene is 8.0K Kg mol-1, what is the molar mass of unknown substance? (2 marks)

Q.18 For the reaction, 2A+2B+C----- A2B+C, rate law has been determined to be: rate = k[A][B]2. If the rate constant, k = 2.0x10-6 mol-6L2 and [C]=0.8 mol L-1? (2 marks)

Q.19 For the reaction NO2(g)+ CO(g)-----CO2(g) + NO(g) the approximately determined rate expression below 400K is rate = k[NO]2 what mechanism can be proposed for above reaction. (2 marks)

Q.20 write IUPAC name of the following compounds :
(i) (CH3)3C.CH2.CH2Cl
(ii) CH3.CH.CH.CH.CHO (2 marks)

Q.21 Explain the mechanism of the acid-catalysed dehydration of ethanol at high temperature. (2 marks)

Q.22 Comment on the structural difference between thermoplastics and thermosetting polymers. (2 marks)

Q.23 What are micels? Given an example of a micellar system. (2 marks)

Q.24 Consider the given standard potentials (in volts)in 1 M acidic solution :
Fe2+/Fe, -0.4 V ; Fe3+/Fe2+, +0.8 V
Mn2+/Mn, -1.2 V ; Mn3+/Mn2+, +1.5 V
(i) Comment on the relative stabilities of +2 and +3 oxidation states of iron and manganese;
(ii) Which of the two metals may be more easily oxidised to +2 state?
(2 marks)

Q.25 Account for the following statements : (2 marks)
(i) Co(II) is stable in aqueous solution but in the presence of strong ligands and air it can get oxidised to Co(III). (Atomic number Co=27)
(ii) One among the lanthanide's,Ce(III) can be easily oxidised to Ce(IV). (Atomic No : Ce=58).

Q.26 Write an equation in ionic form to represent the oxidising action of Cr2O2-7 in acidic medium. Also draw the structure of Cr2O2-7. (2 marks)

An element of atomic mass 98.5g mol-1 occurs in fcc structure. If its unit cell edge length is 500pm and its density is 5.22g cm-3, what is the value of Avagadro Constant? (3 marks)

Q.28 One litre aqueous solution of sucrose (molar mass=342g mol-1) weighing 1015g is found to record an osmotic pressure of 4.82 atom at 293k. What is the molarity of the sucrose solution? (R=0.0821 atom mol-1K-1)
(3 marks)

Q.29 Calculate the potential of the following cell reaction at 298K :
Sn4+(1.50M) + Zn(s) --- Sn2+(0.50M) + Zn2+(2.0M)
The standard potential Eo of the cell is 0.89 V. Whether the potential of the cell will increase or decrease, if the concentration of Sn4+ is increased in the cell? (R = 8.314JK-1 mol-1; F=96,500 C mol-1) (3 marks)

Q.30 (a) How many b -particles are emitted in the decay series :
238 U92 --- 206 Pb82 ?
(b) Complete the following nuclear reaction :
(i)2713 Al + 42 H -- 3015 Pb + .....
(ii)23592 U + 10n -- 14056+.....+ 210n (3 marks)

Q.31 How are the following conversions accomplished? (Write reaction only)
(i) Aniline to Chloro-benzine
(ii) Nitrobenzene to phenol
(iii) Aniline to benzoic acid (3 marks)

Q.32 Select the complex formation reaction and write an expression for the stability constant of the complex species. What information is conveyed regarding the strength of ligands from the stability constant values of their complexes with a metal ion? Illustrate your answer with example of monodentic ligands. (3 marks)

Q.33 (a) Explain giving reason each of he following :
(i) CCl4 remains unaffected whereas SiCl4 is easily hydrolysed by water.
(ii) Nitrogen exists as a diatomic molecule, N2, whereas phosphorus exists as tetra-atomic molecule, P4.
(iii) SF6 is known but SH6 not known.
(b) Write the balance equation fro the following reaction :
(i) B2H6 + LiH ---
(ii) BrO3 + F2 + OH---- (5 marks)

Q.34 (a)You are provided with 4 reagent :
LiAlH4, I2/NaOH, NaHSO3 and Sciff's reagent. Write which two reagents can be used to distinguish between the compounds in each of the following pairs :
(i) CH3CHO and CH3COCH3
(ii) CH3CHO and C6H5CHO
(iii) C6H5COCH3 and C6H5COCH3 and C6H5COC6H5
(b) Account for the following :
(i) The order of reactivity of halogen acids with ether is HI HBr HCl
(ii) The pKa value of choloroacetic acid is lower than the pKa value of acetic acid. (5 marks)


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