» CBSE Chemistry Sample Question Paper - Year 1998 : CBSE Sample Question Papers

Chemistry Class - XII (CBSE)
You are on Set no 1 Q.No. 1 to 20

Time allowed : 3 hours
Maximum Marks : 70

General Instructions :

(i) All questions are compulsory.
(ii) Marks for each question are indicated against it.
(iii) Question number 1 to 10 are very short-answer questions each of 1 mark. Answer them in about one sentence each.
(iv) Question number 11 to 26 are short-answer questions of 2 marks. Answer them in not more than 30 words each.
(v) Question number 27 to 32 are short-answer questions of 3 marks. Answer them in not more than 40 words each.
(vi) Question number 33 to 34 are long-answer questions of 5 marks each. Answer them in not more than 70 words each.
(vii) Use Log tables, if necessary.
(viii) Please write down the serial number of the question before attempting it.

Q1) Write the MO electronic configuration of a diatomic molecule having a bond order of three ? (Marks 1)

Q2) What are non-stoichiometric compounds ? (Marks 1)

Q3) Complete the nuclear reaction expression ? (Marks 1)

₂₀Co⁵⁹ (d,p)……

Q4) Write the IUPAC name of (Marks 1)

Image no.1

Q5) Why do noble gases form compounds with fluorine and oxygen only ? (Marks 1)

Q6) Why is hydrochloric acid not used to acidify a permanganate solution in volumetric estimations of Fe²⁺ or C₂O₄^2-? (Marks 1)

Q7) How many isomers are there for the complex [Co(NH₃)₄ Cl₂]Cl? (Marks 1)

Q8) Why are carbohydrates generally optically active? (Marks 1)

Q9) Give one important use of each of the following in pharmacy : (Marks 1)
(i) Equanil
(ii) Morphine

Q10) Illustrate the function of mordent’s by one example. (Marks 1)

Q11) Predict the structure of M_gO crystal and co-ordination number of its cation in which the cation and anion radii are equal to 65 pm and 140 pm respectively. (Marks 2)

Q12) With the help of suitable diagrams, illustrate the two types of non-ideal solutions. (Marks 2)

Q13) What is meant by average bond energy? In what way is it different from bond energy of a diatomic molecule ? Give suitable examples. (Marks 2)

Q14) Explain Kohlrausch’s law of independent migration of ions. Mention one application of Kohlrausch’s law. (Marks 2)

Q15) For what concentration of Ag⁺ (aq) will the e.m.f. of the given cell be zero at 25oC, if concentration of Cu²⁺ (aq) is 0.1 M? (Marks 2)
CU (s) | Cu²⁺ (0.1 M) || Ag⁺ (aq) | Ag (s)

[ Given Eo _Ag⁺_/Ag = + 0.80 V; Eo _Cu²⁺_/Cu = + 0.34 V ]

Q16) (a) Show graphically how the rate of a first order reaction with only one reactant depends upon the concentration of the reactant.
(b) Give one example of a first order reaction. (Marks 2)

Q17) For a reaction, the energy of activation is zero. What is the value of rate constant at 300 K, if k = 1.6 x 10⁶ _s^-1 at 280 K ? [ R = 8.31 JK^-1 mol^-3 ] (Marks 2)

Q18) 1.0 x 10^-6 g of radioactive iodine is injected into the blood of a patient. How long will it take for radioactivity to fall to 10% of the initial value?
[ Given t_1/2 for ₅₃I¹³³ = 8.05 days ] (Marks 2)

Q19) Account for the following :
(i) Formaldehyde gives Cannizaro’s reaction whereas acetaldehyde does not.
(ii) Carboxylic acids do not give the characteristic reactions of carbonyl group. (Marks 2)

Q20) How are the following conversions carried out?
(i) Ethanoic acid to propanoic acid.
(ii) Ethanol to propanone.
Write reaction equations and conditions to support your answer. (Marks 2)

Q21) Give an example of each with necessary reaction conditions :
(i) Sandmeyer’s reaction
(ii) Kharasch Effect (Marks 2)

Q22) What is ‘inert pair effect’? Discuss the oxidation states of Group 13 elements in relation to this effect. (Marks 2)

Q23) A co-ordination compound has the formula CoCl₃.4NH₃. It does not liberate ammonia but precipitates chloride ions as silver chloride. Give the IUPAC name of the complex and write its structure formula. (Marks 2)

Q24) Write the information asked for in the following polymers :
(i) Bakelite : material used for preparation
(ii) Synthetic rubber : monomer unit
(iii) PVC : monomer unit
(iv) Nylon-66 : materials required for preparation. (Marks 1)

Q25) “The two strands of DNA are not identical but are complementary.” Explain this statement. (Marks 2)

Q26) Write the structure of adenosine triphosphate indicating clearly the energy rich bonds. How does this molecule form the source of energy? (Marks 2)

Q27) Explain how an electron can be considered to have a particle as well as nature. A moving electron has 4.9 x 10^-25 joules of kinetic energy. Find out its De Broglie wavelength.
(Given h = 6.6x10^-34 Js; m = 9.1x10^-31 kg) (Marks 3)

Q28) An aqueous solution freezes at 272.4 k, while pure water freezes at 273.0 K. Determine :
(i) the molality of the solution,
(ii) boiling point of the solution,
(iii) lowering of vapour pressure of water at 298K.
[ Given K_f = 1.86 K kg mol^{-, K_b = 0.512 K kg mol-1 and vapour pressure of water at 298 K = 23.756 mm Hg ] (Marks 3)}

Q29) (a) When NH₄NO₂ (s) decomposes at 373 K, it forms N₂(g) and H₂O(g). The H for the reaction at one atmosphere pressure and 373k is -223.6 kJ mol^-1 of NH₄NO₄(s) decomposed. What is the value of E for the reaction under the same conditions?
[ Given R = 8.31 JK^- mol^-1 ]
(b) Account for the fact that E is numerically bigger H in the above case. (Marks 3)

Q30) What is meant by the colloidal state of matter? Explain the following terms :
(i) Multi-molecular colloids
(ii) Elector-dialysis (Marks 3)

Q31) An organic compound A having molecular formula, C₆H₆O give a characteristic colour with aqueous FeCl₃ solution. A on treatment with CO₂ and NaOH at 400 K under pressure gives B which on acidification gives a compund C. C reacts with acetyl chloride to give D which is a popular pain-killer. Deduce the structures of A, B, C and D (Marks 3)

Q32) (a) Write the balanced equations for the following reactions :
450 K
(i) BF3 + LiH
(ii) NH3 + NaOCl
(iii) SiCl4 + H2O
(iv) XeF6 + KF
(b) State the reason for the occurrence of “diagonal relationship” in the periodic table. (Marks 3)

Q33) (a) Write the general formula for nitroalkanes and for alkyl nitrites.
(b) How are nitroalkanes prepared alkanes?
© What happens when :
(i) nitroethane is treated with lithium aluminium hydride,
(ii) nitrobenzene is reduced with hydrogen using copper oxide as catalyst.
(d) Write two use of nitroalkanes, one each in the laboratory and in the industry. (Marks 5)

Q34) (a) (i) What are inner transition elements? Write their general electronic configuration.
(ii) In what way are the observed oxidation states of the lanthanide’s related to their electronic configuration?
(b) Describe the general characteristics of the transition elements with special reference to their tendency to :
(i) exhibit paramagnetism,
(ii) form complex compounds,
(iii) their catalytic behaviour. (Marks 5)