CBSE Sample Paper for Class 11 Chemistry
Annual Examination (2020-21)
- This question paper comprises four Sections – A, B,C and D. There are 37 questions in the question paper. All questions are compulsory.
- Section A – Questions no. 1 to 20 are very short answer type questions carrying 1 mark each. Answer these questions in one word or one sentence.
- Section B – Questions no. 21 to 27 are short answer type questions, carrying 2 marks each.
- Section C –Questions no. 28 to 34 are long answer type-I questions, carrying 3 marks each.
- Section D –Questions no. 35 to 37 are long answer type-II questions, carrying 5 marks each.
- There is no overall choice in the question paper.
Q. Read the passage given below and answer questions 1 to 5 that follows-
Buffer solutions plat an important role in a number of biological as well as industrial process. We can prepare buffer solutions of different pH values by selecting suitable concentrations of a weak acid and its salt with a strong base or a weak base and its salt with a strong acid. There are also many single salts whose solutions act as buffers. The ph of acidic buffers can be calculated using Henderson equation. Likewise a similar equation is used for the calculation of pH of basic buffers.
1- What is a buffer?
2- Give one example of a single salt whose solutions acts as a buffer.How does it acts as a buffer?
3- Which buffer is present in our blood? What is the pH value of this buffer?
4- By how much value will the pH of the acidic buffer of CH3COOH+CH3COONa change if concentration of salt is doubled?
5- What do you understand By ‘Buffer capacity” or “Buffer index”?
6- Write the IUPAC name of the element with Z=120(not yet discovered).
7- Find out oxidation no of oxygen in K2O2 and KO2.
8- Name the alkali metal which emits longest wavelength of light in flame test.
9- Name the element of group 13 which shows maximum inert pair effect.
10- Write the product of reduction OF 2-butyne with Na in liquid NH3.
11- Given the IUPAC name of the compound
12- What is the maximum no of electrons which can be accommodated in an atom in which the highest principal quantam no is 4 ?
13- 5mole of gas A and x mole of gas B exert a pressure of 200 Pa in a container of volume 10 m3 at 1000k. Given R is the gas constant in JK-1mol-1, x is-
14- Based on first law of thermodynamics, which one of the following is correct ?
i) For an isochoric process, ∆U=-q
ii) For an adiabatic process,∆U=-w
iii) For an isothermal process,q=+w
iv) For a cyclic process,q=-w
15- Which of the following combination will produce H2 gas-
i) Cu metal and conc.HNO3
ii) Zn metal with NaOH(aq)
iii) Au metal and NaCN(aq) in present of ore
iv) Fe metal and conc.HNO3
For questions number 16 to 20, two statements are given – one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (i), (ii), (iii) and (iv) as given below:
(i) Both Assertion (A) and Reason (R) are correct,statements, and Reason (R) is the correct explanation of the Assertion (A).
(ii) Both Assertion (A) and Reason (R) are correct statements, but Reason (R) is not the correct explanation of the Assertion (A).
(iii) Assertion (A) is correct, but Reason (R) is incorrect statement.
(iv) Assertion (A) is incorrect, but Reason (R) is correct statement.
16- Assertion:Of all the halogen,Fluorine is the most electronegative element. Reason:Fluorine has most negative electron gain enthalpy.
17- Assertion:The water gas shift reactiob can be used to increase the amount of H2 in the syngas mixture.
Reason:In the reaction,CO reduces steam to H2
18- Assertion : First ionisation enthalpy of Galium is higher than aluminium.
Reason : Weak sheliding effect of 3d subshell is Galium.
19- Assertion (A): SF6 molecule is unstable.
Reason (R): A stable molecule must have 8 electrons around the central atom. i.e. octet rule should be satisfied.
20- Assertion (A): Pi bond is never formed alone. It is formed along with a sigma bond.
Reason (R): Pi bond is formed by sideway overlap of p- orbitals only
21- Arrange the following ions in order of increasing ionic radii:Li+,Mg+2,K+,Al+3.
22- Which out of NH3 and NF3 has highest dipole moment and why ?
23- carbon monoxide gas is more dangerous than carbon dioxide gas.Why ?
24- Nitric acid avts only as an oxidizing agent while nitrous acid acts both as an oxidising as well as reducing agent. Explain why ?
25- Density of a gas is found to be 5.46g/dm3 at 270C and 2 bar pressure . What will be its density at STP ?
26- Explain following:
i) Of all alkali metals lithium chloride has the lowest melting point.
ii) Lithium has the highest ionization energy among alkali metals .yet it is the strongest reducing agent.
27- Balance the following redox reactions by ion electron method.
P4(s) +OH–(aq) ——————PH3(g)+H2PO2–
28- (a)At 450K.Kp=2.0*1010bar for the following reaction at equilibrium:
2SO2(g) + O2(g)———–2SO3(g)
What is Kc at this temperature ?
(b) The ionic product of water at 310K is 2.7*10-14. What is the pH of neutral water at this temperature?
(c) The solubility product of AgCl in water is 1.5*10-10. Calculate its solubility in 0.01M NaCl aqueous solution.
29- (a)What will be the mass of one C12 atom in g ?
(b)Determine the molecular formula of an oxide of iron in which the mass percent of iron and oxygen are 69.9 and 30.1 respectively.Given that the molar mass of the oxide is 159.8 gmol-1(Atomic mass:fe=55.85, O=16.000amu)
30- Calculate the enthalpy change for the process
CCl4(g) —————C(g) +4Cl(g) and calculate bond enthalpy of C-Cl in CCl4 (g)
Given: ∆vap H0(CCl4)=30.5KJmol-1, ∆fH0 (CCl4)=-135.5KJmol-1 ∆aH0(C)=715.0KJmol-1, ∆aH0 (Cl2)=242KJmol--1.
31- (i) Write chemical reaction to justify that hydrogen peroxide can function as an oxidisingas well as reducing agent.
(ii) calculate the strength of 10 Volume hydrogen peroxide solution.
32- (a)What is the difference between molality and molarity ?
(b)Dinitrogen and dihydrogen react with each other to produce ammonia according to the chemical equation:
N2(g) + 3H2 (g) ———–2NH3(g)
i) Calculate the mass of ammonia produced if 2.00*103g dinitrogen reacts with 1.00*103g dihydrogen.
ii) Will any of the two reactants remain unreacted?
iii) If yes,Which one and what would be its mass?
33- Give reasons for the following:
i) (SiH3) 3N is a weaker base than N(CH3) 3.
ii) SnCl2 is a reducing agemt while PbO2 is an oxidising agent.
iii) CO2 is a gas but SiO2 is a solid.
34- (i) Write down the products of ozonolysis of 1,2-dimethylbenzene.How does the result support kekule structure of benzene?
ii) Out of Cyclopentadienyly cation and cyclopentadienyl anion which one is aromatic ? comment.
35- Write the molecular orbital configuration of the species:
N2 N2 +` N2 – N2 2-
i) Calculate their bond orders.
ii) Predict their paramagnetic behavior.
iii) Which of these shows highest paramagnetism?
36- Give reason for the following;
i) H2O has higher boiling point than HF.
ii) Ice floats on the surface of water.
iii) Ethyl alcohol has higher boiling point (351K) than ethylamine(290K)
iv) KHF2 exists but KHCl2 does not.
v) Boiling point of HCl is less than HF as well as HBr.
37- (i) Write the state of Hybridization of all the carbon atom in CH2=C=CH2.
ii) Write the structures and IUPAC names of the functional isomers having the molecular formula C2H5O2
iii) Out of HO- and HS- which one is a better nucleophile and which one is a better base ?
iv) The mass of an electron is 9.1*10-31 If its K.E. is 3.0*10-25J. Calculate its wave length.
v) Dehydration of alcohols is always carried out with conc.H2SO4 and not with HCl. Explain.