Practice Paper
TERM II (2021 – 2022)
Class – XI
Chemistry (043)
Time: 2 hours Maximum Marks: 35
General Instructions:
1. There are 12 questions in this question paper with internal choice.
2. SECTION A – Q. No. 1 to 3 are very short answer questions carrying 2 marks each.
3. SECTION B – Q. No. 4 to 11 are short answer questions carrying 3 marks each.
4. SECTION C- Q. No. 12 is case based question carrying 5 marks.
5. All questions are compulsory.
6. Use of log tables and calculators is not allowed
SECTION – A
1. Consider the following acid base equilibrium:
H2SO4 (aq) + CH3COO– (aq) ________ CH3COOH (aq) + HSO4–(aq)
Write the two conjugate acid-base pair in the given equilibrium
2. An alkali metal nitrate (A) when heated strongly produces a brown gas (B). Identify the compound A and B and write the complete reaction.
3. The solubility product of silver carbonate at 298 K is Ag2CO3 is 8 x 10-12. Calculate the solubility of the salt.
SECTION – B
4. An alkene ‘A’ on ozonolysis gives two moles an aldehyde ‘B’ having molecular formula C2H4O.
(a) Write the IUPAC name of A and B
(b) Draw the geometrical isomers of alkene A. Which isomer is non polar and why?
OR
Rotation around C-C single bonds in an alkane leads to different spatial arrangements
(a) Predict the total number of conformation of ethane molecule?
(b) Which conformation of ethane has lowest torsional strain?
(c) Is it possible to separate the extreme conformations of ethane? Give reason.
5. (a) Write van-der-waal Equation of state for n moles of gas.
(b) If the pressure correction factor in the van-der-waal equation for one mole is neglected then what will be value of compressibility factor? Mention the nature of deviation shown by the gas.
OR
(a) 3.1 g of a gas at 101oC occupies same volume as 0.187 g of Hydrogen gas at 37oC at same pressure. Calculate the molar mass of the gas.
(b) A plot of Pressure (P) vs Volume (V) for a gas at different values of temperature are shown in the figure below.
Which law is shown by the graph? Arrange the temperatures in increasing order.
6. Arrange the following in the increasing order of their property indicated:
(a) Propene, Benzene, Propene (pka values).
(b) Toluene, Chlorobenzene, Nitrobenzene, Phenol (reactivity towards an electrophile)
(c) n-Pentane, ethane, 2-methybutane, 2,2-dimethylpropane (boiling point)
7. At 197oC, equilibrium constant Kc for decomposition of PCl5 is 8 x10-3. If decomposition is depicted as, PCl5 (g) ——— PCl3 (g) + Cl2 (g)
(a) Calculate the value of Kc for the reverse reaction at same temperature.
(b) Calculate the value of Kp for the reaction at same temperature
OR
(a) State La Chatelier’s Principle.
(b) At 500 K, the equilibrium constant Kc for the reaction
N2 (g) +3H2 (g) ——— 2NH3(g) is 0.061
8.(a) What is the structural difference between chlorides of boron and aluminium?
(b) Common oxidation state of Group 14 element is +2 & +4. Which member of Group 14 elements forms stable compound in +2 oxidation state compared to +4 oxidation state. Give reason
OR
(a) Compare the B-F bond length in BF3 and BF4— ion.
(b) Which member of Group 14 element has unique tendency to form p-pie (π) bond? Explain.
(c) Which allotrope of carbon is soluble in benzene?
9. Account for the following:
(a) Halides of boron on hydrolysis produces [B(OH)4]– but halides of Al produces [Al(H2O)6]3+ ion
(b) CO is highly poisonous gas
(c) Gallium has higher ionisation enthalpy than aluminium
8. Carry out the following conversion
(a) Ethyne to Acetophenone
(b) Benzene to parachlorotoluene
(c) Phenol to nitrobenzene
OR
(a) Complete the following sequences of following reaction
(b) Distinguish between propene and propane by a chemical reaction.
11. (a) Alkali metal dissolve in liquid ammonia and form deep blue solution.
What is the change in magnetic nature of the solution when sodium is dissolved in ammonia and allowed to stand for some time?
(b) Arrange the following hydroxides in decreasing order of alkalinity
NaOH, Be(OH)2, KOH, LiOH, CsOH
(c) Explain why Ba imparts colour in flame but Magnesium does not impart any colour.
SECTION – C
12. Read the passage given below and answer the questions that follow
Thermodynamics deals with energy changes in chemical or physical processes an enables to study these changes quantitatively to make useful predictions. The energy stored within a substance is called the internal energy of the system. The change in internal energy (∆U) of a system is the sum of all the energy inputs and outputs to and from the system. Work (W) and heat (Q) are the two modes of internal energyof the system. According to first law of thermodynamics the energy of isolated system is constant and mathematically it is expressed as ∆U = Q + W. Heat exchange at constant pressure for any process gives the measure of enthalpy change (∆H) of the system. Every chemical reaction is associated with change of material as well as energy. The enthalpy change associated with a chemical reaction at 1 bar pressure and 298.15 K is called standard reaction enthalpy (∆rHo). According to Hess’s law, for any chemical reaction the net heat exchange will be same whether the process occurs in one stage or in many stages. According to second law of thermodynamics, in a spontaneous chemical reaction the net entropy of both the system as well as surrounding will increase, i.e., ∆ Stotal> 0. Gibbs free energy is another thermodynamic quantity that helps in predicting the direction of spontaneity of a process. Gibbse free energy is defined as G = H – TS where H = U+PV. For any chemical process at constant pressure and temperature Gibbs free energy of the system decreases, i.e, ∆G < 0. U, H, S and G all are state function and extensive property where as q and w are path function.
(a) Consider the following sublimation process: I2 (solid) à I2 (vapour)
At which condition of temperature the above reaction will be spontaneous?
(b) Although work done by the system is a path function, but when work is carried out Under specific process then it is independent of the path. What is the process when work behaves as a state function?
(c) State the relation between ∆U and ∆H for the given reaction at constant temperature and pressure
(d) 8 gram of oxygen is compressed isothermally and reversibly at a temperature of 27oC from 10L to 5L. Calculate q and w for the process. Oxygen gas is behaving like an ideal gas. Given log 2=0.3, R =2 cal K-1mole-1
OR
Calculate the standard enthalpy of formation of CH3OH(l) from the following data:
CH3OH (l) + 3 /2 O2 (g) → CO2 (g) + 2H2O(l); ΔrH 0 = –726 kJ mol–1
C (graphite) + O2 (g) → CO2 (g); ΔcH 0 = –393 kJ mol–1
H2 (g) + 1/ 2 O2 (g) → H2O(l); Δf H 0 = –286 kJ mol–1