CHM201: Physical Chemistry Ii TMA2 Question an Answer

Question 1 : Calculate the standard entropy change for the following reaction, 2Ag2O(s)→4Ag(s)+O2(g)2Ag2O(s)→4Ag(s)+O2(g); given So[Ag2O]So[Ag2O] = 121.3 J/K·mol, SoSo[Ag(s)] = 42.6 J/K·mol, and So[O2(g)]So[O2(g)] = 205.1 J/K·mol.
A. -126.4 J/K
B. +126.4 J/K
C. +132.9 J/K
D. -205.1 J/K

Answer to question 1 is D. -205.1 J/K

Question 2 : All of the following processes lead to an increase in entropy EXCEPT
A. forming mixtures from pure substances.
B. freezing a liquid.
C. increasing the temperature of a gas.
D. evaporating a liquid.

 

Answer to question 2 B. freezing a liquid.

Question 3 : Of the following product-favoured processes, which are endothermic? 1. the combustion of methane to produce water and carbon dioxide. 2. the expansion of an ideal gas. 3. the melting of ice at temperatures greater than 0ºC.
A. 2 and 3
B. 3 only
C. 2 only
D. 1 only

Answer to question 3 B. 3 only
Question 4 : Predict the signs of ΔHΔH and ΔSΔS for the evaporation of water at 35 ^oC.
A. ΔH<0ΔH<0 and ΔS<0ΔS<0
B. ΔH>0ΔH>0 and ΔS>0ΔS>0
C. ΔH<0ΔH<0 and ΔS>0ΔS>0
D. ΔH>0ΔH>0 and ΔS<0ΔS<0

Answer to question 4 B. ΔH>0ΔH>0 and ΔS>0ΔS>0
Question 5 : Every type of chemical bond contains a certain amount of energy. The total bond energy, which is essentially equivalent to the total potential energy of the system, is a quantity known as:
A. enthalpy.
B. entropy.
C. free energy.
D. kinetic energy.

Answer to question 5 A. enthalpy.
Question 6 : For the following system at equilibrium, what will cause the partial pressure of HF to increase? UO2(s)+4HF(g)→UF4(g)+2H2O(g)UO2(s)+4HF(g)→UF4(g)+2H2O(g)
A. decreasing the pressure
B. adding UO2UO2(s)
C. removing H2O(g)H2O(g)
D. adding UF4(g)UF4(g)

Answer to question 6 is D. adding UF4(g)UF4(g)

Question 7 : In a reaction in which the rate of the reverse reaction is equal to the rate of the forward reaction, a state of ____________ is attained.
A. total entropy
B. thermodynamics
C. product reversibility
D. dynamic equilibrium

Answer to question 7 is D. dynamic equilibrium

Question 8 : A beaker with a mixture of ice and water is maintained at equilibrium: H2O(s)+heat→H2O(l)H2O(s)+heat→H2O(l); If the temperature of the system is decreased:
A. Ice melts to form liquid water (shift to the right)
B. Water freezes to form ice (shifts to the left)
C. The container cacks
D. No change occurs

Answer to question 8 is D. No change occurs

Question 9 : Which reaction is likely to have a negative change in entropy?
A. N2O4(g)→2NO2(g)N2O4(g)→2NO2(g)
B. CaO(s)+CO2(g)�??CaCO3(s)CaO(s)+CO2(g)�??CaCO3(s)
C. 2NH3(s)→N2(g)+3H2(g)2NH3(s)→N2(g)+3H2(g)
D. NaCl(s)→Na+(aq)+Cl−(aq)NaCl(s)→Na+(aq)+Cl−(aq)

Answer to question 9 is B. CaO(s)+CO2(g)�??CaCO3(s)CaO(s)+CO2(g)�??CaCO3(s)
Question 10 : Rate of reaction is defined as the
A. Rate of change of concentration Of either reactant or product per unit time
B. None of the above
C. Rate of change of conc. of product only
D. Rate of change of conc. of reactant only

Answer to question 10 is A. Rate of change of concentration Of either reactant or product per unit time
Question 11 : When extra NH3NH3 is added to the following system at equilibrium: 3H2(g)+N2(g)→2NH3(g)3H2(g)+N2(g)→2NH3(g), what happens?
A. Concentration of hydrogen decreases, but that of hydrogen increases
B. In order to restore equilibrium, the reaction shifts right, toward product
C.  In order to restore equilibrium, the reaction shifts left, toward reactants
D. No change occurs

Answer to question 11 is B. In order to restore equilibrium, the reaction shifts right, toward product
Question 12 : All of the following statements concerning entropy are true EXCEPT
A. entropy is zero for elements under standard conditions.
B. entropy is a state function.
C. a positive change in entropy denotes a change toward greater disorder.
D. entropy values are greater than or equal to zero.

Answer to question 12 is A. entropy is zero for elements under standard conditions

Question 13 : The rate of chemical reaction
A. Decreases as the reaction proceeds
B. Remains constant as reaction proceeds
C. Increases as the reaction proceeds
D. Both (a) and (b)

Answer to question 13 A. Decreases as the reaction proceeds

Question 14 : A reaction with a negative value of ΔGΔG is said to be
A. At equilibrium
B. Reversible
C. Non-spontaneous
D. Spontaneous

Answer to question 14 B. Reversible

Question 15 : In general, the rate of a reaction can be increased by all the factors except
A. Increasing the activation energy
B. Using a catalyst
C. Increasing the concentration of reactants
D. Increasing the temperature

Answer to question 15 is A. Increasing the activation energy

Question 16 : Equilibrium is a state of dynamic molecular behaviour, meaning that
A. reactants turn into products and products turn into reactants at equal rates
B. the reaction eventually comes to a stop.
C. products continually turn into reactants at a progressively faster rate.
D. reactants turn into products and products turn into reactants at different rates.

Answer to question 16 is A. reactants turn into products and products turn into reactants at equal rates

Question 17 : If a process is exothermic and not spontaneous, then what must be true?
A. ΔS<0ΔS<0
B. ΔG=0ΔG=0
C. ΔS>0ΔS>0
D. ΔH>0ΔH>0

Answer to question 17 is D. ΔH>0ΔH>0

Question 18 : The factor that affects the rate of reaction is
A. All of these
B. Temperature of the reactants
C. Catalyst
D. Nature and concentration of the reactants

Answer to question 18 is A. All of these

Question 19 : The reaction below is exothermic: 2SO2(g)+O2(g)→2SO3(g)2SO2(g)+O2(g)→2SO3(g). Le Chatelier’s Principle predicts that __________ will result in an increase in the number of moles of SO3SO3 (g) in the reaction container.
A. increasing the pressure
B. removing some oxygen
C. decreasing the pressure
D. increasing the volume of the container

Answer to question 19 is C. decreasing the pressure

Question 20 : The term �?? dx/dt in the rate expression refers to the
A. Average rate of the reaction
B. instantaneous rate of the reaction
C. Change in concentration of the reactants with time
D. increase in concentration of the reactants

Answer to question 19 is B. instantaneous rate of the reaction