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This reaction is: a spontaneous at all temperatures b spontaneous only at high temperature c spontaneous only at low temperature d nonspontaneous at all temperatures Question 12 Choose t

Question 1

Use the information provided to calculate the

standard enthalpy of formation (kJ·mol–1) of

acetylene, C2H2(g):

C2H2(g) + 5/2O2(g)  2CO2(g) + H2O(l)

∆H˚ = –1299.5 kJ

C(s) + O2(g)  CO2(g) ∆H˚ = –393.5 kJ

H2(g) + 1/2O2(g)  H2O(l) ∆H˚ = –285.8 kJ

a) –1978.8

b) –1121.4

c) 226.7

d) 453.4

Question 2

Which statement is always true for a spontaneous

reaction?

a) The entropy change for the system is

negative

b) The enthalpy change for the system is

negative

c) The entropy change for the universe is

positive

d) The free energy change for the system is

positive

Question 3

Arrange the following reactions in order of

increasing ∆S value (All substances are in gaseous

state):

N2 + O2 = 2NO (1)

2CH4 = C2H2 + 2H2 (2)

2SO2 + O2 = 2SO3 (3)

b) 2,1,3

d) 2,3,1

Question 4

Which of the following reactions, in the same

conditions, have the largest and the smallest value of

∆S:

N2(g) + O2(g) = 2NO(g) (1)

KClO4 (s) = KCl (s) + 2O2 (g) (2)

C2H2 (g) + 2H2 (g) = C2H6 (g) (3)

a) 1, 2

b) 2, 3

c) 2, 1

d) 3, 1

Question 5

Arrange the following substances (1 mole of each) in

order of increasing the value of entropy at 25°C and

1 atm: (I) Ne(g), (II) SO2(g), (III) Na(s), (IV)

NaCl(s), (V) H2(g)

a) (I)<(II)< (V)<(III)<(IV) b) (III)<(IV)< (I)<(II)< (V) c) (III)<(IV)< (I)<(V)< (II) d) (IV)<(III)< (I)<(V)< (II)

Question 6

Which statement is correct at 25˚C and 1 atm pressure?

a) ∆G˚f for Hg(l) = 0 kJ.mol–1

b) ∆H˚f for I2(g) = 0 kJ.mol–1

c) ∆H˚f for H2O(l) = 0 kJ.mol–1

d) S˚ for O2(g) = 0 J.mol–1.K–1

Question 7

The enthalpy of fusion for NaF(s) at its melting point (992˚C) is 29.3 kJ.mol-1 What is the value of ∆S˚fus in J.mol-1.K-1?

a) 43.2 b) 33.9 c) 29.5 d) 23.2

Question 8

Choose the correct answer for the reversible reaction

in certain conditions having ∆Go>0 a) The equilibrium constant of the reaction is smaller than 1

b) The equilibrium constant of the reaction is greater than 1

c) The reaction in those conditions is reactant-favored

d) (a) and (c) are correct

Question 9

For a reaction at constant pressure to be spontaneous, which relationship must be correct?

a) ∆Hrxn < 0 b) ∆Grxn < 0 c) ∆Srxn < 0 d) ∆Suniv < 0

Question 10

Calculate ∆Go

298 of the following reaction:

2A(g) + B(g) C(g)

f (kJ/mol) So(J/mol.K)

A (g)

B (g) C( g)

191 70.8 -197

244 300 164 a) – 160.15 kJ

b) + 956 kJ c) – 463, 85kJ d) Another answer

Question 11

For the following reaction,

C2H6 (g) → C2H4 (g) + H2 (g)

∆H0= +137KJ/mol, ∆S0= +120J/(mol.K) This

reaction is:

a) spontaneous at all temperatures

b) spontaneous only at high temperature

c) spontaneous only at low temperature

d) nonspontaneous at all temperatures

Question 12

Choose the correct answer.

The transition of water from the liquid to the gaseous

state at 110oC:

a) ∆G>0, ∆H<0, and ∆S=0

b) ∆G<0, ∆H>0, and ∆S>0

c) ∆G<0, ∆H>0, and ∆S<0

d) ∆G>0, ∆H>0, and ∆S>0

Question 13

At the certain conditions, Kc=200 for the following

reaction:

concentrations were detected in a mixture Which

direction must the reaction proceed for equilibrium to

be established? CA=CB=10-3M, Cc=0.01M

a) The system transfers in reverse direction

b) The system transfers in forward direction

c) The system is at the equilibrium state

d) Unable to predict the state of the reaction

Question 14

Consider the reaction carried out at constant volume:

2SO2(g) + O2(g)  2SO3(g)

For initial concentrations of SO2 and O2 of 2.0 M and

1.5 M, respectively After the equilibrium state is

established, the O2 concentration is 0.80 M What is

the value of Kc for this reaction?

a) 6.8

b) 2.9

c) 0.34

d) 0.15

Question 15

The ∆G°298 the following reaction is 2.60 J/mol

H2(g) + I2(g) ⇌ 2HI(g)

When the partial pressures of H2(g), I2(g), HI(g) are

4.26 atm, 0.024 atm, and 0.23 atm, respectively

Calculate ∆G of above reaction at 25oC

a) -1629.9 kJ/mol;

b) -1.63 kJ/mol;

c) +0.97 kJ/mol;

d) +0.97 kJ/mol;

Question 16

The gaseous compound NOBr decomposes according

to the following equation at 350 K, the equilibrium

constant, Kp, is 0.15 What is the value of ∆G˚?

NOBr(g)  NO(g) + 1/2 Br2(g) a) –5.5 × 103 J/mol b) –2.4 × 103 J/mol c) 2.4 × 103 J/mol d) 5.5 × 103 J/mol

Question 17

A 2.0 L container is charged with a mixture of 6.0 moles of CO(g) and 6.0 moles of H2O(g) and the following reaction takes place: When equilibrium is reached the [CO2] = 2.4 M What is the value of Kc

for the reaction?

CO(g) + H2O(g)  CO2(g) + H2(g) a) 16

b) 4.0 c) 0.25 d) 0.063

Question 18

For the synthesis of ammonia, Kc is 1.2 at 375 ˚C

N2(g) + 3 H2(g)  2 NH3(g), What is Kp at this temperature?

a) 4.1 × 10–8 b) 4.2 × 10–4 c) 1.3 × 10–3 d) 3.4 × 103

Question 19

The equilibrium system, N2O4(g)  2NO2(g), has Kp

= 11 For which equilibrium system is Kp = 0.091? a) 2NO2(g)  N2O4(g)

b) NO2(g)  1/2 N2O4(g) c) 2N2O4(g)  4NO2(g) d) 1/2 N2O4(g)  NO2(g)

Question 20

The following exothermic reaction is at equilibrium:

2 A(g) + B(g) ⇌ 4D (g)

What is condition for product favored?

1) Increase the temperature 2) Add more D

3) Decrease the volume of the bottle 4) Decrease the temperature

5) Add more A 6) Increase the volume of the bottle

Question 21

Choose the correct expression :

Consider the equilibrium : 2NO2(g) = N2O4(g)

∆Ηo

298= -14kcal In four following statements, the

color (brown) of NO2 will be darkest when:

a) Heating to 373K

b) Cooling to 273K

c) Increase pressure

d) Keep at 298K

Question 22

The reaction A(g) ⇌B(g) + C(g) at 300oC has

Kp=11.5; at 500oC has Kp=33 What is condition for

product-favored?

a) Heating

b) Cooling

c) Compreesing

d) (a) and (c)

Question 23

Choose the correct answer

Consider the system at equilibrium:

NH4HS(s)  NH3(g) + H2S(g) ∆H > 0

Factors which favor the formation of more H2S(g)

include which of the following?

I - adding a small amount of NH4HS(s) at constant

volume

II - increasing the pressure at constant temperature

III -increasing the temperature at constant pressure

a) I only

b) III only

c) I and II only

d) I and III only

Question 24

Molarity is defined as the

a) moles solute/moles solvent

b) moles solute/kg solution

c) moles solute/liters solution

d) moles solute/kg solvent

Question 25

As the concentration of a solute in a

solution increases, the boiling point of the

solution and the vapor pressure of

the solution _

a) increases, increases

b) increases, decreases

c) decreases, increases

d) decreases, decreases

Question 26

Choose the correct answer.

A solution with a concentration higher than the

solubility is

a) unsaturated

b) supercritical

c) saturated

d) supersaturated

Question 27

Pressure has an appreciable effect on the solubility of in liquids

a) gases b) solids c) liquids d) solids and liquids

Question 28

Calculate the freezing point of a 0.055 m aqueous solution of glucose The molal freezing-point-depression constant Kf of water is 1.86 oC/m

a) 0.0286 b) 0.1023 c) -0.0562 d) -0.1023

Question 29

What is the molality of a solution made by

a) 0.0533 b) 0.200 c) 0.360 d) 3.12

Question 30

What is the molality of a solution made by

a) 0.0533 b) 0.200 c) 0.360 d) 3.12

Question 31

A 200g solvent containing A (g) glucose (molecular

weight M) K f is the molal freezing-point-depression

constant of the solven Which expression is true about ∆Tb:

a) ∆Tb = 5 K f.(A/M)

b) ∆Tb = K f.(A/M)

c) ∆Tb = 1/5 K f.(A/M)

d) ∆Tb = K f.A

Question 32

Calculate the vapor-pressure lowering of water when 5.67 g of glucose, C6H12O6, is dissolved in 25.2 g of water at 25 oC The vapor pressure of water at 25 oC is 23.8 mmHg

a) 23.276 mmHg b) 0.7497 mmHg c) 33.32 mmHg

d) 0.524 mmHg

Question 33

Dissolving 5g of each following compounds into

500g of water: C6H12O6, C12H22O11 and C3H5(OH)3

Arrange the following solutions in order of

increasing boiling point (all of those compound are

non-vaporized)

a) C12H22O11 < C6H12O6 < C3H5(OH)3

b) Cannot be arranged

c) C3H5(OH)3 < C6H12O6 < C12H22O11

d) C12H22O11 < C3H5(OH)3 < C6H12O6

Question 34

A 5.1 g sample of CaCl2 is dissolved in a beaker of

water Which of the following statements is true of

this solution?

a) The solution will freeze at a lower temperature

than pure water

b) The solution has a higher vapor pressure than pure water

c) The solution will boil at a lower temperature than pure water

d) Water is the solute in this solution

Question 35 Choose the correct statement about the coefficient k

in the following equation: ∆T = k×Cm (Cm: molality) a) k is a constant depends on the concentration of solute, temperature and the nature of solvent b) k is a constant depends on temperature and the nature of solvent

c) k is a constant only depends on the nature of solvent

d) k is a constant depends on the nature of both solute and solvent