SHE 1325
DEPARTMENT OF CHEMISTRY, CFS, IIUM
SEMESTER II, 2013/2014
QUIZ 2
NAME:……………………………………………MATRIC
NO………………..GROUP:………
Answer all questions.
[30 mins]
PART I [5 marks]
1
Which of the following statement is correct about an endothermic reaction?
A
The temperature of the surroundings increases
B
The reaction releases heat into the surroundings
C
The enthalpy change for the reaction is negative
D
The enthalpy of the products is higher than that of the reactants
D/L1/f
1
Which of the following statement is incorrect about an endothermic
reaction?
A
The temperature of the surroundings decreases
B
The reaction releases heat into the surroundings
C
The enthalpy change for the reaction is positive
D
The enthalpy of the products is lower than that of the reactants
B/L1/f
1
Which of the following statement is correct about an exothermic reaction?
A
The temperature of the surroundings decreases
B
The reaction absorbs heat from the surroundings
C
The enthalpy change for the reaction is negative
D
The enthalpy of the products is higher than that of the reactants
C/L1/f
2
Which of the following statement is not correct about an open system?
A
Exchanges matter with its surroundings
B
Exchanges energy with its surroundings
C
Exchanges both matter and energy with its surroundings
D
Exchanges neither matter nor energy with its surroundings
D/L1/
2
Which of the following statement is correct about a closed system?
A
Exchanges matter with its surroundings
B
Exchanges energy with its surroundings
C
Exchanges both matter and energy with its surroundings
D
Exchanges neither matter nor energy with its surroundings
B/L1/
2
Which of the following statement is correct about an isolated system?
A
Exchanges matter with its surroundings
B
Exchanges energy with its surroundings
C
Exchanges both matter and energy with its surroundings
D
Exchanges neither matter nor energy with its surroundings
D/L1/
3
What is the ∆H° for the following reaction?
C2H6(g) +
7
2
O2(g)  2CO2(g) + 3H2O(g)
[∆H°f (C2H6) = -84.7 kJ/mol ; ∆H° f (CO2) = -393.5 kJ/mol, ∆H° f
(H2O) = -241.8 kJ/mol]
A
C
3
550.6 kJ
-1427.7 kJ
B
D
-720 kJ
-1597.1 kJ
C/L2/m
What is the ∆H°f CuO(s) for the following reaction?
Cu2O(s) + 1/2 O2(g)  2 CuO(s)
∆H° rxn = -146 kJ
[∆H°f (Cu2O(s)) = -168.6 kJ/mol]
A
C
3
22.6
-157.3
B
D
-22.6
-314.6
C/L2/m
What is the ∆H°f (Cu2O(s)) for the following reaction?
Cu2O(s) + 1/2 O2(g)  2 CuO(s)
∆H° rxn = -146 kJ
[∆H°f CuO(s)? =-157.3 kJ/mol]
A
C
4
B
D
168.6
-303.3
C/L2/m
0.522 g sample of octane (C8H18) is burned in a bomb calorimeter that has a
heat capacity of 8.151 kJ K-1. The temperature increases 10 °C. What is the
heat of combustion for octane?
A
C
4
11.3
-168.6
-81.51 kJ
- 1.78 x 104 kJ
B
D
- 42.55 kJ
-9.31 x 103 kJ
C/L2/h(i)
0.522 g sample of hexane(C6H14) is burned in a bomb calorimeter that has a
heat capacity of 7.60 kJ K-1. The temperature increases 10 °C. What is the
heat of combustion for hexane?
A
-39.67 kJ
B
-76kJ
C
4
5
5
D
-1.2 x 104 kJ
D/L2/h(i)
1.50 g sample of butane (C4H10) is burned in a bomb calorimeter that has a
heat capacity of 5.50 kJ K-1. The temperature increases 8 °C. What is the
heat of combustion for butane?
A
C
5
-145.6 kJ
-29.3 kJ
-66 kJ
B
D
-44 kJ
- 1.71 x 103 kJ
D/L2/h(i)
Which of the following halide is expected to have higher lattice energy than
KBr?
I
II
III
IV
Lithium chloride
Sodium fluoride
Cessium chloride
Rubidium fluoride
A
C
I and II
III and IV
B
D
II and III
I and IV
A/L3/p
Which of the following halide is expected to have lower lattice energy than
KBr?
I
II
III
IV
Lithium chloride
Sodium fluoride
Cessium chloride
Rubidium fluoride
A
C
I and II
II and IV
B
D
II and III
III and IV
D/L3/p
Which of the following halide is expected to have higher lattice energy than
NaBr?
I
II
III
IV
Pottasium bromide
Lithium chloride
Magnesium chloride
Cessium bromide
A
C
I and II
III and IV
B
D
II and III
II and IV
B/L3/p
PART II [10 MARKS]
Set 1
1
Write two state functions mentioned in the statement below.
[2]
Nitric oxide reacts with chlorine to form NOCl. ∆Ho for this reaction is 10.56 kJ at 298 K.
2 NO (g) + Cl2 (g)  2 NOCl (g)
Temperature/298 K [1];
∆Ho/-10.56 kJ [1]
2
L1/(c)
Define enthalpy change of neutralization.
[1]
The enthalpy change when 1 mole of H+ reacts with 1 mole of OH- to
produce 1 mole of H2O at standard states.
L1/d
3
The Born-Haber diagram for the formation of potassium chloride, KCl(s), is
shown below.
[Note: The numerical values of the enthalpy changes involved are given
without the signs –ve or +ve.]
Enthalpy
K+(g) + Cl(g)
Step 2 = 349 kJ
121 kJ
K+(g) + ½ Cl2(g)
K+(g) + Cl– (g)
418 kJ
K(g) + ½ Cl2(g)
715.5 kj
Step I =89.5 kJ
K(s) + ½ Cl2(g)
∆H°f KCl
KCl(g)
(i)
(ii)
Name of the enthalpy that occurred in Step I and Step II.
Step I:
Atomization enthalpy of K(g)
[1]
Step II:
Electron affinity of Cl(g)
[1]
Calculate the ∆H°f KCl(s).
[2]
L2/o
[2]
∆H°f KCl(s) + (715.5) = +89.5 + 418 + 121 +(- 349) [1]
∆H°f KCl(s) = -436 kJ/mol
[1]*must have unit!!
L2/0
4
Calculate ∆H for the reaction below using energy cycle,
Ca(s) + ½O2(g) + CO2(g)  CaCO3(s)
Given,
Ca(s) + ½O2(g)  CaO(s)
CaCO3(s)  CaO(s) + CO2(g)
Ca(s) + ½O2(g) + CO2(g)
+½O2(g)
-635.1 kJ
∆H=?
∆H= -635.1 kJ
∆H= -178.3 kJ
∆H=?
CaCO3(s)
178.3
+ CO2(g)
CaO(s)
∆H = -635.1 kJ + 178.3 kJ
= -456.8 kJ
L3/m
Set II
1
Write two state functions mentioned in the statement below.
[2]
Carbon is burnt with oxygen at 298K. Enthalpy release from this
burning is -3267 kj/mol.
C(g) + O2(g)  CO2(g)
Temperature/298 K ;
∆Ho/-3267 kJ
2
L1/(c)
Define enthalpy change of hydration.
[1]
The enthalpy change when 1 mole of a gaseous ion ishydrated
at standard states
3
L1/i
The Born-Haber diagram for the formation of potassium chloride, KCl(s), is
shown below.
[Note: The numerical values of the enthalpy changes involved are given
Enthalpy
K+(g) + Cl(g)
349 kJ
Step II = 121 kJ
K+(g) + ½ Cl2(g)
K+(g) + Cl– (g)
Step I = 418 kJ
K(g) + ½ Cl2(g)
- Lattice
enthalpy
89.5 kJ
K(s) + ½ Cl2(g)
436 kJ
KCl(g)
without the signs –ve or +ve.]
(i)
Name of the enthalpy that occurred in Step I and Step II.
[2]
(ii)
Step I:
Ist ionization enthalpy of K(g)
[1]
Step II:
Atomization enthalpy of Cl2(g)
[1]
Calculate the lattice enthalpy of KCl(s).
[2]
LE + (–436) = +89.5 + 418 + 121 +(- 349)
LE = 715.5 kJ/mol
L2/o
[1]
[1]*must have unit!!
L2/o
4
Calculate ∆H for the reaction below using energy cycle,
2NOCl(g)  N2(g) + O2(g) + Cl2(g) ∆H=?
Given,
½N2(g) + ½O2(g)  NO(g)
NO(g) + ½Cl2(g)  NOCl(g)
∆H= -90.3 kJ
∆H= -38.6 kJ
- ∆H=?
2NOCl(g)
N2(g) + O2(g) + Cl2(g)
∆H= -90.3 x 2 kJ
∆H= -38.6 x 2 kJ
+Cl2(g)
+ O2(g)
2NO(g)
- ∆H = (-90.3)2 + (-38.6) 2
= 257.8 kJ
L3/m
[3]
Set III
1
Write two state functions mentioned in the statement below.
[2]
Carbon monoxide reacts with oxygen gas to form carbon dioxide.
Enthalpy release from the reaction is -566kJ. Pressure of the system
decrease to 0.7 atm.
2CO(g) + O2(g)  2CO2(g)
Pressure/0.7 atm;
∆Ho /-566kJ
1
L1/(c)
Define standard enthalpy change of solution.
[1]
The enthalpy change when 1 mole of solid ionic compound
dissolves into its aqueous ions at standard states.
L1/l
3
The Born-Haber diagram for the formation of calcium fluoride, CaF2(s), is
shown below.
[Note: The numerical values of the enthalpy changes involved are given
without the signs –ve or +ve.]
Enthalpy
Ca2+(g) + 2F(g)
159 kJ x 2
Step 2 = 328 kJ x 2
Ca2+(g) + F2(g)
Ca2+(g) + 2F– (g)
1150 kJ
Ca+(g) + F2(g)
590 kJ
Ca(g) + F2(g)
Ca(s) + F2(g)
LE
178 kJ
Step 1 = 1220 kJ
CaF2(g)
(i)
(ii)
Name of the enthalpy that occurred in Step I and Step II.
Step I:
Enthalpy of formation of K(g)
[1]
Step II:
Electron affinity of F(g)
[1]
Calculate the lattice enthalpy of CaF2(s).
[2]
L2/o
[2]
LE + (–1220) = +178 +590+ 1150 +(159x2) +(-328x2)
[1]
LE = 2800 kJ/mol
[1]*must have unit!!
L2/o
4
Calculate ∆H for the reaction below using energy cycle,
C(s) + ½O2(g)  CO(g)
∆H=?
Given,
C(s) + O2(g)  CO2(g)
2CO(g) + O2(g)  2CO2(g)
∆H= -393.5 kJ
∆H= -566.0 kJ
[3]
-393.5
C(s) + O2(g)
CO2(g)
+O2(g)
∆H=?
+ ½ O2(g)
−
CO(g)
[2]
𝟓𝟔𝟔
𝟐
∆H =-393.5+(566/2)
∆H = -110.5 kJ [1]
L3/m