Phase Transitions

Question 1
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Heat of fusion of benzene is 10 J at 0oC, if Cp of solid benzene is 10 J/oC, and that of liquid benzene is 5 J/oC what is the enthalpy change of benzene from – 10oC to 10oC?
160 J
200 J
240 J
300 J
Explanation:
∆H = -10∫010.dT + 10 + 0∫105.dT = 10*10 + 10 + 5*10 = 160 J.
Question 2
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15 J is the latent heat for melting of ice, what is the heat of transition from 0oC ice to 15oC water if heat of transition from 0oC water to 15oC water is 10 J?
10 J
15 J
25 J
40 J
Explanation:
H = 15 + 10 = 25 J.
Question 3
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If Cp of liquid water is 10 J/oC, what is the enthalpy change of water at standard conditions from – 10oC to 0oC?
10 J
50 J
100 J
Cannot be determined
Explanation:
Since the phase of water from – 10oC to 0oC is solid ice, but Cp of liquid water is given, so it cannot be determined.
Question 4
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150 J is the latent heat for vaporization of water, what is the heat of transition from 50oC water to 100oC steam if heat of transition from 50oC water to 100oC water is 12 J?
12 J
152 J
162 J
200 J
Explanation:
H = 150 + 12 = 162 J.
Question 5
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If Cp of liquid benzene is 15 J/oC, what is the enthalpy change of water from 5oC to 10oC?
15 J
50 J
75 J
90 J
Explanation:
∆H = 5∫1015.dT = 75 J.
Question 6
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If Cp of solid benzene is 10 J/oC, what is the enthalpy change of water from 5oC to 75oC?
5 J
10 J
75 J
700 J
Explanation:
∆H = 5∫7510.dT = 700 J.
Question 7
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5 J is the latent heat for melting of ice, what is the heat of transition from 0oC ice to 15oC water if heat of transition from 0oC water to 15oC water is 12 J?
5 J
12 J
15 J
17 J
Explanation:
H = 5 + 12 = 17 J.
Question 8
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What is the latent heat for melting?
Heat of vaporization
Heat of fusion
Heat of Solidification
None of the mentioned
Explanation:
Latent heat for melting is called heat of vaporization.
Question 9
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If Cp of steam is 105 J/oC, what is the enthalpy change of steam from 106oC to 118oC?
420 J
640 J
890 J
1260 J
Explanation:
∆H = 106∫118105.dT = 1260 J.
Question 10
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Which of the following is heat required in phase transitions?
Latent Heat
Sensible Heat
Depends on type of phase transition
None of the mentioned
Explanation:
Heat required for phase transitions is latent heat.