Q. In an isothermal process, which of the following statements is true?
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A.
The temperature remains constant.
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B.
The internal energy changes.
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C.
Work done is zero.
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D.
Heat transfer is zero.
Solution
In an isothermal process, the temperature remains constant, which means the internal energy of an ideal gas does not change.
Correct Answer:
A
— The temperature remains constant.
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Q. What is the change in enthalpy (ΔH) for the reaction: H2(g) + 1/2 O2(g) → H2O(l) if the standard enthalpy of formation of H2O(l) is -285.8 kJ/mol?
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A.
-285.8 kJ/mol
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B.
285.8 kJ/mol
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C.
0 kJ/mol
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D.
571.6 kJ/mol
Solution
The change in enthalpy for the reaction is equal to the standard enthalpy of formation of H2O(l), which is -285.8 kJ/mol.
Correct Answer:
A
— -285.8 kJ/mol
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Q. What is the enthalpy change (ΔH) for the reaction: 2H2(g) + O2(g) → 2H2O(g) if ΔHf for H2O(g) is -241.8 kJ/mol?
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A.
-483.6 kJ
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B.
241.8 kJ
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C.
0 kJ
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D.
483.6 kJ
Solution
The enthalpy change for the reaction is 2 times the standard enthalpy of formation of H2O(g), which is -241.8 kJ/mol, giving -483.6 kJ.
Correct Answer:
A
— -483.6 kJ
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Q. What is the enthalpy change for the reaction: N2(g) + 3H2(g) → 2NH3(g) if the standard enthalpy of formation of NH3(g) is -45.9 kJ/mol?
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A.
-91.8 kJ
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B.
45.9 kJ
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C.
0 kJ
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D.
91.8 kJ
Solution
The enthalpy change for the reaction is 2 times the standard enthalpy of formation of NH3(g), which is -45.9 kJ/mol, giving -91.8 kJ.
Correct Answer:
A
— -91.8 kJ
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Q. What is the standard enthalpy change for the combustion of methane (CH4) if ΔHf for CO2(g) is -393.5 kJ/mol and for H2O(l) is -285.8 kJ/mol?
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A.
-890.3 kJ/mol
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B.
890.3 kJ/mol
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C.
0 kJ/mol
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D.
393.5 kJ/mol
Solution
The standard enthalpy change for the combustion of CH4 is calculated as ΔH = [2(-393.5) + (-285.8)] - [1(0)] = -890.3 kJ/mol.
Correct Answer:
A
— -890.3 kJ/mol
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