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An engineer wants to determine an efficient method for condensing large amounts of steam into liquid water. Which constant should she use?
A
Hfus
B
–Hvap
C
Hvap
D
–Hfus
22
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Which statement about exothermic reactions is accurate?
A
As reactants form products, the potential energy decreases.B
As reactants form products, the potential energy increases.C
Thermal energy is transferred from the product to the reacting substances.D
Thermal energy is transferred from the surroundings to the reacting substances.23
The enthalpy of formation for C6 H6 (I) is 49.0 kJ/mol. Consider the following reaction.Is the reaction endothermic or exothermic, and what is the enthalpy of reaction? Use .
A
exothermic; Hrxn = 49.0 kJ
B
exothermic; Hrxn = –49.0 kJ
C
endothermic; Hrxn = 49.0 kJ
D
endothermic; Hrxn = –49.0 kJ
24
The molar heat of vaporization for methane, CH4, is 8.53 kJ/mol. How much energy is absorbed when 54.8 g of methane vaporizes at its boiling point?Use .
A
6.42 kJB
29.1 kJC
137 kJD
467 kJ25
What scientific tool would be the most helpful when measuring the temperature of a substance that is undergoing a phase change?
A
a spectrophotometerB
a thermometerC
the periodic tableD
a scaleDid you find these answers helpful?
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