January 2018 NY Regents Chemistry Exam
44 What is the net amount of heat released when two moles of C2H6(g) are formed from its elements at 101.3 kPa and 298 K? (1) 42.0 kJ
(2) 84.0 kJ
(3) 126.0 kJ
(4) 168.0 kJ
Solution: Table I on the Reference Table provides heats of reactions for different reactions.
84 kJ of heat is released for 1 mole of C2H6(g) according to the equation (the coefficient for C2H6 is 1). For 2 moles, we need to multiply the heat by 2.
84kJ*2= 168kJ.
Answer: 4
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