The heat of combustion of ethane, C2H6, is 1560 kJ/mol. What is the heat of combustion of ethane, in kJ per gram?

Question

BlackTom AI · Accepted Answer

Question restatement: The heat of combustion of ethane, C2H6, is 1560 kJ/mol. What is the heat of combustion of ethane, in kJ per gram?

Option analysis:
1) 4.69 × 10^4 kJ/g
This value is extremely large for a per-gram heat of combustion. To get such a figure, one would have to divide by a very small molar mass or misapply units. Since the molar mass of ethane is about 30 g/mol, the correct per-gram value should be on the order of tens of kJ per gram, not tens of thousands. Therefore this option is incorrect.

2) 9.39 × 10^26 kJ/g
This is an astronomical number and clearly unphysical for a chemical thermodynamics quantity per gram. The calculation would require an utterly erroneous conversion factor or exponent. In context, this option is obviously wrong.

3) 51.9 kJ/g
This is of the correct order of magnitude. The heat of combustion per mole is 1560 kJ per 30.068 g (molar mass of C2H6 ≈ 30.07 g/mol). Doing the division 1560 kJ/mol ÷ 30.07 g/mol gives approximately 51.8–51.9 kJ/g. This matches the given choice and aligns with standard unit conversions for heats of combustion.

4) 195 kJ/g
This value is somewhat higher than the calculated 51.8–51.9 kJ/g and suggests a miscalculation, such as dividing by an underestimated molar mass or mixing up units. Since the molar mass is around 30 g/mol, 195 kJ/g would require 1560 kJ per 8 g, which is inconsistent with the actual molar mass of ethane. Hence this option is incorrect.

The heat of combustion of ethane, C2H6, is 1560 kJ/mol. What is the heat of combustion of ethane, in kJ per gram?单项选择题

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