Please solve for H Refer to Table 1 (on the left) for the four alkanes: methane,

Question

Please solve for H

Refer to Table 1 (on the left) for the four alkanes: methane, propane, butane, and octane to answer the following questions. How are their compositions similar? They all have the same formula, but the atoms are bonded together differently in each molecule. They are all composed of carbon and hydrogen. How does the amount of heat released (in kJ/mol) upon combustion vary with molar mass? The amount of heat released decreases as molar mass increases. The amount of heat released increases as molar mass increases. Explain why their heats of combustion are dramatically different in terms of kJ/mol but nearly the same in terms of kJ/g? Essay answers are limited to about 500 words (3800 characters maximum, including spaces).

Explanation / Answer

Heat of combustion for fuels

Part F : Their composition similarity,

they are all composed of carbon and hydrogen

Part G : Among of heat released vary with molar mass,

The amount of heat released increases as molar mass increases

Part H : Their heat of combustion are dramatically different in terms of kJ/mol but nearly the same in terms of kJ/g

Heat of combustion is different in terms of kJ/mol because all the fuels burn at different rates in terms of number of moles reacting with oxygen. Whereas, in terms of kJ/g, fuel weight balances out due to molar masses, so a higher molar mass with higher heat of combustion would end up having similar value than a lower molar mass fuel with lower heat of combustion.

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