how do you find the heat released from a combustion?


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For the complete combustion of 1.000 mole of methane gas at 298 K and 1 atm pressure, change of heat = -890.4 kJ/mol. What will be the heat released when 1.85 g of methane is combusted underthese conditions?

A.) 7701 kJ

B.) -103 kJ

C.) 103 kJ

D.) -7701 kJ

Please explain

Find the number of moles of methane combusted by dividing the mass of methane by the molar mass (16 g/mol)

Multiply the moles of methane times the molar heat of combustion (-840.4 kJ/mol) to find the heat released. 

Note: the negative sign just indicates that the heat is being released.  Given that fact we can easily eliminate A and C without even doing any calculations.