Question

Calculate the enthalpy change of combustion for ethane (C2H6) when 5.00 g of ethane is completely burned in excess oxygen gas, given that the standard enthalpy of combustion of ethane is -1560 kJ/mol.

Answer 1

First, we need to determine the number of moles of ethane  C2H6  in 5.00 g. The molar mass of ethane is:C2H6 =  2  12.01 g/mol for C  +  6  1.01 g/mol for H  = 24.02 + 6.06 = 30.08 g/molNow, we can find the number of moles of ethane:moles of C2H6 =  mass of C2H6  /  molar mass of C2H6 moles of C2H6 = 5.00 g / 30.08 g/mol = 0.166 molesNext, we can use the standard enthalpy of combustion of ethane  -1560 kJ/mol  to calculate the enthalpy change for the combustion of 0.166 moles of ethane:H_combustion = moles of C2H6  standard enthalpy of combustionH_combustion = 0.166 moles  -1560 kJ/mol = -258.96 kJTherefore, the enthalpy change of combustion for 5.00 g of ethane is approximately -259 kJ.