At constant pressure, the combustion of 5.00 g of C2H6 (g) releases 259 kJ of heat. What is ΔH for the reaction? 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(l)
The heat of combustion is -3120 kJ.
You know that 5.00 g of C₂H₆ releases 259 kJ of heat.
You want to calculate the heat liberated by 2 mol of C₂H₆.
The enthalpy change of combustion for that reaction will be
Start with the given balanced chemical equation
Notice that 2 moles of ethane take part in this reaction.
Now, you were given the heat released when 5.00 g of ethane undergoes combustion. Use ethane's molar mass to determine how many moles of ethane must undergo combustion for that much heat to be released
Because the given reaction requires the combustion of 2 moles of ethane, the amount of heat released will be
Rounded to three sig figs, the number of sig figs given for 5.00 g and 259 kJ, answer will be