The heat effect of combustion of benzene is 3267.7 kJ. Make a thermochemical equation for

The heat effect of combustion of benzene is 3267.7 kJ. Make a thermochemical equation for the combustion of benzene and calculate: how much heat will be released when burning 18 g of benzene?

Given:
Q = 3267.7 kJ / mol
m (C6H6) = 18 g

To find:
Q1 -?

Decision:
1) Write the equation of the thermochemical reaction:
C6H6 + 7.5O2 => 6CO2 + 3H2O + 3267.7 kJ;
2) Calculate the molar mass of C6H6:
M (C6H6) = Mr (C6H6) = Ar (C) * N (C) + Ar (H) * N (H) = 12 * 6 + 1 * 6 = 78 g / mol;
3) Calculate the amount of substance C6H6:
n (C6H6) = m (C6H6) / M (C6H6) = 18/78 = 0.23 mol;
4) Calculate the amount of heat:
1 mol C6H6 – 3267.7 kJ;
0.23 mol C6H6 – Q1 kJ;
Q1 = 0.23 * 3267.7 / 1 = 751.6 kJ.

Answer: The amount of heat is 751.6 kJ.