Given the equation si(s) + 2cl2(g) → sicl2(g) ? sicl2(l) + 687 kj, how much heat is produced when 106 g of cl2 react?

No of moles of Cl2 = mass of Cl2 / molar mass of Cl2
                                = 106g / (35.4*2)g/mol
                                = 106g /  70.9 g/mol = 1.495 moles
the heat produced = no of moles of Cl2 * ΔHrxn/2mol Cl2
when we have ΔHrxn from the equation = + 687 KJ so, 
by substitution:
                                = 1.495 mol * 687 KJ/2 mol Cl2
                                = 513.5 KJ