Question

The reaction
Fe + Br2 ---> FeBr2 Delta H = -249.8kJ

Calculate delta H when 10.0 g of FeBr2 is formed.

Answer 1

What's the molar mass FeBr2. That's about 55.85 + 79.9 + 79.9 = approx 216 but you need a more accurate answer. Now you know this. 216 g FeBr2 are formed when 249.8 kJ of energy are released. You only have 10.0 g. Use common sense to tell you how much 10.0 g will release. That's -249.8 kJ x (10/216) = ?

Answer 2

Ahh, that makes a lot of sense. Thanks.