Iron weighing 7 grams reacted with chlorine. This formed ferric chloride.

Given:
m (Fe) = 7 g
Q1 = 50 kJ

To find:
thermochemical equation -?

1) Write the reaction equation:
2Fe + 3Cl2 => 2FeCl3 + Q;
2) Calculate the molar mass of Fe:
M (Fe) = Ar (Fe) = 56 g / mol;
3) Calculate the amount of the substance Fe:
n (Fe) = m (Fe) / M (Fe) = 7/56 = 0.125 mol;
4) Draw up the proportion and solve:
0.125 mol Fe – 50 kJ;
2 mol Fe – Q kJ;
Q = 2 * 50 / 0.125 = 800 kJ;
5) Write the equation of the thermochemical reaction:
2Fe + 3Cl2 => 2FeCl3 + 800 kJ.

Answer: 2Fe + 3Cl2 => 2FeCl3 + 800 kJ.