Question

A type of hot pack uses the reaction of finely divided iron metal with oxygen from air to generate heat. Given the thermochemical equation below, how much heat can be released if 45.4 g of iron is consumed? 4 Fe(s)+3 029)2 Fe203(s) AH-1.65 MJ o

a. 1.34 x 103 KJ

b. 336 kJ O

c. 672 kJ

d. 2.68 x 103kJ

e. 41.3 kJ

Answer 1

b. 336 kJ

Step-by-step explanation:

The molar mass of iron is 55.8 g/mol, so the number of moles for 45.4g is:

n = mass/molar mass

n = 45.4/55.8

n = 0.8136 mol

For the reaction given, 4 moles of iron will release 1.65x10³ kJ, so:

4 moles ---------------- 1.65x10³ kJ

0.8136 mol------------ x

By a simple direct three rule:

4x = 1.34x10³

x = 336 kJ