# Heat in Reactions

[show your work and note what formulas you used]

A mercury mirror forms inside a test tube by the thermal decomposition of mercury(II) oxide.

2 HgO(s) 2 Hg(l) + O2(g)

Hrxn = 181.6 kJ

1. How much heat is needed to decompose 505 g of the oxide?

2. If 270. kJ of heat is absorbed, how many grams of mercury form?

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#### Solution Preview

Stoichiometry Problem

A mercury mirror forms inside a test tube by the thermal decomposition of mercury(II) oxide.

2 HgO(s) ----> 2 Hg(l) + O2(g)

deltaHrxn = 181.6 kJ

1. How much heat is needed to decompose 505 g of the oxide?

We determine the molar mass of HgO. By looking up the masses in the Periodic Table, we find that HgO ...

#### Solution Summary

This Solution contains calculations to aid you in understanding the Solution to these questions.

$2.19