In 1774 Joseph Priestly conducted one of his most famous experiments which

lead to a method for the preparation of oxygen. The experiment involved heating
a sample of mercury II oxide with a large lens.

The equation for this reaction is shown below:

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

a) What volume of O2(g) would be obtained if 1.08g of mercury
II oxide were completely decomposed? (Given that 1 mole of a gas occupies 24
dm3 under the experimental conditions)

2 answers

Here is a worked example. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html
According to the laws of thermodynamics, if you heat a large enought object, it gets enough energy it implies. What whould happen if you add 80 joules of energy to 1kg of zinc metal.... i just dont get it