0.7 Representing chemical change  (Page 5/6)

This simulation allows you to practice balancing simple equations.

Balancing simple chemical equations

Balance the following equations:

1. Hydrogen fuel cells are extremely important in the development of alternative energy sources. Many of these cells work by reacting hydrogen and oxygen gases together to form water, a reaction which also produces electricity. Balance the following equation: ${{H}}_2\left(\mathrm{g}\right)+{{O}}_2\left(\mathrm{g}\right)\to \mathrm{H}{}_2\mathrm{O}\left(\mathrm{l}\right)$
2. The synthesis of ammonia ( $\mathrm{NH}{}_3$ ), made famous by the German chemist Fritz Haber in the early 20th century, is one of the most important reactions in the chemical industry. Balance the following equation used to produce ammonia: ${{N}}_2\left(\mathrm{g}\right)+{{H}}_2\left(\mathrm{g}\right)\to \mathrm{NH}{}_3\left(\mathrm{g}\right)$
3. ${Mg}+{{P}}_4\to \mathrm{Mg}{}_3{\mathrm{P}}_2$
4. ${Ca}+{{H}}_2\mathrm{O}\to \mathrm{Ca(OH)}{}_2+\mathrm{H}{}_2$
5. ${{CuCO}}_3+{{H}}_2{\mathrm{SO}}_4\to \mathrm{CuSO}{}_4+{{H}}_2\mathrm{O}+{{CO}}_2$
6. ${{CaCl}}_2+{{Na}}_2{\mathrm{CO}}_3\to \mathrm{CaCO}{}_3+{NaCl}$
7. ${\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}+{{O}}_2\to \mathrm{H}{}_2\mathrm{O}+{{CO}}_2$
8. Barium chloride reacts with sulphuric acid to produce barium sulphate and hydrochloric acid.
9. Ethane ( ${\mathrm{C}}_2{\mathrm{H}}_6$ ) reacts with oxygen to form carbon dioxide and steam.
10. Ammonium carbonate is often used as a smelling salt. Balance the following reaction for the decomposition of ammonium carbonate: $\left({\mathrm{NH}}_4\right){}_2{\mathrm{CO}}_3\left(\mathrm{s}\right)\to {\mathrm{NH}}_3\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+\mathrm{H}{}_2\mathrm{O}\left(\mathrm{l}\right)$

State symbols and other information

The state (phase) of the compounds can be expressed in the chemical equation. This is done by placing the correct label on the right hand side of the formula. There are only four labels that can be used:

1. (g) for gaseous compounds
2. (l) for liquids
3. (s) for solid compounds
4. (aq) for an aqueous (water) solution

Occasionally, a catalyst is added to the reaction. A catalyst is a substance that speeds up the reaction without undergoing any change to itself. In a chemical equation, this is shown by using the symbol of the catalyst above the arrow in the equation.

To show that heat is needed for a reaction, a Greek delta ( $\Delta$ ) is placed above the arrow in the same way as the catalyst.