1. Chemical Equations

2. TARGET BOARD At the end of this lesson, you should be able to.. construct balanced chemical equations with state symbols.

3.  An equation represents what occurs in a chemical reaction.  Can be written using words or chemical formulae Word Equation: Sodium + Hydrochloric acid  Sodium chloride + Hydrogen Chemical Equation: 2 Na + 2 HCl  2 NaCl + H 2

4. (s)(aq) (g) Reacting substances, or reactants are on the left-hand side of the equation. Products or substances formed are on the right-hand side of the equation. The arrow means ‘react to form’ The reaction proceeds from left to right. Sodium and hydrochloric acid react to form sodium chloride and hydrogen.

5. Writing the chemical equation Step 1: Write down the chemical formulae of the reactants and products. Step 2: Balance the equation. Step 3: Write down the state symbols.

6. Balancing the equation In a chemical reaction, substances are changed into other substances. No matter is created nor destroyed. i.e. the number of atoms before and after the reaction remains the same.

7. Examination Tip! Marks can be penalized if you give the wrong state symbols, even when the question did not ask for it!

8. Liquid state (l): Pure substance that is in liquid form Aqueous state (aq): Substance dissolved in water Is the substance soluble in water?

9. Many ionic compounds are soluble in water. Most covalent compounds are not soluble in water.

10. SOLUBLE covalent compounds

11. Magnesium reacts with sulphuric acid to form magnesium sulphate and hydrogen.

12. Sulfuric acid reacts with sodium hydroxide to form sodium sulfate and water.

13. SolubleInsoluble All Sodium All Potassium All Ammonium All nitrates Sulphates except Chlorides except Iodides except Bromides except Carbonates except SPA Hydroxides except SPA Oxides except SPA PbSO4 and BaSO4 PbCl 2 and AgCl PbI 2 and AgI PbBr 2 and AgBr