Chemical equations

What is the purpose of a chemical equation ?

To represent chemical reactions

Where are the conditions (temperature, etc) required for a reaction (if necessary) placed?

On the arrow

What is a state symbol?

This is a symbol placed after the formula and is used to show the physical state of a reactant and product.

What are the steps in writing a balanced equation?

First, write the equation in words. Then, write the chemical formula for each element and place the state symbol for each element. After that, write down the total number of atoms of each element in the reactants and the products. Lastly, balance the equation by placing coefficients in front of the formulas to alter the proportion of reactants and products.

What are the ionic compounds that are soluble in water?

1. Potassium, sodium and ammonium compounds.

2. Nitrates

3. Ethanoates

4. Hydrogen carbonates

5. Chlorides except silver chloride and lead chloride which is insoluble in cold water but moderately soluble in hot water

6. Sulphates except for lead (ll) sulphate and barium sulphate

What are the ionic compounds that are insoluble in water?

1. Carbonates expect potassium, sodium, and ammonium carbonates.

2. Phosphates except potassium, sodium, and ammonium phosphates.

3. Hydroxides except potassium, sodium, and ammonium hydroxide. Also, calcium hydroxide which is slightly soluble.

4. Metal oxides except potassium, sodium and calcium oxides which react with water to form the equivalent soluble hydroxide.

What are the steps for solving ionic equations?

Firstly, write the balanced equation. Then rewrite it showing any ions that are present in solution ( in solution refers to the aqueous compounds which should be separated) as individual ions. Next, delete any ions in solution that remain unchanged on both sides of the equation. Finally, rewrite the ionic equation showing only the atoms or ions which changed.

What is a spectator ion?

This is an ion that does not take place in the chemical reaction. The are the ions that remain unchanged

What is a chemical reaction?

This is a fundamental process that occurs when two or more substances (reactant) undergo a transformation, resulting in the production of a new substance (product) with different properties or characteristics.

What are the types of chemical reactions?

1. Synthesis reaction

2. Decomposition reaction

3. Single displacement reaction

4. Ionic precipitation or double displacement reaction

5. Neutralisation reaction

6. Oxidation-reduction reaction

7. Reversible reaction

What is a synthesis reaction?

This is a reaction in which two or more substances chemically combine to form one product. Example:

1. H + O 》 H2O

2. C + O2》 CO2

What is a decomposition reaction?

This is a reaction in which a single reactant is broken down into two or more products. Example:

1. 2NaOH (s)》 Na2O(s) + H2O(g)

2. H2CO3(aq) 》CO2(g) + H2O(l)

What is a single displacement reaction?

This is a reaction that occurs between an element in its free state and a compound. Example:

1. Zn (s) + HCl(aq) 》ZnCl2(aq) + H2 (g)

What is an ionic precipitation/double displacement reaction?

This is a reaction that usually involves two compounds in solution (aqueous) where the compounds exchange ions. Example:

1. AgNO3(aq)+KBr(aq)》AgBr(s)+ KNO3(aq)

2. BaCl(aq)+Na2SO4(aq)》BaSO4(s)+2NaCl(aq)

What is neutralisation reaction?

This is a reaction that occurs between a base and acid in which the acid is neutralised by the base and produces a salt and water. Example:

1. NaOH(aq)+HCl》NaCl(aq)+H2 (l)

What is an oxidation reduction/redox reaction?

This is a reaction in which one reactant is oxidised and the other is reduced. Example:

1. CH4(g)+2O2(g)》CO2(g)+2H2O(g)

What is a reversible reaction?

This is a reaction in which the direction of the chemical change can be easily reversed. In other words, the products can react to produce the original reactants again.