B3 Chemical Reactions, Formulae and Equations

Question 1

In a chemical reaction, how are new substances formed

Answer 1

by the rearrangement of atoms and their electrons, but no nuclei are destroyed or created

Question 2

What are the three steps required in any chemical equation

Answer 2

• Step 1: Write down the chemical formulae of reactants and products
• Step 2: Balance the equation
o Balance elements other than H and O first
• Step 3: Add state symbols
o (s) solid, (l) liquid, (g) gas, (aq) aqueous

Question 3

What are the four steps required in writing ionic equations

Answer 3

• Step 1: Write the balanced chemical equation for the reaction, including state symbols
• Step 2: Rewrite the chemical equation in terms of ions for substances in the aqueous state.
• Step 3: Cancel the spectator ions (ions that do not react and are found on both sides of the equation)
• Step 4: Rewrite the balanced ionic equation without spectator ions (check that there are equal net charges on both sides)