Neutralisation Reactions (T4)

Question 1

What happens when an acid reacts with a metal hydroxide? Give the word equation and what you would observe in the reaction.

Answer 1

When an acid reacts with a metal hydroxide, the only products formed are salt plus water.

acid + metal hydroxide > a salt + water

You would observe:

• a temperature rise
• the pH of the reaction mixture changing

Question 2

What happens when a metal oxide reacts with an acid? Give the word equation and what you would observe.

Answer 2

When an acid reacts with a metal oxide, the only products formed are salt plus water.

acid + metal oxide > a salt + water

You would observe:

• a temperature rise
• the pH of the reaction mixture changing

Question 3

What happens when an acid reacts with a metal carbonate? Give the word equation and observations.

Answer 3

When an acid reacts with a metal carbonate, the products formed are a salt plus water and also carbon dioxide is formed.

acid + metal carbonate > a salt + water + carbon dioxide

You usually observe bubble of gas being given off during the reaction. You can show that the gas is carbon dioxide by bubbling it through limewater - it turns cloudy when it reacts with carbon dioxide.

Question 4

What is a neutralisation?

Answer 4

• the chemical reaction that occurs when you mix together an acid and a base
• a neutral solution is made when you mix just the right amount of acid and base together

Question 5

Give three examples for the use of neutralisation..

Answer 5

• farmers use lime (calcium oxide) to neutralise acid soils
• your stomachs contains hydrochloric acid and too much causes indigestion. Antacid tablets contains bases like magnesium hydroxide and magnesium carbonate to neutralise the extra acid
• bee stings are acidic. They can be neutralised using baking powder which contains sodium hydrogen carbonate

Question 6

The reaction of acid and alkali can sometimes be so sensitive that mildly acidic reactions, like the binding of carbon dioxide into water, can cause changes in a mild alkali.

Using the change of calcium hydroxide in water as an example, explain what happens and give the word and chemical equations…

Answer 6

Calcium hydroxide + carbon dioxide > calcium carbonate + water

Ca(OH)2 + CO2 > CaCo3 + H2O

• the reaction is visible from the water going cloudy
• the salt formed takes the carbon from the gas and produces water, while forming a salt from the hydroxide
• carbon dioxide gas dissolves to form carbonic acid
• calcium carbonate precipitates out
• calcium carbonate reacts with carbonic acid to form calcium hydrogencarbonate, which is more soluble, so the precipitate dissolves

Question 7

What are the word and chemical equations for the neutralisation of hydrogen and hydroxide?

Answer 7

Hydrogen (aq) + hydroxide (aq) > water (l)

H+(aq) + OH-(aq) > H2O(l)

Question 8

Neutralisation can be used to make..

Answer 8

Salts