Neutralisation (OCR GCSE Chemistry A (Gateway)): Revision Note
Reactions of Acids with Metal Oxides & Hydroxides
Metal oxides and metal hydroxides act as bases
Bases have pH values above 7
Many bases are insoluble in water but the ones that do dissolve in water are called alkalis
Examples of alkalis are soluble metal hydroxides such as NaOH and Ca(OH)2
When bases react with acids, a neutralisation reaction occurs
In all acid-base neutralisation reactions, salt and water are produced:
acid + base ⟶ salt + water
This neutralisation reaction can be generalised to the H+ ions (from the acid) reacting with the OH– ions (from the base) to produce water
The overall ionic equation for this is:
H+ + OH– ⟶ H2O
The identity of the salt produced depends on the acid used and the positive ions in the base
Hydrochloric acid produces chlorides, sulfuric acid produces sulfate salts and nitric acid produces nitrates
Acids and Metals Oxides or Hydroxides Summary Table

The following are some specific examples of reactions between acids and metal oxides / hydroxides:
2HCl + CuO ⟶ CuCl2 + H2O
H2SO4 + 2NaOH ⟶ Na2SO4 + 2H2O
HNO3 + KOH ⟶ KNO3 + H2O
Reactions of Acids with Metal Carbonates & Metals
Acids & Metal carbonates
Acids will react with metal carbonates to form the corresponding metal salt, carbon dioxide and water
These reactions are easily distinguishable from acid – metal oxide/hydroxide reactions due to the presence of effervescence caused by the carbon dioxide gas:
acid + metal carbonate ⟶ salt + water + carbon dioxide
Acids & Metal Carbonates Reactions Table

The following are some specific examples of reactions between acids and metal carbonates:
2HCl + Na2CO3 ⟶ 2NaCl + H2O + CO2
H2SO4 + CaCO3⟶ CaSO4 + H2O + CO2
Acids & Metals
Only metals above hydrogen in the reactivity series will react with dilute acids.
The more reactive the metal then the more vigorous the reaction will be.
Metals that are placed high on the reactivity series such as potassium and sodium are very dangerous and react explosively with acids.
When acids react with metals they form a salt and hydrogen gas:
The general equation is:
metal + acid ⟶ salt + hydrogen
Acid-Metal Reactions Table

The following are some specific examples of reactions between acids and metals:

Examiner Tips and Tricks
Not all reactions of acids are neutralisations. For example when a metal reacts with an acid, although a salt is produced there is no water formed so it does not fit the definition of neutralisation.
Naming Salts
The name of a salt has two parts
The first part comes from the metal, metal oxide, metal hydroxide or metal carbonate used in the reaction
The second part comes from the acid
The name of the salt can be determined by looking at the reactants
For example hydrochloric acid always produces salts that end in chloride and contain the chloride ion, Cl–
Other examples:
Sodium hydroxide reacts with hydrochloric acid to produce sodium chloride
Zinc oxide reacts with sulfuric acid to produce zinc sulfate
You need to be able to predict all the products based on the reactants used, not just the salt
For example:
magnesium carbonate + nitric acid ⟶ magnesium nitrate + carbon dioxide + water
copper oxide + sulfuric acid ⟶ copper sulfate + water
sodium + hydrochloric acid ⟶ sodium chloride + hydrogen
Worked Example
Name the products formed when:
Calcium carbonate reacts with dilute hydrochloric acid
Sodium hydroxide reacts with dilute sulfuric acid
Magnesium reacts with dilute nitric acid
Answer:
Calcium chloride, water and carbon dioxide
Sodium sulfate and water
Magnesium nitrate and hydrogen
Worked Example
Write the balanced symbol equation for the reaction between zinc and sulfuric acid (H2SO4)
Answer:
Zinc and sulfuric acid react to produce the salt, zinc sulfate and hydrogen gas
The balanced equation is therefore:
Zn + H2SO4 ⟶ ZnSO4 + H2
Examiner Tips and Tricks
Make sure you learn the chemical formula of the three main acids you will be asked about: nitric acid (HNO3), hydrochloric acid (HCl), and sulfuric acid (H2SO4).
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