Neutralisation (OCR Gateway GCSE Chemistry)

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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 OHions (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

Acids & Metal Oxides or Hydroxides Summary Table, downloadable IGCSE & GCSE Chemistry revision notes

  • 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

Acid & Metal Carbonate Reactions Table, downloadable IGCSE & GCSE Chemistry revision notes

  • 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

Acids and Metals Summary Table, downloadable IGCSE & GCSE Chemistry revision notes

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

Acids and Metals Examples Table, downloadable IGCSE & GCSE Chemistry revision notes

Examiner Tip

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:

  1. Calcium carbonate reacts with dilute hydrochloric acid
  2. Sodium hydroxide reacts with dilute sulfuric acid 
  3. Magnesium reacts with dilute nitric acid 

Answer:

    1. Calcium chloride, water and carbon dioxide 
    2. Sodium sulfate and water 
    3. 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 Tip

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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Alexandra

Author: Alexandra

Expertise: Chemistry

Alex studied Biochemistry at Newcastle University before embarking upon a career in teaching. With nearly 10 years of teaching experience, Alex has had several roles including Chemistry/Science Teacher, Head of Science and Examiner for AQA and Edexcel. Alex’s passion for creating engaging content that enables students to succeed in exams drove her to pursue a career outside of the classroom at SME.