What salts and other products form when acids react with metals, oxides, hydroxides and carbonates?
Reactions of acids: the general reactions of acids with metals, metal oxides, metal hydroxides and metal carbonates, the salts produced, and the tests for hydrogen and carbon dioxide.
A focused answer to Edexcel GCSE Chemistry topic 3, covering the general reactions of acids with metals, metal oxides, metal hydroxides and metal carbonates, the salts each acid produces, writing balanced and ionic equations, and the chemical tests for hydrogen and carbon dioxide.
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What this dot point is asking
Edexcel wants you to recall the general reactions of acids with metals, metal oxides, metal hydroxides and metal carbonates, name the salt each acid produces, write balanced and ionic equations, and describe the chemical tests for hydrogen and carbon dioxide. These reactions feed directly into preparing salts.
The salts each acid makes
The name of the salt comes from the acid used. The metal part comes from the metal, oxide, hydroxide or carbonate.
So magnesium plus sulfuric acid gives magnesium sulfate, and zinc plus hydrochloric acid gives zinc chloride.
Acid plus metal
A reactive metal reacts with an acid to give a salt and hydrogen:
For example, . The reaction fizzes as hydrogen is given off, and more reactive metals react faster: magnesium fizzes vigorously, zinc reacts steadily and iron only slowly. Unreactive metals such as copper, silver and gold do not react with dilute acids at all, because they are below hydrogen in the reactivity series.
This reaction is a redox reaction: the metal atoms lose electrons to form metal ions (oxidation) and the hydrogen ions gain electrons to form hydrogen molecules (reduction). For magnesium with hydrochloric acid the ionic equation is , with the chloride ions acting as spectator ions. The speed of fizzing is a quick way to compare the reactivity of two metals, and the hotter the reaction mixture becomes, the more exothermic and reactive the reaction.
Acid plus metal oxide or hydroxide (neutralisation)
Metal oxides and metal hydroxides are bases. They react with acids to give a salt and water only, with no gas. This is neutralisation:
For example, and . The ionic equation is always for an acid and an alkali.
Acid plus metal carbonate
A metal carbonate reacts with an acid to give a salt, water and carbon dioxide:
For example, . The fizzing is the carbon dioxide being released.
Testing the gases
Worked equations
Try this
Q1. Name the salt made when sodium hydroxide reacts with hydrochloric acid. [1 mark]
- Cue. Sodium chloride.
Q2. Write the word equation for an acid reacting with a metal carbonate. [2 marks]
- Cue. Acid plus metal carbonate gives salt plus water plus carbon dioxide.
Q3. Describe the test for carbon dioxide and the positive result. [2 marks]
- Cue. Bubble the gas through limewater; it turns cloudy (milky).
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20184 marksMagnesium reacts with dilute sulfuric acid. Name the two products, write the balanced symbol equation, and describe the test that confirms the gas produced.Show worked answer →
A 4-mark reaction-and-test question.
The products are magnesium sulfate and hydrogen (1 mark). The balanced equation is (1 mark). To test the gas, collect it and hold a lighted splint at the mouth of the tube (1 mark): hydrogen burns with a squeaky pop (1 mark).
Markers reward naming the correct salt for sulfuric acid (a sulfate) and the squeaky-pop test for hydrogen.
Edexcel 20224 marksCalcium carbonate reacts with dilute hydrochloric acid. Write the balanced symbol equation, name the gas produced, and describe the test that confirms it. State symbols are not required.Show worked answer →
A 4-mark carbonate-reaction question.
The equation is (1 mark, with the ). The gas produced is carbon dioxide (1 mark). To test it, bubble the gas through limewater (calcium hydroxide solution) (1 mark): the limewater turns cloudy (milky) (1 mark).
Markers reward the three carbonate products (salt, water and carbon dioxide) and the limewater test.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Chemistry (1CH0) specification — Pearson Edexcel (2016)