What are the products when a metal reacts with a dilute acid?

The products are a salt and hydrogen gas. The general equation is: metal + acid → salt + hydrogen.

Why can copper not react with dilute hydrochloric acid?

Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from an acid. Only metals above hydrogen in the reactivity series react with dilute acids.

Hydrochloric acid reacts with metals to produce ________ salts, while sulfuric acid produces ________ salts.

Hydrochloric acid produces chloride salts (e.g. MgCl 2 ), while sulfuric acid produces sulfate salts (e.g. MgSO 4 ). Note: the salt ends in -ide or -ate, not the element name ("chloride" not "chlorine").

True or False? Magnesium reacts more vigorously with dilute hydrochloric acid than zinc does.

True. Magnesium is more reactive than zinc and sits higher in the reactivity series. The more reactive the metal, the more vigorous the reaction, producing faster effervescence.

Write the balanced symbol equation for magnesium reacting with hydrochloric acid.

The products are magnesium chloride and hydrogen gas: Mg (s) + 2HCl (aq) → MgCl 2 (aq) + H 2 (g)

Only metals ________ hydrogen in the reactivity series react with dilute acids. Potassium and sodium react ________ with acids and must not be used in experiments.

Only metals above hydrogen in the reactivity series react with dilute acids. Potassium and sodium react explosively with acids and must not be used in experiments.

Why are reactions between metals and dilute acids described as redox reactions?

Metal-acid reactions are redox reactions because oxidation and reduction occur simultaneously: the metal atoms lose electrons (oxidation) and the hydrogen ions gain electrons (reduction).

Write the ionic equation for zinc reacting with hydrochloric acid and identify the spectator ions.

Ionic equation: Zn + 2H⁺ → Zn²⁺ + H 2 The Cl⁻ ions are spectator ions as they appear unchanged on both sides of the full equation and are missing from the ionic equation.

In the reaction between zinc and hydrochloric acid, zinc atoms are ________ because they ________ electrons to form Zn 2+ ions.

Zinc atoms are oxidised because they lose electrons to form Zn 2+ ions. The oxidation half equation is: Zn → Zn 2+ + 2e -

True or False? In the reaction between magnesium and hydrochloric acid, hydrogen gas is the species that is reduced.

False. H + ions are reduced, not hydrogen gas: 2H + + 2e - → H 2 The H⁺ ions gain electrons. Students must identify the specific ion, not just write "hydrogen."

For the reaction Mg (s) + H 2 SO 4 (aq) → MgSO 4 (aq) + H 2 (g), write the ionic equation and identify the spectator ion.

Ionic equation: Mg + 2H + → Mg 2+ + H2. The SO 4 2- ion is the spectator ion as it is unchanged in the reaction and is removed when writing the ionic equation.

Write the two half equations for magnesium reacting with sulfuric acid: Oxidation: Mg → ____ + ____ Reduction: ____ + 2e - → H 2

Oxidation: Mg → Mg 2+ + 2e - (magnesium atoms lose 2 electrons and are oxidised). Reduction: 2H + + 2e - → H 2 (hydrogen ions gain electrons and are reduced).

What is produced in all acid-base neutralisation reactions?

All acid-base neutralisation reactions produce a salt and water . General equation: acid + base → salt + water If the base is a metal carbonate, carbon dioxide is also produced. General equation: acid + base → salt + water + CO 2

Which salts do hydrochloric acid, sulfuric acid, and nitric acid produce?

Hydrochloric acid produces chloride salts. Sulfuric acid produces sulfate salts. Nitric acid produces nitrate salts. The metal or metal ion gives the first part of the salt name.

When an acid reacts with a metal carbonate, the three products are a ________ , ________ and ________ .

When an acid reacts with a metal carbonate, the three products are a salt , water and carbon dioxide . For example: 2HCl + Na 2 CO 3 → 2NaCl + H 2 O + CO 2

True or False? If an acid-base reaction produces effervescence (fizzing), the base must be a metal carbonate.

True. Effervescence indicates carbon dioxide is being produced, which only occurs when the base is a metal carbonate . Metal oxides and metal hydroxides react with acids without producing a gas.

Name the salt produced when copper oxide reacts with sulfuric acid, and write the equation.

The salt produced is copper sulfate . The first part of the salt name (copper) comes from the base; the second part (sulfate) comes from the acid. The equation is: CuO + H 2 SO 4 → CuSO 4 + H 2 O

The first part comes from the ________ (or ________ ) used; the second part comes from the ________ .

The first part comes from the metal (or base ) used; the second part comes from the acid . For example: potassium hydroxide + nitric acid → potassium nitrate

What is the difference between a base and an alkali?

A base is any substance that neutralises an acid. An alkali is a base that dissolves in water to form an alkaline solution. All alkalis are bases, but not all bases are alkalis. For example, copper oxide is a base but not an alkali; sodium hydroxide is both.

Why is the insoluble solid added in excess when preparing a soluble salt?

The solid is added in excess to ensure all of the acid reacts . Any unreacted acid would become dangerously concentrated during evaporation. Note: "so it fully reacts" gains no marks because "it" refers to the solid, not the acid.

Write the equation for the preparation of copper(II) sulfate from copper(II) oxide and dilute sulfuric acid.

Sulfuric acid must be used (not hydrochloric acid) to produce a sulfate salt. CuO (s) + H 2 SO 4 (aq) → CuSO 4 (aq) + H 2 O (l)

After reacting an insoluble solid in excess with acid, the next steps are: ________ to remove excess solid Gently ________ until small crystals appear Leave to ________ slowly.

After reacting an insoluble solid in excess with acid, the next steps are: Filter to remove excess solid Gently heat until small crystals appear Leave to crystallise slowly. "Heat to dryness" is not accepted by mark schemes.

True or False? The correct final step for obtaining solid salt crystals from solution is to "heat to dryness."

False. The solution should be heated gently (partially evaporated) until small crystals begin to appear, then left to cool and crystallise . Mark schemes explicitly reject "heat to dryness" as it destroys the crystal structure.

When filtering the excess solid from an acid-salt solution, what must you state to gain the mark?

You must state that filtration removes the excess (unreacted) solid. Simply writing "filter the mixture" without explaining what is being removed is insufficient.

Larger salt crystals form if the filtered solution is left to ________ over several ________ , rather than being heated quickly. Slow evaporation allows crystals more time to grow.

Larger crystals form if the filtered solution is left to evaporate over several days , rather than being heated quickly. Slow evaporation allows crystals more time to grow.

How do you check if a salt solution is saturated during the preparation of a soluble salt?

Dip a cold glass rod into the hot solution. If crystals form on the end of the rod, the solution is saturated and ready to be left to crystallise.

State three observations when excess copper carbonate is added to warm dilute sulfuric acid.

Fizzing/effervescence (CO 2 produced) The green solid dissolves and the solution turns blue "Colour change" alone is too vague: specify what changed colour. Fizzing stops and solid remains at the bottom.

In the preparation of copper sulfate, the correct sequence is: Warm the acid → add excess ________ → ________ to remove excess → heat until ________ → leave to crystallise.

In the preparation of copper sulfate, the correct sequence is: Warm the acid → add excess copper oxide/carbonate → filter to remove excess → heat until saturated (crystals form on cold glass rod) → leave to crystallise.

True or False? You can tell that the base is in excess because solid remains at the bottom of the beaker after stirring.

True. Mark schemes require students to state that "solid remains" as evidence the base is in excess. This confirms all the acid has been used up and the reaction is complete.

A student describes the control variable in a salt preparation investigation as "the amount of acid." Why is this incorrect?

"Amount" is too vague and is rejected by mark schemes. Students must write the "volume of acid" (in cm 3 ).

Copper(II) sulfate crystals are ________ in colour and have a ________ (geometric) shape, reflecting the repeating ionic lattice structure.

Copper(II) sulfate crystals are blue in colour and have a regular (geometric) shape, reflecting the repeating ionic lattice structure.

Which ions are present in acid solutions and which in alkaline solutions?

Acid solutions contain H + (hydrogen) ions . Alkaline solutions contain OH - (hydroxide) ions . The pH scale measures the concentration of H + ions in solution.

What are the pH ranges for strong acids, weak acids, neutral solutions, weak alkalis, and strong alkalis?

Strong acid: pH 1–3 Weak acid: pH 4–6; Neutral: pH 7 Weak alkali: pH 8–11 Strong alkali: pH 12–14

Universal indicator gives only an ________ pH value; it is not suitable for titrations because it lacks a ________ colour change. A sharp colour change is needed to identify the ________ .

Universal indicator gives only an approximate pH value; it is not suitable for titrations because it lacks a sharp colour change. A sharp colour change is needed to identify the end-point .

True or False? Adding nitric acid to water causes the pH to decrease and universal indicator to change from green to red.

True. Adding acid increases the H⁺ ion concentration, which decreases the pH. Universal indicator changes from green (neutral) to red/orange (acidic). Confusing "more acidic" with "higher pH" is a common exam mistake.

Write the ionic equation for all acid-alkali neutralisation reactions.

H⁺ (aq) + OH⁻ (aq) → H 2 O (l) State symbols are expected. This applies to all acid-alkali neutralisations. Writing "acid + alkali → salt" is a common mistake that gains zero marks as it does not show ion transfer.

When HCl dissolves in water, it produces ________ ions in water, making the solution acidic. When NaOH dissolves in water, it produces ________ ions in water, making the solution alkaline.

When HCl dissolves in water, it produces H + (hydrogen) ions in water, making the solution acidic. When NaOH dissolves in water, it produces OH - (hydroxide) ions in water, making the solution alkaline.

Why is the reaction between magnesium and hydrochloric acid not classified as a neutralisation reaction?

Neutralisation requires H⁺ and OH⁻ ions to react to form water (H⁺ + OH⁻ → H 2 O). When magnesium reacts with HCl, no OH⁻ ions are present and no water is formed; only a salt and hydrogen gas are produced.

A strong acid completely ionises in aqueous solution , releasing all its hydrogen ions. Examples include hydrochloric acid (HCl), nitric acid (HNO 3 ), and sulfuric acid (H 2 SO 4 ).

What is the difference between a strong acid and a weak acid, and why does acid strength not mean the same as concentration?

A strong acid completely ionises in aqueous solution; a weak acid only partially ionises, establishing an equilibrium. Concentration describes how many moles of acid are dissolved: a concentrated weak acid can have a higher pH than a dilute strong acid.

The pH scale is logarithmic: each pH unit represents a factor of ________ change in hydrogen ion concentration. A solution at pH 2 has ________ times more H⁺ ions than a solution at pH 4.

The pH scale is logarithmic: each pH unit represents a factor of 10 change in hydrogen ion concentration. A solution at pH 2 has 100 times more H⁺ ions than a solution at pH 4.

True or False? A concentrated solution of ethanoic acid always has a lower pH than a dilute solution of hydrochloric acid.

False. Ethanoic acid is a weak acid and only partially ionises, so even at high concentration it produces fewer H⁺ ions than dilute HCl, which completely ionises.

Why can a dilute solution of hydrochloric acid have a lower pH than a concentrated solution of ethanoic acid?

HCl is a strong acid and completely ionises, so all its molecules release H⁺ ions. Ethanoic acid is a weak acid and only partially ionises, producing far fewer H⁺ ions even at higher concentration.

In a weak acid solution, the equilibrium for ionisation lies to the , meaning most molecules remain and only a small proportion of H⁺ ions are released.

In a weak acid solution, the equilibrium for ionisation lies to the left , meaning most molecules remain intact and only a small proportion of H⁺ ions are released.

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Reactions of Acids (AQA GCSE Combined Science: Trilogy: Chemistry): Flashcards

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What are the products when a metal reacts with a dilute acid?

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What are the products when a metal reacts with a dilute acid?
The products are a salt and hydrogen gas. The general equation is:
metal + acid → salt + hydrogen.
Why can copper not react with dilute hydrochloric acid?
Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from an acid. Only metals above hydrogen in the reactivity series react with dilute acids.
Hydrochloric acid reacts with metals to produce ________ salts, while sulfuric acid produces ________ salts.
Hydrochloric acid produces chloride salts (e.g. MgCl₂), while sulfuric acid produces sulfate salts (e.g. MgSO₄).
Note: the salt ends in -ide or -ate, not the element name ("chloride" not "chlorine").
True or False?
Magnesium reacts more vigorously with dilute hydrochloric acid than zinc does.
True.
Magnesium is more reactive than zinc and sits higher in the reactivity series. The more reactive the metal, the more vigorous the reaction, producing faster effervescence.
Write the balanced symbol equation for magnesium reacting with hydrochloric acid.
The products are magnesium chloride and hydrogen gas:
Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)
Only metals ________ hydrogen in the reactivity series react with dilute acids. Potassium and sodium react ________ with acids and must not be used in experiments.
Only metals above hydrogen in the reactivity series react with dilute acids. Potassium and sodium react explosively with acids and must not be used in experiments.
Why are reactions between metals and dilute acids described as redox reactions?
Metal-acid reactions are redox reactions because oxidation and reduction occur simultaneously: the metal atoms lose electrons (oxidation) and the hydrogen ions gain electrons (reduction).
Write the ionic equation for zinc reacting with hydrochloric acid and identify the spectator ions.
Ionic equation:
Zn + 2H⁺ → Zn²⁺ + H₂
The Cl⁻ ions are spectator ions as they appear unchanged on both sides of the full equation and are missing from the ionic equation.
In the reaction between zinc and hydrochloric acid, zinc atoms are ________ because they ________ electrons to form Zn²⁺ ions.
Zinc atoms are oxidised because they lose electrons to form Zn²⁺ ions. The oxidation half equation is:
Zn → Zn²⁺ + 2e^-
True or False?
In the reaction between magnesium and hydrochloric acid, hydrogen gas is the species that is reduced.
False.
H⁺ ions are reduced, not hydrogen gas:
2H⁺ + 2e^- → H₂
The H⁺ ions gain electrons. Students must identify the specific ion, not just write "hydrogen."
For the reaction Mg (s) + H₂SO₄ (aq) → MgSO₄ (aq) + H₂ (g), write the ionic equation and identify the spectator ion.
Ionic equation: Mg + 2H⁺ → Mg²⁺ + H2.
The SO₄^2- ion is the spectator ion as it is unchanged in the reaction and is removed when writing the ionic equation.
Write the two half equations for magnesium reacting with sulfuric acid:
Oxidation: Mg → ____ + ____
Reduction: ____ + 2e^- → H₂
Oxidation: Mg → Mg²⁺ + 2e^- (magnesium atoms lose 2 electrons and are oxidised).
Reduction: 2H⁺+ 2e^- → H₂ (hydrogen ions gain electrons and are reduced).
What is produced in all acid-base neutralisation reactions?
All acid-base neutralisation reactions produce a salt and water. General equation:
acid + base → salt + water
If the base is a metal carbonate, carbon dioxide is also produced. General equation:
acid + base → salt + water + CO₂
Which salts do hydrochloric acid, sulfuric acid, and nitric acid produce?
Hydrochloric acid produces chloride salts.
Sulfuric acid produces sulfate salts.
Nitric acid produces nitrate salts.
The metal or metal ion gives the first part of the salt name.
When an acid reacts with a metal carbonate, the three products are a ________, ________ and ________.
When an acid reacts with a metal carbonate, the three products are a salt, water and carbon dioxide.
For example: 2HCl + Na₂CO₃ → 2NaCl + H₂O + CO₂
True or False?
If an acid-base reaction produces effervescence (fizzing), the base must be a metal carbonate.
True.
Effervescence indicates carbon dioxide is being produced, which only occurs when the base is a metal carbonate. Metal oxides and metal hydroxides react with acids without producing a gas.
Name the salt produced when copper oxide reacts with sulfuric acid, and write the equation.
The salt produced is copper sulfate. The first part of the salt name (copper) comes from the base; the second part (sulfate) comes from the acid.
The equation is: CuO + H₂SO₄ → CuSO₄ + H₂O
The first part comes from the ________ (or ________) used; the second part comes from the ________.
The first part comes from the metal (or base) used; the second part comes from the acid.
For example: potassium hydroxide + nitric acid → potassium nitrate
What is the difference between a base and an alkali?
A base is any substance that neutralises an acid.
An alkali is a base that dissolves in water to form an alkaline solution.
All alkalis are bases, but not all bases are alkalis. For example, copper oxide is a base but not an alkali; sodium hydroxide is both.
Why is the insoluble solid added in excess when preparing a soluble salt?
The solid is added in excess to ensure all of the acid reacts. Any unreacted acid would become dangerously concentrated during evaporation. Note: "so it fully reacts" gains no marks because "it" refers to the solid, not the acid.
Write the equation for the preparation of copper(II) sulfate from copper(II) oxide and dilute sulfuric acid.
Sulfuric acid must be used (not hydrochloric acid) to produce a sulfate salt.
CuO (s) + H₂SO₄ (aq) → CuSO₄ (aq) + H₂O (l)
After reacting an insoluble solid in excess with acid, the next steps are:
- ________ to remove excess solid
- Gently ________ until small crystals appear
- Leave to ________ slowly.
After reacting an insoluble solid in excess with acid, the next steps are:
- Filter to remove excess solid
- Gently heat until small crystals appear
- Leave to crystallise slowly.
"Heat to dryness" is not accepted by mark schemes.
True or False?
The correct final step for obtaining solid salt crystals from solution is to "heat to dryness."
False.
The solution should be heated gently (partially evaporated) until small crystals begin to appear, then left to cool and crystallise. Mark schemes explicitly reject "heat to dryness" as it destroys the crystal structure.
When filtering the excess solid from an acid-salt solution, what must you state to gain the mark?
You must state that filtration removes the excess (unreacted) solid.
Simply writing "filter the mixture" without explaining what is being removed is insufficient.
Larger salt crystals form if the filtered solution is left to ________ over several ________, rather than being heated quickly. Slow evaporation allows crystals more time to grow.
Larger crystals form if the filtered solution is left to evaporate over several days, rather than being heated quickly. Slow evaporation allows crystals more time to grow.
How do you check if a salt solution is saturated during the preparation of a soluble salt?
Dip a cold glass rod into the hot solution. If crystals form on the end of the rod, the solution is saturated and ready to be left to crystallise.
State three observations when excess copper carbonate is added to warm dilute sulfuric acid.
1. Fizzing/effervescence (CO₂ produced)
2. The green solid dissolves and the solution turns blue
  "Colour change" alone is too vague: specify what changed colour.
3. Fizzing stops and solid remains at the bottom.
In the preparation of copper sulfate, the correct sequence is:
- Warm the acid
- → add excess ________
- → ________ to remove excess
- → heat until ________
- → leave to crystallise.
In the preparation of copper sulfate, the correct sequence is:
- Warm the acid
- → add excess copper oxide/carbonate
- → filter to remove excess
- → heat until saturated (crystals form on cold glass rod)
- → leave to crystallise.
True or False?
You can tell that the base is in excess because solid remains at the bottom of the beaker after stirring.
True.
Mark schemes require students to state that "solid remains" as evidence the base is in excess. This confirms all the acid has been used up and the reaction is complete.
A student describes the control variable in a salt preparation investigation as "the amount of acid." Why is this incorrect?
"Amount" is too vague and is rejected by mark schemes. Students must write the "volume of acid" (in cm³).
Copper(II) sulfate crystals are ________ in colour and have a ________ (geometric) shape, reflecting the repeating ionic lattice structure.
Copper(II) sulfate crystals are blue in colour and have a regular (geometric) shape, reflecting the repeating ionic lattice structure.
Which ions are present in acid solutions and which in alkaline solutions?
Acid solutions contain H⁺ (hydrogen) ions.
Alkaline solutions contain OH^- (hydroxide) ions.
The pH scale measures the concentration of H⁺ ions in solution.
What are the pH ranges for strong acids, weak acids, neutral solutions, weak alkalis, and strong alkalis?
Strong acid: pH 1–3
Weak acid: pH 4–6;
Neutral: pH 7
Weak alkali: pH 8–11
Strong alkali: pH 12–14
Universal indicator gives only an ________ pH value; it is not suitable for titrations because it lacks a ________ colour change. A sharp colour change is needed to identify the ________.
Universal indicator gives only an approximate pH value; it is not suitable for titrations because it lacks a sharp colour change. A sharp colour change is needed to identify the end-point.
True or False?
Adding nitric acid to water causes the pH to decrease and universal indicator to change from green to red.
True.
Adding acid increases the H⁺ ion concentration, which decreases the pH. Universal indicator changes from green (neutral) to red/orange (acidic).
Confusing "more acidic" with "higher pH" is a common exam mistake.
Write the ionic equation for all acid-alkali neutralisation reactions.
H⁺ (aq) + OH⁻ (aq) → H₂O (l)
State symbols are expected. This applies to all acid-alkali neutralisations.
Writing "acid + alkali → salt" is a common mistake that gains zero marks as it does not show ion transfer.
When HCl dissolves in water, it produces ________ ions in water, making the solution acidic.
When NaOH dissolves in water, it produces ________ ions in water, making the solution alkaline.
When HCl dissolves in water, it produces H⁺ (hydrogen) ions in water, making the solution acidic.
When NaOH dissolves in water, it produces OH^- (hydroxide) ions in water, making the solution alkaline.
Why is the reaction between magnesium and hydrochloric acid not classified as a neutralisation reaction?
Neutralisation requires H⁺ and OH⁻ ions to react to form water (H⁺ + OH⁻ → H₂O).
When magnesium reacts with HCl, no OH⁻ ions are present and no water is formed; only a salt and hydrogen gas are produced.
Define strong acid.
A strong acid completely ionises in aqueous solution, releasing all its hydrogen ions.
Examples include hydrochloric acid (HCl), nitric acid (HNO₃), and sulfuric acid (H₂SO₄).
What is the difference between a strong acid and a weak acid, and why does acid strength not mean the same as concentration?
A strong acid completely ionises in aqueous solution; a weak acid only partially ionises, establishing an equilibrium.
Concentration describes how many moles of acid are dissolved: a concentrated weak acid can have a higher pH than a dilute strong acid.
The pH scale is logarithmic: each pH unit represents a factor of ________ change in hydrogen ion concentration.
A solution at pH 2 has ________ times more H⁺ ions than a solution at pH 4.
The pH scale is logarithmic: each pH unit represents a factor of 10 change in hydrogen ion concentration.
A solution at pH 2 has 100 times more H⁺ ions than a solution at pH 4.
True or False?
A concentrated solution of ethanoic acid always has a lower pH than a dilute solution of hydrochloric acid.
False.
Ethanoic acid is a weak acid and only partially ionises, so even at high concentration it produces fewer H⁺ ions than dilute HCl, which completely ionises.
Why can a dilute solution of hydrochloric acid have a lower pH than a concentrated solution of ethanoic acid?
HCl is a strong acid and completely ionises, so all its molecules release H⁺ ions. Ethanoic acid is a weak acid and only partially ionises, producing far fewer H⁺ ions even at higher concentration.
In a weak acid solution, the equilibrium for ionisation lies to the , meaning most molecules remain and only a small proportion of H⁺ ions are released.
In a weak acid solution, the equilibrium for ionisation lies to the left, meaning most molecules remain intact and only a small proportion of H⁺ ions are released.

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