Acids and alkalis, pH and salts C5
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- Created on: 15-08-22 16:08
General equation:
metal + water
metal + water
metal + water → metal hydroxide + hydrogen
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All metals above ______ in the reactivity series will react with acids producing bubbles of _______ gas
All metals above HYDROGEN in the reactivity series will react with acids producing bubbles of HYDROGEN gas
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Reactions of acid and metals are _____ reactions
Reactions of acid and metals are REDOX reactions
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What can acids be neutralised by?
Bases (eg alkalis and metal oxides) and metal carbonates
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General equation:
acid + base
acid + base
acid + base → salt + water
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General equation:
acid + metal carbonate
acid + metal carbonate
acid + metal carbonate → salt + carbon dioxide + water
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What is an alkali?
A soluble hydroxide base
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What ions do acids produce in aqueous solutions?
(what ions do they release in water)
(what ions do they release in water)
Hydrogen ions (H⁺)
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What ions do alkalis produce in aqueous solutions?
(what ions do they release in water)
(what ions do they release in water)
Hydroxide ions (OH⁻)
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Why is water produced in neutralisation reactions between an acid and an alkali?
What is the equation for the reaction?
What is the equation for the reaction?
Hydrogen ions react with hydroxide ions to produce water
H⁺ (aq) + OH⁻ (aq) → H₂O (l)
H⁺ (aq) + OH⁻ (aq) → H₂O (l)
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What does the particular salt produced in any reaction between an acid and a base/alkali depend on?
• the acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates)
• the positive ions in the base, alkali or carbonate.
• the positive ions in the base, alkali or carbonate.
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What is a strong acid?
Give three examples
Give three examples
A strong acid is completely ionised (splits) in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.
Strong acid reactions are not reversible
Strong acid reactions are not reversible
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What is a weak acid?
Give three examples
Give three examples
A weak acid is only partially ionised (partially splits) in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids.
Weak acid reactions are reversible
Weak acid reactions are reversible
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Strong acids have a ______ pH than weak acids for a given concentration of an aqueous solution
Strong acids have a LOWER pH than weak acids for a given concentration of an aqueous solution
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As the pH decreases by one unit, the _______ ion concentration of the solution _______ by a factor of __.
As the pH decreases by one unit, the HYDROGEN ion concentration of the solution INCREASES by a factor of 10
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How do you check/compare the strength of acids?
React the two acids with metal carbonate, and time how long it takes for CO₂ to be produced (with a gas syringe)
Or look at the time taken for the metal to dissolve
Or look at the time taken for the metal to dissolve
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Formula of:
Hydrochloric acid
Sulfuric acid
Nitric acid
Hydrochloric acid
Sulfuric acid
Nitric acid
HCl⁻
H₂SO₄²⁺
HNO₃⁻
H₂SO₄²⁺
HNO₃⁻
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General equation:
acid + metal
acid + metal
acid + metal → salt + hydrogen
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How do we know which salt we produce?
What salt will be produced from HCl and H₂SO₄
What salt will be produced from HCl and H₂SO₄
It depends on the acid and metal that we're using.
HCl produces salts ending in chloride
H₂SO₄ produces salts ending in sulphate
HCl produces salts ending in chloride
H₂SO₄ produces salts ending in sulphate
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How does Mg react with HCl and H₂SO₄
hydrochloric acid + magnesium → magnesium chloride + hydrogen
sulphuric acid + magnesium → magnesium sulphate + hydrogen
sulphuric acid + magnesium → magnesium sulphate + hydrogen
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Zinc and Magnesium react ________ with acids
Iron reacts ________ with acids
Iron reacts ________ with acids
Zinc and Magnesium react QUICKLY with acids
Iron reacts SLOWLY with acids
Iron reacts SLOWLY with acids
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Why do Mg and Zn react quickly with acids, but Fe reacts slowly with acids?
Zn and Mg are much higher than hydrogen in the reactivity series so they displace it more easily than iron, which is closer to hydrogen
Mg easily forms Mg²⁺, Zn quite easily forms Zn²⁺, Fe less easily forms Fe²⁺
Mg easily forms Mg²⁺, Zn quite easily forms Zn²⁺, Fe less easily forms Fe²⁺
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What do salts contain (in terms of ions)?
Salts contain a positive ion which comes from the base/alkali
Salts also contain a negative ion which comes from the acid
Salts also contain a negative ion which comes from the acid
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How can soluble salts be made?
By reacting acids with solid insoluble substances, such as metals, metal oxides, hydroxides or carbonates
The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt.
The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt.
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How can solid salts be produced from salt solutions?
Salt solutions can be crystallised to produce solid salts.
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Required practical:
Method for forming a salt from a solid base (or metal)
Method for forming a salt from a solid base (or metal)
• Measure 50cm₃ acid in beaker + warm the acid
• Add spatulas of solid base (or metal)+ stir
• Keep adding solid until no more reacts and base is in excess
• Filter off excess solid base with filter funnel and
filter paper
• Add spatulas of solid base (or metal)+ stir
• Keep adding solid until no more reacts and base is in excess
• Filter off excess solid base with filter funnel and
filter paper
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Required practical:
Method for forming a salt from a solid base (or metal) cont.
Method for forming a salt from a solid base (or metal) cont.
• Pour solution into evaporating basin + heat using a Bunsen burner to crystallisation point, leave to crystallise
• Dry crystals on filter paper
• Dry crystals on filter paper
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Universal indicator colours
Red pH 1-2 strong acid
Orange/yellow pH3-6 weak acid
Green pH7 neutral
blue pH8-11 weak alkali
Purple pH 12-14 strong alkali
Orange/yellow pH3-6 weak acid
Green pH7 neutral
blue pH8-11 weak alkali
Purple pH 12-14 strong alkali
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Compare dilute and concentrated acids
How can you make a conc. acid into a dilute acid?
How can you make a conc. acid into a dilute acid?
A concentrated acid will have more moles of acid per unit volume than a dilute acid. A concentrated acid is made into a dilute acid by adding water.
Dilute and concentrated does not mean the same as strong and weak
Dilute and concentrated does not mean the same as strong and weak
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If an acid is diluted 10 times its pH will increase by ____ unit(s)
e.g. if a solution of HCl has a concentration of 0.01 mol/dm₃ it will have a pH of 2. If it is then diluted a 100 times it will have a pH of _.
e.g. if a solution of HCl has a concentration of 0.01 mol/dm₃ it will have a pH of 2. If it is then diluted a 100 times it will have a pH of _.
If an acid is diluted 10 times its pH will increase by ONE unit
e.g. if a solution of HCl has a concentration of 0.01 mol/dm₃ it will have a pH of 2. If it is then diluted a 100 times it will have a pH of 4.
e.g. if a solution of HCl has a concentration of 0.01 mol/dm₃ it will have a pH of 2. If it is then diluted a 100 times it will have a pH of 4.
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Strong acids have a ______ pH than weak acids for a given concentration
Strong acids have a LOWER pH than weak acids for a given concentration
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Other cards in this set
Card 2
Front
All metals above ______ in the reactivity series will react with acids producing bubbles of _______ gas
Back
All metals above HYDROGEN in the reactivity series will react with acids producing bubbles of HYDROGEN gas
Card 3
Front
Reactions of acid and metals are _____ reactions
Back
Card 4
Front
What can acids be neutralised by?
Back
Card 5
Front
General equation:
acid + base
acid + base
Back
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