DSE Chemistry
DSE Chemistry: Acids and Bases — Practice Questions & Answers
Properties of acids and alkalis, indicators and the pH scale, neutralisation and salt preparation, titration, and concentration calculations.
402 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Medium
A small amount of a powder dissolves in water to give a colourless solution. When mixed with K2CO3(aq), a white precipitate forms. The powder could be
- calcium chloride
- sodium sulphate
- sodium nitrate
- potassium chloride
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WhyCa2+ gives insoluble white CaCO3; sodium salts remain dissolved.
2
Multiple choice · Easy
Which of the following salts is INSOLUBLE in water?
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WhyCalcium carbonate is an insoluble carbonate.
3
Multiple choice · Medium
Which ionic equation represents the reaction that gives the white precipitate?
- Ca2+(aq) + CO3 2-(aq) -> CaCO3(s)
- Na+(aq) + Cl-(aq) -> NaCl(s)
- Ca2+(aq) + 2 OH-(aq) -> Ca(OH)2(s)
- 2 K+(aq) + CO3 2-(aq) -> K2CO3(s)
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WhyCa2+ combines with CO3 2- to give insoluble CaCO3.
4
Fill in the blank · Medium
Mixing calcium chloride solution with sodium carbonate solution produces an insoluble white of calcium carbonate.
Answer:
precipitate / ppt
WhyThis is a precipitation reaction.
5
Fill in the blank · Easy
All sodium, potassium and salts are soluble in water, so they never form precipitates.
Answer:
ammonium / ammonium (NH4+)
WhyThis is a key solubility rule.
6
Fill in the blank · Medium
The spectator ions in the precipitation of CaCO3 from CaCl2(aq) and Na2CO3(aq) are Na+ and .
Answer:
Cl- / chloride / Cl- (chloride)
WhyThey remain unchanged in solution.
7
Multiple choice · Medium
Which of the following statements concerning CH3COOH and HCl is correct?
- Both CH3COOH(aq) and HCl(aq) react with NH3(aq), each giving a salt
- CH3COOH is a stronger acid than HCl
- The pH of 0.1 M CH3COOH(aq) is lower than that of 0.1 M HCl(aq)
- Both react with Ag(s) to give a gas
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WhyAt equal concentration HCl is fully ionised, so 0.1 M HCl has a lower pH than 0.1 M CH3COOH; both are neutralised by ammonia to give a salt.
8
Multiple choice · Medium
At the same concentration, 0.1 M HCl(aq) has a lower pH than 0.1 M CH3COOH(aq) because
- HCl ionises completely but CH3COOH only partially
- HCl is more concentrated
- CH3COOH contains more hydrogen atoms
- CH3COOH is a strong acid
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WhyHCl ionises completely while ethanoic acid ionises only partially, so HCl gives a higher H+ concentration.
9
Multiple choice · Easy
Ethanoic acid is classified as a weak acid because it
- only partially ionises in water
- is always dilute
- does not contain hydrogen
- cannot be neutralised
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WhyA weak acid only partially ionises in water.
10
Fill in the blank · Medium
At equal concentration, the strong acid HCl gives a pH than the weak acid ethanoic acid.
Answer:
lower
WhyFull ionisation produces more H+ ions.
Key terms in Acids and Bases
Acid: A substance that releases hydrogen ions (H+) when dissolved in water.
Base: A substance that reacts with an acid to form a salt and water.
Alkali: A soluble base that releases hydroxide ions (OH-) when dissolved in water.
Neutralisation: The reaction between an acid and a base to produce a salt and water only.
pH: A measure of acidity defined as pH = -log[H+], with values below 7 acidic and above 7 alkaline.
Indicator: A substance that changes colour according to the pH of a solution.
Universal indicator: A mixture of indicators that shows a range of colours across the whole pH scale.
Salt: An ionic compound formed when the hydrogen of an acid is replaced by a metal or ammonium ion.
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