AQA A-Level Chemistry Paper 3, 2023: Question 21

1 mark · Easy difficulty · Multiple Choice

Reaction of Barium with Water This question focuses on the observation when barium metal reacts with a large excess of water. The reaction produces hydrogen gas and barium hydroxide, and the question assesses the correct and complete description of this reaction.

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Question

AQA A-Level Chemistry Paper 3, 2023: Question 21
Question text

21 Barium metal is added to a large excess of water.

Which observation is correct and complete?

[1 mark]

A a colourless solution

B a colourless solution with effervescence

C a dense white precipitate

D a dense white precipitate with effervescence

Mark scheme

Show the mark scheme Mark scheme for AQA A-Level Chemistry Paper 3, 2023: Question 21

21 B 1 (AO1) a colourless solution with effervescence

How to answer it

Reaction of Barium Metal with Water

Question

Which observation is correct and complete when barium metal is added to a large excess of water?

  • A: A colourless solution
  • B: A colourless solution with effervescence
  • C: A dense white precipitate
  • D: A dense white precipitate with effervescence

Correct Answer: B

The correct observation is a colourless solution with effervescence . When barium reacts with water:

  • Bubbles of hydrogen gas are produced (effervescence).
  • The solution is colourless because barium hydroxide, which is formed, is soluble in water.

Explanation

The reaction of barium with water can be summarised as follows:

Equation:

Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2(g)

  • Effervescence: This is due to the release of hydrogen gas (H2).
  • Colourless solution: Barium hydroxide (Ba(OH)2) dissolves in water to give a clear, colourless solution.

Why Other Options Are Incorrect

  • A: While the solution is colourless, this option does not account for the effervescence caused by hydrogen gas.
  • C: Barium hydroxide is soluble in water, so no precipitate forms.
  • D: There is no precipitate in this reaction, so this option is incorrect.

Teacher Tip

Tip: Remember that group 2 metals react with water to produce an alkaline solution (hydroxide) and hydrogen gas. Solubility trends down the group determine whether a precipitate forms.

Topics

Inorganic Chemistry · 3.2.2 Group 2, the Alkaline Earth Metals

Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.