In an experiment, powdered calcium hydroxide was added to dilute hydrochloric acid and the pH was measured - Edexcel - GCSE Chemistry Combined Science - Question 1 - 2023 - Paper 1
Question 1
In an experiment, powdered calcium hydroxide was added to dilute hydrochloric acid and the pH was measured.
The method used was
step 1 measure 200 cm³ dilute hydroc... show full transcript
Worked Solution & Example Answer:In an experiment, powdered calcium hydroxide was added to dilute hydrochloric acid and the pH was measured - Edexcel - GCSE Chemistry Combined Science - Question 1 - 2023 - Paper 1
Step 1
State what should be done after step 2 to make sure that any reaction is complete.
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Answer
After step 2, the mixture should be stirred or shaken to ensure that the powdered calcium hydroxide fully dissolves and reacts with the hydrochloric acid.
Step 2
Complete the word equation for the reaction.
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Answer
calcium hydroxide + hydrochloric acid → calcium chloride + water
Step 3
Which row of the table shows the state symbols for powdered calcium hydroxide and dilute hydrochloric acid in the balanced chemical equation?
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Answer
The correct row is A, where calcium hydroxide is in solid state (s) and hydrochloric acid is in aqueous state (aq).
Step 4
Using Figure 1, give the pH of the acid at the start of the experiment.
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Answer
pH = 1
Step 5
Using Figure 1, give the mass of calcium hydroxide required to make a neutral mixture.
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Answer
mass of calcium hydroxide = 0.7 g
Step 6
Explain why the pH starts at a low value and ends at a higher value.
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Answer
The pH starts at a low value because hydrochloric acid is a strong acid, resulting in a low pH. As calcium hydroxide is added, it reacts with the acid, neutralizing it and forming water and calcium chloride, which raises the pH towards neutral as the reaction proceeds.
