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A teacher investigates the reaction between hydrochloric acid and magnesium - OCR Gateway - GCSE Chemistry - Question 18 - 2023 - Paper 4
Question 18
A teacher investigates the reaction between hydrochloric acid and magnesium. The diagram shows the teacher’s experiment. The teacher uses five different concentrat... show full transcript
Worked Solution & Example Answer:A teacher investigates the reaction between hydrochloric acid and magnesium - OCR Gateway - GCSE Chemistry - Question 18 - 2023 - Paper 4
Step 1
Write the balanced symbol equation for the reaction between hydrochloric acid, HCl, and magnesium.
Answer
The balanced symbol equation for the reaction between hydrochloric acid and magnesium is:
ightarrow ext{MgCl}_2 + ext{H}_2 $$ This equation shows that two moles of hydrochloric acid react with one mole of magnesium to produce one mole of magnesium chloride and one mole of hydrogen gas.Step 2
Use the results to explain why the teacher is correct.
Answer
The teacher's statement that 'the reaction is faster the more concentrated hydrochloric acid' is supported by the results. As seen in the table, as the concentration of hydrochloric acid increases, the time taken for magnesium powder to react decreases significantly:
- At 0.5 mol/dm³ concentration, the reaction time is 117 seconds.
- At 1.0 mol/dm³, it drops to 82 seconds.
- Further increasing the concentration to 1.5 mol/dm³ results in a reaction time of only 48 seconds, and so on.
This trend indicates that a higher concentration of hydrochloric acid increases the frequency of collisions between acid molecules and magnesium, leading to a faster reaction.