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A student carried out an investigation to determine the order of reactivity of four metals, W, X, Y and Z - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2022 - Paper 1
Question 6
A student carried out an investigation to determine the order of reactivity of four metals, W, X, Y and Z. A piece of metal W was added to a test tube containing exc... show full transcript
Worked Solution & Example Answer:A student carried out an investigation to determine the order of reactivity of four metals, W, X, Y and Z - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2022 - Paper 1
Step 1
Use the information in Figure 6 to place the metals in order of reactivity from the least reactive to the most reactive.
Answer
From the observations:
- Metal Z: Bubbles formed very quickly with no metal remaining, indicating it is the most reactive.
- Metal Y: Bubbles formed quickly and all the metal reacted, making it the next most reactive.
- Metal W: Bubbles formed quickly but some metal remained, placing it after Y.
- Metal X: Only a few bubbles were formed and the metal remained unchanged, placing it as the least reactive.
Thus, the order is: X → W → Y → Z.
Step 2
Explain why the reaction between metal Y and excess dilute sulfuric acid stopped even though there was solid metal Y left.
Answer
The reaction between metal Y and excess dilute sulfuric acid stopped because the concentration of hydrogen ions (H⁺) in the vicinity of the metal surface decreased as the reaction progressed. The hydrogen ions react with the metal, leading to the formation of hydrogen gas and metal sulfate, represented as:
ightarrow ext{metal sulfate} + ext{hydrogen}$$ As the reaction occurs, the remaining solid metal Y becomes covered with a layer of metal sulfate, which acts as a barrier, preventing further contact between the acid and the metal. This barrier limits the availability of H⁺ ions to react with the solid metal Y, thus stopping the reaction.