1(vii)
Rita added dilute hydrochloric acid to four metals. She recorded her observations in the table given below. While noting her observations she made some errors.
| Metals | Observations | |
|---|---|---|
| 1 | copper | a gas was given off |
| 2 | iron | a gas was given off |
| 3 | magnesium | no gas was given off |
| 4 | zinc | a gas was given off |
Which observation(s) made by Rita is/are correct?
- (a)1 only
- (b)3 only
- (c)Both 1 and 4
- (d)Both 2 and 4
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Both 2 and 4
Reason — The reactivity of these metals with dilute HCl depends on their position in the activity series:
- Copper lies below hydrogen in the activity series, so it does not react with dilute HCl. Hence, no gas is given off — observation (1) is incorrect.
- Iron is above hydrogen in the activity series, hence it reacts with dilute HCl liberating hydrogen gas — observation (2) is correct.
Fe + 2HCl ⟶ FeCl2 + H2 ↑ - Magnesium is highly reactive and reacts vigorously with dilute HCl liberating hydrogen gas — observation (3) is incorrect.
Mg + 2HCl ⟶ MgCl2 + H2 ↑ - Zinc is above hydrogen in the activity series and reacts with dilute HCl liberating hydrogen gas — observation (4) is correct.
Zn + 2HCl ⟶ ZnCl2 + H2 ↑
Hence, observations 2 and 4 are correct.