Reactivity Series
6 marks · NormalA student investigates how three different metals react with dilute sulfuric acid. The student uses equal moles of each metal under the same conditions.
| Metal | Temperature change / °C |
|---|---|
| Zinc | 9 |
| Iron | 5 |
| Copper | 0 |
Use the data to arrange the three metals from most reactive to least reactive with dilute sulfuric acid.
Write a balanced chemical equation (with state symbols) for the reaction between zinc and dilute sulfuric acid.
Explain why the student must use the same number of moles, rather than the same mass, of each metal to fairly compare their reactivity.
A metal called cobalt is placed between iron and copper in the reactivity series. Predict whether cobalt will react with dilute sulfuric acid under the same conditions. Give a reason for your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Zinc > Iron > Copper · must show Order: Zinc, Iron, Copper
(b) Zn(s) + H2SO4(aq) -> ZnSO4(aq) + H2(g) · must show Zn(s), H2SO4(aq), ZnSO4(aq), H2(g)
(c) A fair test requires the amount of substance (number of particles) to be the same for each metal; different masses have different numbers of particles because the metals have different relative atomic masses. · must show Same number of moles means same number of particles, Metals have different relative atomic masses
(d) Cobalt will not react with dilute sulfuric acid, as copper does not react and cobalt is less reactive than iron but more than copper (but still below hydrogen). · must show Cobalt will not react, Less reactive than hydrogen (since copper doesn't react)
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States correct order (most to least reactive): zinc, iron, copper.
M1 (b) · 1 mark · Writes a correct balanced equation for zinc with sulfuric acid (may omit or make minor error in state symbols).
A1 (b) · 1 mark · All correct state symbols present: Zn(s) + H2SO4(aq) -> ZnSO4(aq) + H2(g).
M1 (c) · 1 mark · Explains use of moles for direct comparison (amount of particles, not mass, should be the same).
A1 (c) · 1 mark · Mentions that different metals have different relative atomic masses (so same masses mean different moles).
B1 (d) · 1 mark · Correctly predicts cobalt will not react with dilute sulfuric acid, and gives a correct reason referring to the series or copper.
Worked solution
a) From the data, zinc produces the largest temperature change, followed by iron, then copper has none. So the order: zinc > iron > copper.
b) The balanced chemical equation (with state symbols) is: Zn(s) + H2SO4(aq) -> ZnSO4(aq) + H2(g)
c) To fairly compare reactivity, the number of particles (moles) of each metal must be the same; otherwise, the metal with more particles would seem more reactive even if it is not. Different metals have different atomic masses, so the same mass gives a different number of particles.
d) Cobalt is between iron and copper in the series. Copper does not react, and iron does. Therefore, cobalt is unlikely to react with dilute sulfuric acid because it is below hydrogen (or very close), and so would not displace hydrogen from acid.