Reactivity Series
6 marks · NormalThis question is about metals reacting with both solutions of salts and with water.
State the general equation for the reaction of a metal with cold water.
Iron does not react with cold water, but does react with copper(II) sulfate solution.
Write the ionic equation for the reaction between iron and copper(II) sulfate solution.
Give a reason why iron reacts with copper(II) sulfate solution but not with cold water.
Potassium reacts vigorously with cold water. Complete the ionic equation for this reaction and identify the gas produced:
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(a) metal + cold water → metal hydroxide + hydrogen
(b(i)) Fe(s) + Cu^{2+}(aq) \rightarrow Fe^{2+}(aq) + Cu(s)
(b(ii)) Iron is above copper in the reactivity series but below hydrogen, so it is able to displace copper from copper(II) sulfate but cannot react with water.
(c) H_2; hydrogen
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Marking points
B1 (a) · 1 mark · States correct general equation for reaction of metal with cold water.
M1 (b(i)) · 1 mark · Attempts correct balanced ionic equation for iron and copper(II) sulfate.
A1 (b(i)) · 1 mark · Correct states and balanced equation with correct ions.
B2 (b(ii)) · 1 mark · Gives reason using reactivity series (iron less reactive than hydrogen, more reactive than copper).
M2 (c) · 1 mark · Completes ionic equation with correct formula for hydrogen.
B3 (c) · 1 mark · Identifies the gas as hydrogen.
Worked solution
a) The general equation for a reaction of a metal with cold water is:
b)(i) The ionic equation for the reaction between iron and copper(II) sulfate solution is:
b)(ii) Iron is above copper in the reactivity series but below hydrogen, so it can displace copper from copper(II) sulfate solution but is not reactive enough to react with cold water.
c) The missing gas in the equation is hydrogen:
The gas produced is hydrogen.