A fuel cell is an electrochemical cell that can be used to generate electrical energy by using oxygen to oxidise a fuel. Methanoic acid, HCOOH , is being investigated as a fuel in fuel cells. When the cell operates, HCOOH is oxidised to carbon dioxide. The half-equation for the reaction at the cathode is: $$$\mathrm{O}_{2}+4 \mathrm{H}^{+}+4 \mathrm{e}^{-} \rightarrow 2 \mathrm{H}_{2} \mathrm{O}$$$. In this fuel cell, the overall cell reaction is the same as that for the complete combustion of HCOOH . (i) Deduce the half-equation for the reaction at the anode. ................................................................................................................................. (ii) Calculate the volume, in $$$\mathrm{cm}^{3}$$$, of oxygen used when a current of 3.75 A is delivered by the cell for 40.0 minutes. Assume the cell operates at room conditions. volume of oxygen = .......................... cm

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s24_qp_42 Year：2024 Question No：6(d)

Answer:

Knowledge points:

6.1.1 calculate oxidation numbers of elements in compounds and ions

6.1.2 use changes in oxidation numbers to help balance chemical equations

6.1.3 explain and use the terms redox, oxidation, reduction and disproportionation in terms of electron transfer and changes in oxidation number

6.1.4 explain and use the terms oxidising agent and reducing agent

6.1.5 use a Roman numeral to indicate the magnitude of the oxidation number of an element

8.1.1 explain and use the term rate of reaction, frequency of collisions, effective collisions and non-effective collisions

8.1.2 explain qualitatively, in terms of frequency of effective collisions, the effect of concentration and pressure changes on the rate of a reaction

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