IB Chemistry SL R1.3 Energy from fuels questions

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Type
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Question 1

Paper 2Easy6 marks

An ethanol burner used to heat food burns ethanol in a plentiful supply of oxygen. Figure 1 shows the structural formula of ethanol.

CH3CH2OH
(a)

Use Figure 1 to state the molecular formula of ethanol.

[1]
(b)

Write a balanced equation for the complete combustion of ethanol.

[2]
(c)

A sample of 0.350 mol of ethanol burns completely. Using the equation in (b), calculate each amount in mol to three significant figures.

(i)

Oxygen consumed

[1]
(ii)

Carbon dioxide formed

[1]
(d)

Identify the oxidizing agent in the combustion reaction.

[1]

Question 2

Multiple choiceMedium1 mark

A sensor is powered by a hydrogen fuel cell supplied with hydrogen and oxygen. It ceases operating when its hydrogen supply is exhausted. Which paired description accounts for the energy conversion and distinguishes the cell from a primary cell?

Show answer and explanation

Answer: D. A fuel cell converts chemical energy directly to electrical energy. Its reactants are supplied continuously, whereas the reactants of a primary cell are contained within the cell.

A: incorrectly extends continuous external reactant supply to primary cells. B: inserts heat as an intermediate energy form; the reactant-supply distinction is correct. C: reverses the reactant arrangements of fuel cells and primary cells.

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