Chemical Formulae, Equations and Calculations Part 1
3 marks · EasyAnswer the questions about carbon dioxide, CO2.
(a)[1 mark]
State the relative atomic masses (Ar) for C and O.
(b)[1 mark]
Calculate the relative formula mass (Mr) of CO2.
(c)[1 mark]
What is the mass of 0.25 mol of carbon dioxide?
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(a) C = 12, O = 16 · must show C = 12, O = 16
(b) 44 · must show Mr = 12 + (2 × 16) = 44
(c) 11 g · must show mass = 0.25 × 44 = 11
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Marking points
B1 (a) · 1 mark · Gives correct Ar for C (12) and O (16).
B2 (b) · 1 mark · Gives correct Mr for CO2 (44).
B3 (c) · 1 mark · Correct mass of 0.25 mol CO2 is 11 g.
Worked solution
a) C = 12, O = 16
b) Mr(CO2) = 12 + (2 × 16) = 44
c) Mass = 0.25 × 44 = 11 g