Question
What volume of oxygen at STP is required to affect complete combustion of 200 cm3 of acetylene and what would be the volume of carbondioxide formed?
Solution
The chemical equation representing the combustion of acetylene is
(i) To calculate the volume of O2 at STP required to effect complete combustion of 200 cm3 of acetylene:
According to Gay Lussac’s law of gaseous volumes,
2 volumes C2H2 will require O2 for complete combustion = 5 vol
200 cm3 C2H2 will require O2 for complete combustion = 
= 500 cm3 at STP
Thus volume of O2 required = 500 cm3 at S.T.P.
(ii) To calculate the volume of CO2 produced at S.T.P
According to Gay Lussac’s law of gaseous volumes.
2 volumes of C2H2 produce CO2 = 4 vol
200 cm3 C2H2 at S.T.P. will produce CO2
volume of CO2 produced = 400 cm3 at STP
(i) To calculate the volume of O2 at STP required to effect complete combustion of 200 cm3 of acetylene:
According to Gay Lussac’s law of gaseous volumes,
2 volumes C2H2 will require O2 for complete combustion = 5 vol
200 cm3 C2H2 will require O2 for complete combustion = = 500 cm3 at STP
Thus volume of O2 required = 500 cm3 at S.T.P.
(ii) To calculate the volume of CO2 produced at S.T.P
According to Gay Lussac’s law of gaseous volumes.
2 volumes of C2H2 produce CO2 = 4 vol
200 cm3 C2H2 at S.T.P. will produce CO2 volume of CO2 produced = 400 cm3 at STP
