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butane in a limited amount of oxygen

A 30cm3 sample of butane, C4H10, was completely reacted in a limited supply of oxygen to produce 60 cm3 of carbon dioxide and 60 cm3 of carbon monoxide.
All volumes were measured at room temperature and pressure.
Which volume of oxygen was used?

A 90cm3 B 120cm3 C 150cm3 D 165cm3

(answer D, but why?)
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1 Answer

Write the balanced equation for this combustion reaction noting that that CO and CO2 that are produced are in equal amounts (60 ml) so are in 1:1 ratio in the balanced equation.
2 C4H1O + 11 O2 ===> 4 CO2 + 4 CO + 10 H2O
Now, simply solve for the 11 oxygens as a volume, given that you started with 30 cm3 of butane:
30 cm3 butane x 11 cm3 O2/2 cm3 butane = 165 cm3 O2
NOTE:  In this type of problem, the volume are equivalent to moles, so in the balanced equation, the coefficients can be viewed as moles, cm3, liters, etc.