0.01 moles of an alkene needed 2.4g of oxygen for complete combustion. 2.2g of carbon dioxide were formed. Determine the following mole ratio.
moles of alkene : moles of O2 : moles of CO2
From this ratio determine the formula of the alkene.
Write an equation for the complete combustion of this alkene.
The general chemical formula for an alkene is `C_nH_(2n)`
and the complete combustion reaction is:
`C_nH_(2n) + 3/2 nO_2 -> nCO_2 + nH_2O`
The molecular weight for oxygen is 32 gm/mole, carbon dioxide is 44 gm/mole and water is 18 gm/mole.
1 mole of alkene uses 1.5 mole oxygen and releases 1 mole carbon dioxide.
or, 1 mole alkene: 1.5 mole oxygen: 1 mole carbon dioxide
With the given data, the molar ratio is:
0.01 moles of alkene: 2.4/32 mole oxygen: 2.2/44 gm carbon dioxide
or, 0.01 mole alkene : 0.075 mole oxygen: 0.05 mole carbon dioxide
or, 1 mole alkene: 7.5 mole oxygen: 5 mole carbon dioxide
comparing the given data and stoichiometric ratio, correspondence will be there, if n=5.
or, `C_5H_(10) + 15/2 O_2 -> 5CO_2 + 5H_2O`
if you solve this chemical equation, you will find 0.01 mole alkene reacts with 0.075 mole oxygen and releases 0.05 moles of carbon dioxide.
hope this helps.