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...

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. 

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gsenviro | College Teacher | (Level 1) Educator Emeritus

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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.

Using stoichiometry,

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.

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