# What volume of the gas absorbed by the alkali ?

## Homework Statement

A mixture of 10cm^3 of methane and 10cm^3 of ethane was sparked with an excess oxygen . After cooling to room temperature , the residual gas was passed through aqueous potassium hydroxide

What volume of the gas absorbed by the alkali ?

N/A

## The Attempt at a Solution

I have no idea for the solution . Any hint ?

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what are the results of 'sparking' methane and ethane with oxygen? i.e. what are the products of combustion?

Water and carbon dioxide . I think . So..?

Gokul43201
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Gold Member
And what kind of gas is carbon dioxide? What happens when you pass such a gas through an alkaline solution like KOH?

And what kind of gas is carbon dioxide? What happens when you pass such a gas through an alkaline solution like KOH?

I have no idea . Guide pls .

Gokul43201
Staff Emeritus
Gold Member
KOH is a base. What do bases (or basic/alkaline solutions) react with?

I only know that acid react with base will produce water and salt .

Gokul43201
Staff Emeritus
Gold Member
Good, then keep in mind that CO2 is an acidic oxide. It is something like an acid, minus the water. It too, will react with a base, forming a salt. The point of this is to recognize that when you pass a gaseous mixture containing CO2 through a solution of KOH, all (or a very large part of) the CO2 will be removed by this reaction.

Write down and balance the equations for the combustion of ethane and methane. How much CO2 is produced from the given quantities?

Last edited:
I think the equation is as below :

For methane combustion :
CH4 + O2 ---> CO2 + H2O
Since 1 mole of CH4 : 1 mole of CO2
SO: 10CM^3 CH4 will gives 10 cm^3 CO2

For ethane combustion :
C2H6 + O2 ---> CO2 + H2O
Since 1 mole of C2H6 : 1 mole of CO2
So: 10cm^3 C2H6 will gives 20 cm^3 CO2

Total gas has absorbed is 30 cm^3 ?
Am I correct ?

Last edited:
Gokul43201
Staff Emeritus
Gold Member
You have not balanced the equations. You need to do that before you determine the mole ratios.

I think the equation is as below :

For methane combustion :
CH4 + O2 ---> CO2 + H2O
Since 1 mole of CH4 : 1 mole of CO2
SO: 10CM^3 CH4 will gives 10 cm^3 CO2

For ethane combustion :
C2H6 + O2 ---> CO2 + H2O
Since 1 mole of C2H6 : 1 mole of CO2
So: 10cm^3 C2H6 will gives 20 cm^3 CO2

Total gas has absorbed is 30 cm^3 ?
Am I correct ?

{EDIT}
For methane combustion :
CH4 + 3O2 ---> CO2 + 2H2O
Since 1 mole of CH4 : 1 mole of CO2
SO: 10CM^3 CH4 will gives 10 cm^3 CO2

For ethane combustion :
C2H6 + 7/2O2 ---> 2CO2 + 3H2O
Since 1 mole of C2H6 : 2 mole of CO2
So: 10cm^3 C2H6 will gives 20 cm^3 CO2 ?

so
total volume is 30cm^3 ?

Gokul43201
Staff Emeritus