Given Data:
- Gaseous mixture contains CO, C2H6, and C2H4.
- CO constitutes 40% by volume of the mixture.
- 250 ml of the mixture is burnt completely in the presence of excess oxygen.

Objective:
Find the total volume of CO2 formed during the combustion process.

Solution:

Step 1: Calculation of Volume of CO
Given that CO constitutes 40% by volume of the mixture, we can calculate the volume of CO as follows:

Volume of CO = 40% of 250 ml
Volume of CO = (40/100) * 250 ml
Volume of CO = 100 ml

Step 2: Calculation of Volume of C2H6
Since we know that the gaseous mixture is burnt completely in the presence of excess oxygen, it means that all the carbon in C2H6 will be converted into CO2.

To calculate the volume of C2H6, we need to consider the stoichiometry of the combustion reaction:

2 C2H6 + 7 O2 → 4 CO2 + 6 H2O

From the balanced equation, we can see that for every 2 moles of C2H6, 4 moles of CO2 are formed.

Let's assume the volume of C2H6 is V ml. Since the volume of CO2 formed will be the same as the volume of C2H6, we can write the following equation:

V ml of C2H6 → V ml of CO2

From the stoichiometry of the reaction, we know that 2 moles of C2H6 will produce 4 moles of CO2.

Therefore, we can write the following equation:

2 moles of C2H6 → 4 moles of CO2

Now, we can set up the proportion:

2 moles of C2H6 / 4 moles of CO2 = V ml of C2H6 / V ml of CO2

Simplifying the equation, we get:

1 mole of C2H6 / 2 moles of CO2 = 1 ml of C2H6 / 1 ml of CO2

Since we know that the volume of CO2 is equal to the volume of C2H6, we can substitute V ml for both:

1 ml of C2H6 / 2 ml of CO2 = 1 ml of C2H6 / 1 ml of CO2

Therefore, the volume of C2H6 is 2 times the volume of CO2.

So, the volume of C2H6 = 2 * 100 ml (volume of CO) = 200 ml

Step 3: Calculation of Volume of C2H4
Since the gaseous mixture is burnt completely, all the carbon in C2H4 will also be converted into CO2.

The stoichiometry of the combustion reaction for C2H4 is as follows:

C2H4 + 3 O2 → 2 CO2 + 2 H2O

From the balanced equation, we can see that for every 1 mole of C2H4, 2 moles of CO2 are formed.

Let's assume the volume of C2H4 is