General equation for combustion :CxHy + (x+y/4)O2 → xCO2 + y/2H2O​According to question :(x+(y/4))/x = 7/4Solving the equation we obtain:4x + y = 7x ory=3xy/x = 3/1Thus the alkane is of the type:CxH3xGaseous alkanes are CH4 , C2H6 , C3H8 ,C4H10 only and only gaseous alkane with formula of this type is C2H6.

balance the eqtn of combustion. CxHy + (x+y/4)O2 gives xCO2+ y/2H2O ratio is 7:4 that means x+(y/4) O2 /x =7/4 u will get x=y/3 which satisfies the answer

Introduction:
In this scenario, a gaseous alkane was exploded with oxygen, resulting in the formation of carbon dioxide (CO2). The ratio of the volumes of oxygen to carbon dioxide formed during the complete combustion of the alkane is given as 7:4. We need to determine the molecular formula of the alkane based on this information.

Understanding Combustion Reaction:
Combustion reactions involve the reaction of a substance with oxygen, resulting in the release of energy in the form of heat and light. In the case of hydrocarbons like alkanes, the products of combustion are carbon dioxide and water. The balanced equation for the complete combustion of an alkane is:

CnH(2n+2) + (3n+1)/2 O2 → nCO2 + (n+1)H2O

Using the Volume Ratio:
The given information states that the volume ratio of oxygen to carbon dioxide formed during the combustion of the alkane is 7:4. This ratio can be converted into a mole ratio by considering the ideal gas law and assuming constant temperature and pressure. Since the volume ratio is given, we can directly consider the mole ratio of the gases.

Determining the Molecular Formula:
To determine the molecular formula of the alkane, we need to find the value of n in the balanced equation. By comparing the mole ratio of oxygen to carbon dioxide (7:4) with the balanced equation, we find:

7 moles of O2 reacts with n moles of CnH(2n+2) to form 4 moles of CO2

From this, we can set up the following equation:

7/4 = n/1

Cross-multiplying, we get:

7 = 4n

Simplifying:

n = 7/4

Thus, the value of n is 7/4. However, n must be a whole number since it represents the number of carbon atoms in the alkane's molecular formula. Therefore, we need to multiply both sides of the equation by 4 to eliminate the fraction:

n = 7/4 * 4

n = 7

Conclusion:
Based on the given information, the molecular formula of the alkane is C7H(2(7)+2) = C7H16.