A gaseous hydrocarbon having Carbon less than 5 is burnt with sufficient amount of oxygen. The volume of reactants was found to be 600 ml. After explosion, the volume of products (Carbon dioxide and water in gaseous form) was found to be 700 ml. Find the molecular formula of the hydrocarbon. (Answer: propane) please tell the solution.

To determine the molecular formula of the hydrocarbon in question, we need to analyze the combustion reaction and apply the principles of stoichiometry. The problem states that we have a gaseous hydrocarbon with fewer than five carbon atoms, and upon combustion with sufficient oxygen, the volume of products is greater than the volume of reactants. Let's break this down step by step.

Step 1: Understanding Combustion of Hydrocarbons

When a hydrocarbon (C_xH_y) combusts in the presence of oxygen (O₂), it produces carbon dioxide (CO₂) and water (H₂O). The general reaction can be represented as:

C_xH_y + O₂ → CO₂ + H₂O

Step 2: Analyzing the Given Data

We know the following from the problem:

• Volume of reactants (hydrocarbon + oxygen) = 600 ml
• Volume of products (CO₂ + H₂O) = 700 ml

This increase in volume after combustion suggests that the hydrocarbon is producing more gaseous products than the volume of reactants consumed. This is typical for hydrocarbons, especially when they contain three or more carbon atoms.

Step 3: Setting Up the Reaction

Assuming the hydrocarbon is propane (C₃H₈), we can write the balanced equation for its combustion:

C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O

Step 4: Calculating Volumes

From the balanced equation, we can see that:

• 1 volume of propane reacts with 5 volumes of oxygen.
• This produces 3 volumes of carbon dioxide and 4 volumes of water vapor.

Thus, the total volume of products formed is:

3 (CO₂) + 4 (H₂O) = 7 volumes

Step 5: Relating Reactants to Products

Now, let's relate the volumes of reactants to the products. If we assume the volume of propane used is V ml, then the volume of oxygen consumed would be 5V ml. Therefore, the total volume of reactants can be expressed as:

V + 5V = 6V

Setting this equal to the given volume of reactants:

6V = 600 ml

Solving for V gives:

V = 100 ml

Step 6: Verifying Product Volume

Now, substituting V back into our product volume calculation:

Products = 3 (from CO₂) + 4 (from H₂O) = 7 volumes of V

So, the total volume of products is:

7 * 100 ml = 700 ml

Final Thoughts

Since the calculations align perfectly with the data provided in the problem, we can confidently conclude that the molecular formula of the hydrocarbon is indeed propane (C₃H₈). This example illustrates how stoichiometry and the principles of gas behavior during combustion can help us identify unknown compounds based on their reactions.