Question:
What is the source of an alkane if its molar mass is 100 and the percentage by mass of hydrogen is 16?
What is the source of an alkane if its molar mass is 100 and the percentage by mass of hydrogen is 16?
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Alkanes with carbon number from C\(_5\) to C\(_9\) mainly occur in petrol.
Updated On: Feb 11, 2026
- Waxes
- Diesel
- LPG
- Petrol
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The Correct Option is D
Solution and Explanation
Step 1: Use the general formula of alkanes.
Alkanes have the general formula \( \mathrm{C_nH_{2n+2}} \).
Step 2: Express molar mass in terms of \(n\).
Molar mass \(= 12n + (2n+2) = 14n + 2 \).
Given molar mass \(= 100\).
\[ 14n + 2 = 100 \]
\[ 14n = 98 \Rightarrow n = 7 \]
Step 3: Identify the alkane.
For \(n = 7\), the alkane is heptane \(\mathrm{C_7H_{16}}\).
Step 4: Match with petroleum fractions.
Heptane is a major constituent of petrol (gasoline).
Step 5: Conclusion.
The given alkane belongs to the petrol fraction.
Alkanes have the general formula \( \mathrm{C_nH_{2n+2}} \).
Step 2: Express molar mass in terms of \(n\).
Molar mass \(= 12n + (2n+2) = 14n + 2 \).
Given molar mass \(= 100\).
\[ 14n + 2 = 100 \]
\[ 14n = 98 \Rightarrow n = 7 \]
Step 3: Identify the alkane.
For \(n = 7\), the alkane is heptane \(\mathrm{C_7H_{16}}\).
Step 4: Match with petroleum fractions.
Heptane is a major constituent of petrol (gasoline).
Step 5: Conclusion.
The given alkane belongs to the petrol fraction.
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