Question

A fuel has octane no. of 60. This indicates that fuel has the knocking tendency equal to:
A. $60\%$ n-heptane + $40\%$ iso-octane
B. $60\% \,$ n-octane + $\,40\%$ iso-heptane
C. $60\%$ iso-octane + $40\%$ n-heptane
D. $60\%$ iso-heptane + $\,40\%$ n-octane

Answer 1

Octane rating number is the measurement for the fuel's capability to overcome knocking or pinging ability of fuel during the combustion, caused by the air mixture or fuel mixture detonating prematurely inside the engine.

Complete answer:
The octane rating number is basically displayed in large black numbers on a yellow background color on gasoline or fuel pumps or in the other words Octane rating or octane number is a measure of overall performance of fuel for total internal combustion inside the engines. therefore a higher octane rating has relatively more engine power and less pinging or other before ignition problems. A low-performance engine will not normally perform better when the octane number or rating of that fuel is high, therefore the compression ratio is fixed for octane rating by the engine design. The RON i.e, Research Octane Number is calculated by combustion of the fuel in a test engine with a differentiating compression ratio under fully controlled situations, and then comparing all the output results with those for mixtures of iso-octane and n-heptane.
The octane rating of fuel is measured in a testing engine and is calculated by relating it with the mixture of $2,2,4 -$trimethylpentane, (iso-octane) and heptane that would have the same anti-knocking ability as the fuel under test. The percentage, by total volume, of $2,2,4 -$trimethylpentane in that mixture is the octane number of the fuel.

**Therefore the correct answer is option C.$60\%$ iso-octane+ $$$$40\% n-heptane.

Note: **
Octane rating or octane number does not relate to the energy content of the particular fuel but it is only a measurement of the fuel's ability to burn rather than to explode.