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Chapter 24: Problem 19

What is the octane number of a mixture that is \(35 \%\) heptane and \(65 \%\) isooctane?

Short Answer

Expert verified
The octane number of a mixture that is 35% heptane and 65% isooctane can be calculated using the volume-weighted average formula. The result is an octane number of 65 for the mixture.

Step by step solution

01

Understand the octane rating

The octane rating is a measure of a fuel's ability to resist 'knock' or 'pinging' during combustion, caused by the air/fuel mixture detonating prematurely in the engine. In the scale, heptane is given a value of 0 and isooctane is given a rating of 100. This means that isooctane can withstand higher compression than heptane before detonating.
02

Identify the volume percentages of the compounds in the mixture

The exercise states that the mixture is composed of 35% heptane and 65% isooctane. This means that for every 100 litres of fuel, there will be 35 litres of heptane and 65 litres of isooctane.
03

Calculate the octane number of the mixture

The octane number of a mixture can be calculated by taking the volume-weighted average of the octane numbers of each component. This can be done using the formula: \(\text{Octane number} = (\text{% Heptane} \times \text{Heptane's octane number}) + (\text{% Isooctane} \times \text{Isooctane's octane number})\) Substitute the given values into the formula: \(\text{Octane number} = (35\% \times 0) + (65\% \times 100) = 0 + 65 = 65\) So, the octane number of the mixture is 65.

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Most popular questions from this chapter

Indicate whether each statement is true or false: (a) Fat molecules must contain \(\mathrm{C}=\mathrm{C}\) bonds. (b) Phosphoplipids have overall net charge. (c) Cis-monounsaturated fat molecules are bent in shape.

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