The density of ethanol is 1.09 g/cm³ The density of propylene is 0.97 g/cm³ 60 litres of ethanol are mixed with 128 litres of propylene to make 188 litres of antifreeze - Edexcel - GCSE Maths - Question 14 - 2019 - Paper 3

To find the mass of propylene, use the same formula:

$\text{Mass}_{\text{propylene}} = 0.97\,\text{g/cm}^3 \times 128\,\text{litres} = 0.97 \times 128 \times 1000\,\text{g} = 12416\,\text{g}$

The total mass of the antifreeze mixture is given by:

$\text{Total Mass} = \text{Mass}_{\text{ethanol}} + \text{Mass}_{\text{propylene}}$

Calculating this gives:

$\text{Total Mass} = 65400\,\text{g} + 12416\,\text{g} = 77816\,\text{g}$

The density of the antifreeze can now be calculated using the formula:

$\text{Density} = \frac{\text{Total Mass}}{\text{Total Volume}}$

The total volume is 188 litres, which is equivalent to 188000 cm³:

$\text{Density}_{\text{antifreeze}} = \frac{77816\,\text{g}}{188000\,\text{cm}^3} \approx 0.4145\,\text{g/cm}^3$

Rounding this to two decimal places gives:

$\text{Density}_{\text{antifreeze}} = 0.41\,\text{g/cm}^3$