Physics 2022 JAMB Past Questions - Question 12: If 21g of alcohol of density 0.7gcm-³ is mixed with 10g of water, what would be the density of the resulting mixture?

Correct Answer

B

Explanation

To find the density of the resulting mixture, we can use the formula:

\[ \text{Density} = \frac{\text{Total mass}}{\text{Total volume}} \]

First, let's find the total volume of the mixture. The volume of alcohol can be calculated using the formula:

\[ \text{Volume of alcohol} = \frac{\text{Mass of alcohol}}{\text{Density of alcohol}} \]

So, the volume of alcohol is:

\[ \text{Volume of alcohol} = \frac{21g}{0.7g/cm³} = 30cm³ \]

The volume of water is simply its mass, as the density of water is 1g/cm³.

So, the total volume of the mixture is:

\[ \text{Total volume} = \text{Volume of alcohol} + \text{Volume of water} = 30cm³ + 10cm³ = 40cm³ \]

Now, we can find the total mass of the mixture:

\[ \text{Total mass} = \text{Mass of alcohol} + \text{Mass of water} = 21g + 10g = 31g \]

Finally, we can calculate the density of the resulting mixture:

\[ \text{Density} = \frac{31g}{40cm³} = 0.775g/cm³ \]

So, the density of the resulting mixture would be 0.775g/cm³.