Alcohol of mass 21g and density 0.7g cm-3 is mixed with 10g of water. Determine the density of the mixture [density of water = 1.0gcm-3]

The density of a substance is defined as its mass per unit volume. In this question, we are given the mass and density of alcohol and the mass and density of water. We can find the total volume of the mixture by adding the volumes of alcohol and water. The volume of alcohol is calculated as follows: Volume of alcohol = mass of alcohol/density of alcohol Volume of alcohol = 21g/0.7gcm^-3 Volume of alcohol = 30cm³ The volume of water is equal to its mass, which is 10g. The total volume of the mixture is: Total volume = volume of alcohol + volume of water Total volume = 30cm³ + 10cm³ Total volume = 40cm³ The mass of the mixture is the sum of the mass of alcohol and water: Mass of mixture = mass of alcohol + mass of water Mass of mixture = 21g + 10g Mass of mixture = 31g The density of the mixture is therefore: Density of mixture = mass of mixture/total volume Density of mixture = 31g/40cm³ Density of mixture = 0.775gcm^-3 Therefore, the density of the mixture is 0.775gcm^-3. Option A is the correct answer.