Question

A chemist prepares a mixture of hexane and toluene Add a temperature of 18.0 Celsius. He measures out 411. mL I’ve hexane and mixes it with 1.49 L. He measures a volume of the solution after it is well mix and find that it is 2.00 L. The density of the hexane is 0.66 g/mL and a density of the toluene is 0.87 g/mL. Calculate the volume percentage of hexane in the solution. Be sure you answer has the right number of significant digits.? % (v/v)

Answer 1

Step 1 - Discovering the density of hexane in the new solution

We know the density is the mass divided by the volume:

`d=(m)/(V)`

To find the new density of hexane, i.e., the density of hexane in the mixture, we just have to divide its mass by the total volume of the solution. Let's divide it in two steps:

a) We will first calculate the mass of hexane that was add in the mixture. We'll use the density of pure hexane:

`d=(m)/(V)\to m=V* d`

The density of pure hexane is 0.66 g/ml and the volume that was added is 411 ml. Therefore:

`m=411*0.66=271.26\text{ g}`

b) Now, we'll proceed to find the density of hexane in the mixture. We just have to divide its mass (271.26 g) by the total volume of the mixture:

`V_{\text{total}}=2\text{ L = 2000 ml}`

The density will be thus:

`d=(271.26)/(2000)=0.13\text{ g/ml}`

Step 2 - Using the new density of hexane to calculate its volume percentage

Now that we have calculated the new density of hexane, we can find how much volume it occupies in the mixture. Let's divide the mass of hexane (271.26 g) by the new density: