# Homework Help: Density of a mixture

1. Dec 3, 2011

### 2slowtogofast

1. The problem statement, all variables and given/known data
I know the density of a mixture of water and glycol. I will call that dmix. I need to find the percentage of water and the percentage of glycol in the mixture. The only other thing I know is the temp.

2. Relevant equations

d=m/v

3. The attempt at a solution

What am unsure of is the following true

Let x = %glycol
Let 1-x = %water

dmix = (x)dglycol + (1-x)dwater

2. Dec 3, 2011

### LawrenceC

Yes, it's true. Since you have the temperature of the mixture, you can look up the densities of each component at the appropriate temperature. Then proceed.

3. Dec 3, 2011

good. Thanks

4. Dec 3, 2011

### Staff: Mentor

It is NOT true. Volumes are not additive.

For some substances - ethylene glycol included - it works quite good, but it doesn't in general. SO each time you should check if the density vs composition curve is linear - or not.

5. Dec 3, 2011

### 2slowtogofast

Ok I though it might not be true. So is there another way this calc can be done with the given info?

6. Dec 3, 2011

### Staff: Mentor

Density table is the only sure way to go. That's how my works. Unfortunately, density table for ethylene glycol that is built into the program is limited to 60% w/w. It can be easily extended if you can find a better density table.