# How to find quality?

If a mixture has a volume of 1,276 cubic cm and a mass of 100 grams and the vapor portion has a specific volume of 0.16 cubic meters per kg and the liquid portion has a specific volume of 0.0007 cubic meters per kg.

What is the quality of the mixture?

Using (v-vg)/(vg-vf) i keep getting -0.96. the correct answer is 0.07571, but I don't know ho to get to that.

### 1 Answer

- Anonymous9 months agoFavourite answer
You can do a rigorous mass balance (volume of vapor * density of vapor + volume of liquid * density of liquid = 100 g) but the volume of liquid can likely be neglected.

1276 cm^3 = 0.001276 m^3

0.001276 m^3 / (0.16 m^3/kg) = 0.007975 kg = 7.975 g

Quality = 7.975 g / 100 g = 0.0798

We can clean this up a bit with another iteration since the liquid volume would be the difference.

Mass of liquid = 100 g - 7.975 g = 92.83 g. Volume of liquid = 64.9 cm^3. That leaves 1276 cm^3 - 64.9 cm^3 = 1211 cm^3 with a mass of 7.56 g of vapor.

7.56 g / 100 g = 0.0756, much closer to your number.

Post your work and I can take a look at it.

< What is the quality of the mixture? >

Remember that the quality of a mixture is just the mass of vapor / total mass.

0% is no vapor. 100% is all vapor, no liquid.

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