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**What are percentage solutions?**

A percentage solution is an amount or volume of something per 100 ml or 100 g of a solution. It is as simple as that. It is a percentage.

**Why are they used?**

Percentage solutions are a convenient and easy way to record solution concentrations. One advantage is that you don’t need to know anything about the compound in terms of molecular weight; all you need is the percentage of the required solution.

**Why are there three types of percentage solutions?**

This is slightly difficult to explain. However, there are three types of percentage solutions:

- Percentage weight by volume (w/v)
- Percentage volume by volume (v/v)
- Percentage weight by weight (w/w)

*percentage weight by volume (w/v)*is the number of grams of compound per 100 ml of solution. This type of percentage solution is used when describing the amount of powder in a solution. For example, 5 g of powder made up to a final volume of 100 ml would be a 5% (w/v) solution. Likewise, 2.5 g of powder made up to 50 ml would also be a 5% (w/v) solution, as you would have 5 g in 100 ml.

The

*percentage volume by volume (v/v)*is the number of ml of some liquid per 100 ml of the solution. This type of percentage solution is usually used to describe a solution made by mixing two liquids. For example, 5 ml of a liquid made up to a final volume of 100 ml would be a 5% (v/v) solution. Likewise, 2.5 ml of a liquid made up to 50 ml would also be a 5% (v/v) solution, as you would have 5 ml in 100 ml.

Finally, the

*percentage weight by weight (w/w)*. This one is more difficult to understand, but the principles, as explained above, are still valid. A percentage weight by weight (w/w) solution can be the weight of a powder or a liquid made up in a solution to the final weight of the solution. So, for example, 5 g of a powder (or a liquid) made up in a solution with a final weight of 100 g would be a 5% (w/w) solution. Likewise, 2.5 g of a liquid or powder made up to give a solution that weighed 50 g would also be a 5% (w/w) solution, as you would have 5 g of the powder or liquid in 100 g of a solution.

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