What Do % V/V, % W/W and % W/V Mean?

When buying chemical products online, you will notice that the concentrations are either marked as v/v, w/w or w/v. These are common expressions, so what do they mean exactly?

% V/V

Volume concentration of a solution is expressed as % v/v, which stands for volume per volume. This is used when both chemicals in a solution are liquid.

For example, when 50ml of sulphuric acid is diluted with 50ml of water, there will be 50ml of sulphuric acid in a total volume of 100ml. Therefore, we would express the concentration of this solution as sulphuric acid 50% v/v.

% W/W

Weight concentration of a solution is expressed as % w/w. Like before, this stands for weight per weight. In this case, the volume of each chemical is disregarded and only the weight is used.

So, if the total mass of a 100g solution is made up of 30g hydrochloric acid in 70g of water, then we would express this as hydrochloric acid 30% w/w.

% W/V

Mass concentration of solution is expressed as % w/v for weight per volume. It can alternatively be abbreviated to m/v for mass per volume. This is used when a solid chemical is dissolved in a liquid.

If 1g of potassium iodide is used to make up a total volume of 100ml, then a 1% w/v solution of potassium iodide has been made.

Calculating Percentages

Each percentage type can be calculated by making small changes to the same method. For example, to find the % w/v of a solution the calculation is:

(Mass of Solute (g) / Volume of Solution (ml)) x 100

Therefore, to figure out the % w/v of a 100ml solution that is made up of 65g nitric acid, we would divide 65g by 100ml and then multiply the answer by 100. This tells us that there is a nitric acid solution of 65% w/v.

When working out the % v/v of a solution, the same method is used except it is the volume of the solute (ml) that is divided by the volume of the solution (ml). For example, a 1000ml solution that contains 450ml methanol has a methanol concentration of 45% v/v (450 / 1000 x 100).

Again, the method for calculating % w/w uses the same steps instead it is weight divided by weight.

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It is important to understand exactly what you’re purchasing. That’s why, at ReAgent, we have a skilled and dedicated team who you can speak with about any product enquiry you may have. Get in touch today to see how we can help.

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The blog on chemicals.co.uk and everything published on it is provided as an information resource only. The blog, its authors and affiliates accept no responsibility for any accident, injury or damage caused in part or directly from following the information provided on this website. We do not recommend using any chemical without first consulting the Material Safety Data Sheet which can be obtained from the manufacturer and following the safety advice and precautions on the product label. If you are in any doubt about health and safety issues please consult the Health & Safety Executive (HSE).

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