%v/v, %w/w and %w/v terms is designed to express the %age of total volume of the solution either in v/v, w/w and w/v. Let’s discuss all these terms one by one.
Differentiate between %v/v, %w/w and %w/v
% v/v
The volume concentration is expressed as % v/v, which stands for volume by volume. This is used when both chemicals in a solution are liquid state. For example, when 60 ml of sulphuric acid is diluted with 40 ml of water, there will be 60 ml of sulphuric acid in a total volume of 100 ml. Therefore, we would express the concentration of this solution as sulphuric acid 60% v/v.
or, In other words, it represents the volume of solute (the substance being dissolved) as a percentage of the total volume of the solution. For example, a 5% v/v solution would contain 5 milliliters of solute in 100 milliliters of solution.
% w/w
The weight concentration of a solution is expressed as % w/w. This stands for weight by weight. In this case, the volume of each chemical is ignored and only the weight is used. So, if the total mass of a 100 g solution is made up of 20 g HCL in 80 g of water, then we would express this as HCL (hydrochloric acid) 20% w/w.
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% w/v
The mass concentration of a solution is expressed as % w/v for weight by volume. It can alternatively be shortened to m/v for mass per volume. This is used when a solid chemical is dissolved in a liquid.
If 2 g of potassium iodide is used to make up a total volume of 100 ml. then a 2% 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 % weight/volume 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 100 ml solution that is made up of 60 g sulphuric acid, we would divide 60 g by 100 ml and then multiply the answer by 100. This tells us that there is a sulphuric acid solution of 60% w/v.
Example: What is the % weight/volume of a solution that has 7.5 g of sodium chloride diluted to 100 mL with deionized water? By definition, a percent weight/volume solution is the measure of weight per 100 mL.
7.5 g/100 mL = 7.5%
You can calculate this value as well: X % = 7.5 g NaC1/100 mL of solution X/100 = 7.5/100 Cross multiplying, 100 X = 750 X = 7.5% w/v
When working out the % volume/volume of a solution, the same method is used besides for the volume of the solute (ml) divided by the volume of the solution (ml). For example, a 1000m1 solution that contains 450m1 methanol has a methanol concentration of 45% v/v (450 / 1000 x 100).
The method for calculating % w/w uses the same steps instead it is weight divided by weight.
RPh. Naresh is a registered Pharmacist having studied pharmacy at PGIMS. he is a passionate blogger and writes topics around the pharma and pharmaceutical industries. Our blog also Provide all solution to get job information in the Pharmaceutical industry. The platform also helps people to prepare for their interviews by posting important interview questions.
