Question

How many grams of a drug substance should be added to 1800 mL of water to make a 10% ww solution?

Answer 1

To make a 10% ww solution with a total volume of 1800 mL of water, you would need to weigh out 180 g of the drug substance and mix it with the water, ensuring that the final combined weight of solute and solvent is 1800 g.

Step-by-step explanation:

To make a 10% weight/weight (ww) solution, you need to know the weight of the solute and the weight of the solution. For a 10% ww solution, the weight of the drug substance will be 10% of the total weight of the solution. If you want the total solution to weigh 1800 g (since 1 mL of water is approximately equivalent to 1 g, and you have 1800 mL of water), you'll need to add 180 g of the drug substance to 1620 g of water (because you have to subtract the weight of the drug substance from the total weight of the solution to find the weight of the water that needs to be added).

The process would include weighing out 180 g of the drug substance and adding it to the water to reach a combined total weight of 1800 g. This is similar to the example where 150 g of NaCl is added to 2850 g of water to make a 3000 g solution (again subtracting the solute's mass from the total solution's mass to find the necessary mass of water).

Answer 2

To make a 10% (w/w) solution, you need to add 10 grams of the drug substance for every 100 grams of the solution.

In this case, you want to prepare a solution with a total mass of 1800 grams (since 1800 mL of water is approximately 1800 grams, as 1 mL of water is roughly equivalent to 1 gram).

So, to calculate the amount of the drug substance needed:

Amount of drug substance (in grams) = (10% of the total mass) = 0.10 * 1800 grams

Amount of drug substance = 180 grams

You need to add 180 grams of the drug substance to 1800 mL of water to make a 10% (w/w) solution.