How many grams of a drug should be added to 180 ml of water to make a 15% (w/w) solution?
My answer:
0.15 = (x/180)
x= 27 gm
looks good
To find out how many grams of the drug should be added to 180 ml of water to make a 15% (w/w) solution, you can use the formula:
% (w/w) = (grams of solute / grams of solution) * 100
In this case, the grams of solute is what we want to find, and the grams of solution is the sum of the grams of solute and the grams of solvent (water in this case).
Let's assume x represents the grams of the drug.
First, convert the 15% concentration to a decimal by dividing it by 100:
15% = 0.15.
Next, set up an equation using the formula:
0.15 = (x / (x + 180)).
Multiply both sides of the equation by (x + 180) to isolate x:
0.15 * (x + 180) = x.
Distribute 0.15:
0.15x + 27 = x.
Subtract 0.15x from both sides:
27 = 0.85x.
To solve for x, divide both sides by 0.85:
x = 27 / 0.85.
Evaluating this expression, you find that x is approximately 31.76 grams.
Therefore, approximately 31.76 grams of the drug should be added to 180 ml of water to make a 15% (w/w) solution.