3. You receive an order for 30 mL of 3% boric acid solution. The pharmacy has in stock a 1% and 5% boric acid solution in stock
.01 x + .05(30 - x) = .03 (30)
or just use the 5% solution and add water. Since 3% is 3/5 of 5%, just use 3/5 of the 30mL and fill the rest with water:
18 mL 5% + 12 mL water
Or, for a much slower method, pour some 1% solution in a beaker and let it evaporate. Since 1% is 1/3 as much as 3%, start out with 3 times the volume. Let 90mL evaporate till only 30mL is left. Then it will be 3%.
Just sayin' ...
To prepare a 30 mL of 3% boric acid solution, you can use a combination of the 1% and 5% boric acid solutions available in the pharmacy. Here's how you can calculate the amount of each solution you'll need:
Let's assume:
- x mL of the 1% boric acid solution
- y mL of the 5% boric acid solution
We can establish two equations based on the given information:
Equation 1: The total volume required is 30 mL
x + y = 30
Equation 2: The percentage of boric acid in the final solution is 3%
(0.01x + 0.05y) / 30 = 0.03
Now, you can solve these simultaneous equations to find the values for x and y.
First, rearrange Equation 1 to express x in terms of y:
x = 30 - y
Substitute this value of x into Equation 2:
(0.01(30-y) + 0.05y) / 30 = 0.03
Let's simplify the equation step-by-step:
(0.01(30-y) + 0.05y) = 0.03 * 30
(0.3 - 0.01y + 0.05y) = 0.9
0.3 + 0.04y = 0.9
0.04y = 0.9 - 0.3
0.04y = 0.6
y = 0.6 / 0.04
y = 15
Therefore, you would need 15 mL of the 5% boric acid solution.
Now, substitute the value of y back into Equation 1 to find x:
x + 15 = 30
x = 30 - 15
x = 15
Therefore, you would need 15 mL of the 1% boric acid solution.
To summarize, to make a 30 mL of 3% boric acid solution, you would need to mix 15 mL of the 1% boric acid solution and 15 mL of the 5% boric acid solution.