what quantity x of a 65% acid solution must be mixed with a 20% solution to produce 300 mL of a 45% solution

Your school subject is not college.

To find the quantity of the 65% acid solution needed, let's break down the problem step by step:

Step 1: Define the variables:
Let's assume that the quantity of the 65% acid solution to be added is 'x' mL.

Step 2: Calculate the quantity of the 20% solution:
Since the total volume of the mixture is 300 mL, the quantity of the 20% solution can be calculated as (300 - x) mL.

Step 3: Set up the equation based on the acid concentration:
Since we want to produce a 300 mL mixture with a 45% acid concentration, we can set up the equation as follows:

0.65x + 0.20(300 - x) = 0.45(300)

Step 4: Solve the equation:
Now, let's solve the equation to find the value of 'x'.

0.65x + 0.20(300 - x) = 0.45(300)

0.65x + 60 - 0.20x = 135

0.45x = 135 - 60

0.45x = 75

x = 75 / 0.45

x ≈ 166.67 mL (rounded to two decimal places)

So, approximately 166.67 mL of the 65% acid solution needs to be mixed with 133.33 mL of the 20% solution to produce 300 mL of a 45% solution.