You add 400ml of pure water to 600ml of a 35% acid solution. What is the concentration of acid in the resulting mixture

To find the concentration of acid in the resulting mixture, we need to calculate the amount of acid in the 35% acid solution and the amount of acid in the pure water, and then find the total amount of acid in the mixture.

Step 1: Calculate the amount of acid in the 35% acid solution.
The 35% acid solution has a concentration of 35%, which means that 35% of the solution is acid. We can calculate the amount of acid in the 35% acid solution using the formula:

Amount of acid in solution = Concentration of acid × Volume of solution

The volume of the 35% acid solution is 600 ml. Therefore:

Amount of acid in the 35% acid solution = 35% × 600 ml = 0.35 × 600 ml = 210 ml

So, the 35% acid solution contains 210 ml of acid.

Step 2: Calculate the amount of acid in the pure water.
Pure water does not contain any acid, so the amount of acid in the pure water is 0 ml.

Step 3: Find the total amount of acid in the mixture.
To find the total amount of acid in the mixture, we add the amount of acid in the 35% acid solution and the amount of acid in the pure water:

Total amount of acid in the mixture = Amount of acid in the 35% acid solution + Amount of acid in the pure water
Total amount of acid in the mixture = 210 ml + 0 ml
Total amount of acid in the mixture = 210 ml

Step 4: Calculate the concentration of acid in the resulting mixture.
Finally, we need to find the concentration of acid in the resulting mixture. The volume of the resulting mixture is the sum of the volume of the 35% acid solution and the volume of the pure water:

Volume of resulting mixture = Volume of 35% acid solution + Volume of pure water
Volume of resulting mixture = 600 ml + 400 ml
Volume of resulting mixture = 1000 ml

The concentration of acid in the resulting mixture can be calculated using the formula:

Concentration of acid in resulting mixture = Total amount of acid in mixture / Volume of resulting mixture
Concentration of acid in resulting mixture = 210 ml / 1000 ml

Concentration of acid in resulting mixture = 0.21

Answer: The concentration of acid in the resulting mixture is 0.21 (or 21%).