To solve this problem, we can break it down into two parts.

Part (a): How many milliliters of acid are in the resulting mixture?

1. Calculate the amount of acid in the 75 milliliters of 15% solution:

   $\text{Amount of acid} = 75 \, \text{ml} \times \frac{15}{100} = 11.25 \, \text{ml}$

2. Calculate the amount of acid in the 175 milliliters of 75% solution:

   $\text{Amount of acid} = 175 \, \text{ml} \times \frac{75}{100} = 131.25 \, \text{ml}$

3. Add these two amounts together to get the total amount of acid in the mixture:

   $\text{Total acid} = 11.25 \, \text{ml} + 131.25 \, \text{ml} = 142.5 \, \text{ml}$

Part (b): What percentage of the resulting mixture is acid?

1. Calculate the total volume of the mixture:

   $\text{Total volume} = 75 \, \text{ml} + 175 \, \text{ml} = 250 \, \text{ml}$

2. Calculate the percentage of acid in the mixture:

   $\text{Percentage of acid} = \left(\frac{142.5 \, \text{ml}}{250 \, \text{ml}}\right) \times 100 = 57\%$

Final Answers:

• (a) There are 142.5 milliliters of acid in the resulting mixture.
• (b) The resulting mixture is 57% acid.

Do you want details or have any questions?

Here are 5 related questions for further practice:

1. If the chemist added 50 milliliters of water to the final mixture, what would the new percentage of acid be?
2. What would happen if the chemist used 100 milliliters of the 75% acid solution instead of 175 milliliters?
3. If the chemist wanted a final solution that is 50% acid, how much of the original 15% acid solution should they mix with the 175 milliliters of 75% acid solution?
4. What is the difference in acid concentration if the chemist mixes the two solutions in equal volumes instead of the given proportions?
5. How would the percentage change if the chemist added another 75 milliliters of the 15% acid solution to the final mixture?

Tip: When dealing with mixtures, always remember to account for both the volume and concentration of each component to accurately determine the final mixture's properties.