Question 35

The concentration of salicylic acid in the final product is 7.50%.

To determine the concentration of salicylic acid in the final product, we can use the formula: concentration (%) = (mass of solute / total mass of solution) × 100. In this case, the total mass of the solution is the mass of salicylic acid plus the mass of the petrolatum used in the jars.

A) 6.25%

This option is incorrect because it underestimates the concentration of salicylic acid. To achieve a concentration of 6.25%, the ratio of salicylic acid to the total mass of the solution would need to reflect a lower amount of salicylic acid relative to the total mass, which does not align with the calculated value based on the given mass of salicylic acid.

B) 7.50%

This option is correct as it accurately represents the concentration of salicylic acid when calculated. With 288 g of salicylic acid used in a total mixture that includes the mass of the petrolatum, the concentration calculated aligns perfectly with this value, confirming its correctness.

C) 15%

This option is incorrect, as a concentration of 15% would imply a much higher proportion of salicylic acid relative to the total mass of the preparation. The calculations show that the actual concentration is lower than this figure, making it an inaccurate choice.

D) 20%

This option is also incorrect because a concentration of 20% would require an even greater amount of salicylic acid compared to the total mass of the solution. Given the data available, this concentration does not match the calculated results and thus is not a viable answer.

Conclusion

The correct answer is 7.50% as it accurately reflects the ratio of salicylic acid to the total mass of the mixture based on the provided information. All other options fail to match the calculated concentration, proving them incorrect. The process of calculation confirms that Option B is indeed the only viable answer based on the data given.