A 50% sulfuric acid solution and a 20% sulfuric acid solution are mixed to prepare 12 litres of a 30% sulfuric acid solution. How much of each solution is required?

1. A

   2 litres of 50% + 10 litres of 20%

2. B

   3 litres of 50% + 9 litres of 20%

3. C

   4 litres of 50% + 8 litres of 20%

4. D

   5 litres of 50% + 7 litres of 20%

Appeared in: NORCET-11 Prelims

Explanation

• Set up equations for total volume and total acid content.
• Solve for x (50% solution) and y (20% solution) to match the target concentration.
• Only 4 litres of 50% and 8 litres of 20% yield exactly 3.6 litres of pure acid in 12 litres total.

Why Other Options Were Wrong

• Option A: 2 litres of 50% and 10 litres of 20% do not provide enough pure acid to reach 30% concentration in 12 litres.
• Option B: 3 litres of 50% and 9 litres of 20% result in less than 3.6 litres of pure acid, so the final concentration is below 30%.
• Option D: 5 litres of 50% and 7 litres of 20% result in more than 3.6 litres of pure acid, so the final concentration exceeds 30%.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mixing two solutions of different concentrations to achieve a target concentration and volume as background academic context rather than a clinical decision trigger.
• Nurses may need to prepare solutions of specific concentrations for cleaning, disinfection, or laboratory use.
• Accurate calculation prevents under- or over-concentration, which can affect efficacy and safety.
• What if? If the target concentration was 40%, more of the 50% solution and less of the 20% solution would be needed; calculation steps remain the same.

How to Approach the Question

• Identify the variables: let x and y be the volumes of each solution.
• Set up two equations: one for total volume, one for total pure substance.
• Substitute and solve the simultaneous equations.
• Check which option matches your calculated values.
• Use this method for any two-solution mixing problem.

Concept Tested & Keywords

• Concept Tested: Mixing two solutions of different concentrations to achieve a target concentration and volume
• Stem keywords: 50% sulfuric acid, 20% sulfuric acid, 12 litres, 30% sulfuric acid
• Lead-in keywords: How much, required

Question ID

QgPLFE0jynq7fXMymEeTPk

Copy ID

Reference Book

E6 Pharmacology Nurses Shanbhag 3e p. 54-56