Multiple choice

A container contains 20 L mixture in which there is 10\% sulphuric acid. Find the quantity of sulphuric acid to be added in it to make the solution to contain 25\% sulphuric acid.

  1. $3$
  2. $4$
  3. $2$
  4. $5$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In 20 L mixture with 10% acid, acid = 20 × 0.10 = 2 L. Let x liters of pure acid be added. New volume = 20 + x, new acid = 2 + x. Required: (2 + x)/(20 + x) = 0.25. Solving: 2 + x = 0.25(20 + x) = 5 + 0.25x, so 0.75x = 3 and x = 4 L.

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