Multiple choice

How much water must be added to 70 liters of 50% solution of boric acid to reduce it to a 20 percent solution?

  1. 95 liters

  2. 100 liters

  3. 105 liters

  4. 115 liters
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Starting with 70 liters of 50% boric acid means 35 liters of pure acid. For a 20% solution, 35 liters must be 20% of total volume. So total volume = 35/0.20 = 175 liters. Water to add = 175 - 70 = 105 liters. Check: 35/(70+105) = 35/175 = 0.20 = 20%.

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