IMAT 2016 Q41 [Dissolving In Water]

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Which of the following substances will form an alkaline solution when dissolved in water?

  1. Na_2CO_3
  2. NaCl
  3. NaHSO_4

A. 1, 2 and 3
B. 1 only
C. 1 and 2 only
D. 2 and 3 only
E. 1 and 3 only

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To answer this question, it is important to understand the difference between an alkaline substance and an acidic substance. An alkaline substance is one that produces hydroxide ions (OH-) when it is dissolved in water. An acidic substance, on the other hand, produces hydrogen ions (H+) when it is dissolved in water.

The substances listed in the question are all soluble in water, which means that they will dissociate (or break apart) into their individual ions when they are dissolved in water. Based on this information, we can determine which of the substances will form an alkaline solution when dissolved in water.

Na2CO3: When sodium carbonate (Na2CO3) is dissolved in water, it dissociates into sodium ions (Na+) and carbonate ions (CO3-). The carbonate ions will react with water to produce hydroxide ions (OH-), which makes the solution alkaline. Therefore, Na2CO3 will form an alkaline solution when dissolved in water.

NaCl: When sodium chloride (NaCl) is dissolved in water, it dissociates into sodium ions (Na+) and chloride ions (Cl-). The chloride ions do not react with water, so the solution will not be alkaline or acidic. Therefore, NaCl will not form an alkaline solution when dissolved in water.

NaHSO4: When sodium hydrogen sulfate (NaHSO4) is dissolved in water, it dissociates into sodium ions (Na+), hydrogen ions (H+), and sulfate ions (SO4-). The hydrogen ions will react with water to produce hydronium ions (H3O+), which makes the solution acidic. Therefore, NaHSO4 will not form an alkaline solution when dissolved in water.

Based on this information, the correct answer is option B: “1 only”. Only sodium carbonate (Na2CO3) will form an alkaline solution when dissolved in water.

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Can’t think this way?

  1. Produce 2NaOH and H2CO3 which is strong base and weak acid>>basic solution
  2. Produce HCl and NaOH which is strong acid and strong base>>not basic
  3. Produce H2SO4 and NaOH which is also strong acid and strong base>>not basic

In conclusion, answer is only 1.

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