Post-UTME Chemistry 2005 Objective — Question 20
Question 20 of 27 from the Post-UTME Screening (Post-UTME) Chemistry 2005 Objective paper, with the correct answer and a full explanation.
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15g of water dissolves 3.5g of sodium chloride at 25 degrees C. What is the solubility of the sodium chloride at that temperature? [Na=23, Cl=35.5]
- A. 0.4mol/dm^3
- B. 4.0mol/dm^3Correct
- C. 40mol/dm^3
- D. 400mol/dm^3
Explanation
Solubility = 3.5/15 x 100 = 23.3g per 100g water. In 0.1dm^3 (approx 100g water), moles = 23.3/58.5 = 0.399mol, giving a concentration of about 4.0mol/dm^3.
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