36.5 g of hydrogen chloride is dissolved in water to make 250 mL of solution. If the molar mass of hydrogen chloride is 36.5 g mol⁻¹, what is the molarity of the solution?
Answer and explanation
Correct answer: 4 mol L⁻¹
First find the amount of HCl: moles = mass/molar mass = 36.5/36.5 = 1.00 mol. Molarity is defined as moles of solute per litre of the final solution, not per litre of water used. The final volume is 250 mL = 0.250 L. Thus, molarity = 1.00/0.250 = 4.00 mol L⁻¹, making C correct. Options A and B do not account correctly for the quarter-litre volume.
Frequently asked questions
What is the correct answer to this question?
4 mol L⁻¹
Why is this the correct answer?
First find the amount of HCl: moles = mass/molar mass = 36.5/36.5 = 1.00 mol. Molarity is defined as moles of solute per litre of the final solution, not per litre of water used. The final volume is 250 mL = 0.250 L. Thus, molarity = 1.00/0.250 = 4.00 mol L⁻¹, making C correct. Options A and B do not account correctly for the quarter-litre volume.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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