8 g sodium hydroxide is dissolved in water and final volume is made 200 mL. What is the molarity of the solution?
Answer and explanation
Correct answer: 1.00 M
Molarity is defined as moles of solute per litre of final solution. Sodium hydroxide has molar mass 40 g mol−1, so 8 g contains 8/40 = 0.20 mol. The final volume is 200 mL = 0.200 L. Therefore M = 0.20/0.200 = 1.00 mol L−1, or 1.00 M, so option C is correct. The volume of water before dissolution must not be used; the stated final solution volume is required.
Frequently asked questions
What is the correct answer to this question?
1.00 M
Why is this the correct answer?
Molarity is defined as moles of solute per litre of final solution. Sodium hydroxide has molar mass 40 g mol−1, so 8 g contains 8/40 = 0.20 mol. The final volume is 200 mL = 0.200 L. Therefore M = 0.20/0.200 = 1.00 mol L−1, or 1.00 M, so option C is correct. The volume of water before dissolution must not be used; the stated final solution volume is required.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Some Basic Concepts of Chemistry. Topic: Mole concept and molar mass.
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