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A student dissolves 0.3 g of sodium hydroxide (NaOH, molar mass 40 g mol⁻¹) in 300 mL of water. What is the molarity of the solution?

easy 1 mark Class 7 · Science · Acids, Bases and Salts
Answer
0.025 M

The correct answer is 0.025 M — Calculate molarity: 0.0075 mol ÷ 0.300 L = 0.025 mol L⁻¹ = 0.025 M.

Step-by-step solution

  1. Determine moles of NaOH: 0.3 g ÷ 40 g mol⁻¹ = 0.0075 mol.
  2. Convert volume of solution to liters: 300 mL = 0.300 L.
  3. Calculate molarity: 0.0075 mol ÷ 0.300 L = 0.025 mol L⁻¹ = 0.025 M.
Common mistake: using grams instead of moles in the formula

Concept tested: Molarity calculation

Published · How this solution was prepared and checked

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