Calculate the molarity of a solution prepared by dissolving 6.00 g of potassium nitrate ( $K N O_{3}$ , M = 101.1 g· $m o l^{- 1}$ ) in enough water to make 250.0 mL of solution at 25 °C.

easy 1 mark Class 12 · Chemistry · Solutions

Answer

M = 0.238 mol·

L^{- 1}

The correct answer is M = 0.238 mol· $L^{- 1}$ — Use the definition of molarity: M = n/V = 0.0594 mol / 0.2500 L = 0.2376 mol· $L^{- 1}$ , round to 0.238 mol· $L^{- 1}$ .

Step-by-step solution

Find the amount of substance: n = mass/M = 6.00 g / 101.1 g· $m o l^{- 1}$ = 0.0594 mol.
Convert the solution volume to litres: V = 250.0 mL = 0.2500 L.
Use the definition of molarity: M = n/V = 0.0594 mol / 0.2500 L = 0.2376 mol· $L^{- 1}$ , round to 0.238 mol· $L^{- 1}$ .

Common mistake: Forgetting to convert mL to L before using M = n/V

Concept tested: Molarity calculation

Published 13 September 2026 · Last updated 16 September 2026 · How this solution was prepared and checked

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Calculate the molarity of a solution prepared by dissolving 6.00 g of potassium nitrate (KNO3​, M = 101.1 g·mol−1) in enough water to make 250.0 mL of solution at 25 °C.

Step-by-step solution

Calculate the molarity of a solution prepared by dissolving 6.00 g of potassium nitrate ( $K N O_{3}$ , M = 101.1 g· $m o l^{- 1}$ ) in enough water to make 250.0 mL of solution at 25 °C.