Question

600 mL of 0.2 M NaCl can be prepared from 1 L of 0.3 M NaCl by
(a) Evaporating 400 mL of H₂0
(b) Evaporating 600 mL of H₂0
(c) Taking 400 mL solution and diluting it with water to make volume 600 mL
(d) Taking 800 mL solution then evaporating 200 mL H₂O​

Answer 1

Answer:

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Answer 2

600 of 0.2 M , NaCl can be prepared from 1L of 0.3 NaCl by evaporating 600 mL of H₂O.

what is molarity ?

molarity is the number of moles of solute per litre of solution.

i.e., Molarity = no of moles of solute/volume of solution in L

⇒ no of moles of solute = Molarity × volume of solution in L.

“No of moles of solute must be remained same if we evaporate or diluted the solution.”

i.e., M₁V₁ = M₂V₂

here let x mL of solution is evaporating so that solution becomes 600 mL of 0.2 M NaCl.

∵ V₁ = (1000 - x) mL , M₁ = 0.3 M , M₂ = 0.2 M and V₂ = 600 mL

⇒0.3 × (1000 - x) = 0.2 × 600

⇒1000 - x = 400

⇒x = 600 mL

Therefore the correct option is (b) evaporating 600 mL of H₂O.