Dilution: how much water to add
How much water must be added to 50 mL of 2 M NaCl to make a 0.5 M solution?
Answer B: explanation for every choice
A
This inverts the ratio in M₁V₁ = M₂V₂.
B
Correct. V₂ = M₁V₁/M₂ = (2)(50)/0.5 = 200 mL, so add 200 − 50 = 150 mL.
C
200 mL is the final total volume, not the water added.
D
This adds the final volume to the original 50 mL.
TakeawayM₁V₁ = M₂V₂ gives the final volume. Subtract the starting volume to get the water added.
Equation usedMolarity and dilution
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