You have a stock solution of hno3 with a concentration of 4.5x10-4 m. however, you need 275 ml of a 2.50x10-5 m solution. how much of the stock solution will you need?

27.5 mL.

Explanation:

We have the rule that the no. of millimoles of the solution before dilution is equal to the no. of millimoles after dilution.

(MV)before dilution = (MV)after dilution,

M before dilution = 4.5 x 10⁻⁴ M, V before dilution = ??? mL,

M after dilution = 2.50 x 10⁻⁵ M, V after dilution = 275.0 mL.

∴ V before dilution = (MV)after dilution / M before dilution = (2.50 x 10⁻⁵ M)(275.0 mL) / (2.50 x 10⁻⁵ M) = 27.5 mL.

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