If 400 ml of a 20% w/v solution were diluted to 2 l, what would be the final percentage strength?

"4" will be the final percentage strength.

According to the question,

20% solution with 400 mL has 20% × 400 mL of solute

then,

→

hence,

The concentration will be:

→

or,

            (%)

Thus the answer above is right.

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4%

Step-by-step explanation:

A 20% solution with a total volume of 400 mL has 20% * 400 mL of solute.

20% * 400 mL = 80 mL

When you dilute the solution to 2 L, you introduce additional water, but no additional solute, so now you have the same 80 mL of solute in 2 L of total solution.

The concentration is:

(80 mL)/(2 L) = (80 mL)/(2000 mL) = 0.04

As a percent it is:

0.04 * 100% = 4%

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