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Tricky Chemistry Question

5·0 cm3 of a solution of hydrochloric acid was
diluted to exactly 250 cm3 with water. The
pH of this diluted solution was 2·00.

The concentration of the original undiluted
solution, in mol l–1, was

A 2·0 × 10–2
B 4·0 × 10–2
C 4·0 × 10–1
D 5·0 × 10–1.

I just cant solve this problem, can someone please explain also, so i can understand? :smile:

Reply 1

charco

Study Forum Helper

Original post by flyingpanda786

Dilution involves increasing the volume without affecting the moles present.

The effect of dilution is inversely proportional to the dilution factor.

Here you have a dilution factor of 5 to 250, or put it another way, 1 to 50

The hydrogen ion concentration will decrease by a factor of 1/50

pH is a log scale and a decrease in hydrogen ion concentration by a factor of 10 causes an increase in pH of 1.

You should be able to apply the above to find the answer ...