200 cm3 of water would be required to be added to the starting solution in order to give the correct concentration.
The desired concentration can be calculated using the dilution equation:
In this case, M1 = 0.5, V1 = 50 cm3 = 0.05 dm3, M2 - 0.1, V2= ?
V2 = M1V1/M2
= 0.5 x 0.05/0.1
= 0.25 dm3
= 250 cm3
Since the final volume is 250cm3 and the initial volume is 50 cm3, it means that 200 cm3 of water is required to be added to the acid in order to arrive at the desired (0.1 M) concentration.
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