Dilution Factor : It indicate what quantity of volume is there in your solution in comparison to the original solution.
It is also known by the name of dilution ratio.
The answer would be the 4% of the solution needed before having the final concentrations of the solution to the 50% of serial dilution with the initial concentration.
Here , 50 % serial dilution,
Initial concentration = 10 %
Final concentrations =2.5 %
v1*c1 = v2*c2
v2 = v1*c1/ c2
Putting values we get 2%
Converting into percentage we get 4 %
In conclusion 4% dilution we have to make before having final concentration.
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