[inno2]

am doing IB but things are really difficult with higher chemistry like percentage purity.
could someone help me with this qn.

the sample of Lithium hydroxide of mass 0.62g. it is dissolved in water to make a solution of 250cm₃. 25cm3 of the solution was titrated and 21.25cm3 of HCl of .10M were required. if LiOH is contaminated with LiCl. calculate the mass of LiOH and hence the percentage purity

[Dan]

1. Write a balanced equation for the reaction of LiOH and HCl
2. Determine the amount (moles) of HCl required
3. Using your balanced equation, determine the amount (moles) of LiOH in the sample, we will call that number X moles
4. Determine the theoretical mass of X mol LiOH
5. How does this mass compare to the mass of the sample used? What is the mass of LiCl in the sample?
6. Determine percentage purity

[n0m0r3l0v3_0k]

LiOH + HCl → LiCl + H2O
nHCl =  21.25/1000  x 0.1= 2.125x10-3 ==> 25 cm3 of LiOH solution contain 2.125x10-3 moles LiOH
==> 250 cm3 of LiOH solution contain 2.125x10-2 moles LiOH
==> % purity = 0.02125/(0.62/24) x 100%=82.258%