1.

Bleaching powder and bleach solution are produced on a large scale and used in several household products. The effectiveness of bleach solution is often measured by iodometry. 25 mL of household bleach solution was mixed with 30 mL of 0.50 M KI and 10 mL of 4 N acetic acid. In the titration of the liberated iodine, 48 mL of 0.25 N Na_(2)S_(2)O_(3) was used to reach the end point. The molarity of the household bleach solution is :

Answer»

0.48 M
0.96 M
0.24 M
0.024 M

Solution :Hydrogen peroxide is a household bleach.
`underset((25 mL))(H_(2)O_(2))+underset(0.5 M 30 mL)(2I^(-))+underset(4 N 10 mL)(2H^(+)) to I_(2)+2H_(2)O`
`I_(2)+underset(0.25 N 48 mL)(2Na_(2)S_(2)O_(3)) to 2 NaI+Na_(2)S_(4)O_(6)`
Normality and molarity of `CH_(3)COOH(H^(+)) " and" Na_(2)S_(2)O_(3)` will be equal.
NUMBER of moles of `I_(2)=(1)/(2)xx " Number of moles of " Na_(2)S_(2)O_(3)`
`=(1)/(2)[(MV)/(1000)]=(1)/(2)[(0.25xx48)/(1000)]=6XX10^(-3)`
Number of moles of `H_(2)O_(2)`= Number of moles of `I_(2)`
`=6xx10^(-3)`
Molarity of `H_(2)O_(2)=(n_(H_(2)O_(2)))/(V)xx1000`
`=(6xx10^(-3))/(25)xx1000`
=0.24


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