dilution of hydrogen peroxide

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Reply 20

is da answer 7.4 cm3 of h202 required

Reply 21

this is what ive done can u check it

0.02 x 25/1000= 0.0005 moles of KMnO4
0.0005 x 5 /2 = 0.00125 moles of h202
0.00125/2 = 0.000625 moles of 02
1 moles of gas is 24dm3 so 0.000625 moles is 15cm3
because its 20 volume therefore 0.75cm3 of h202 produces 15cm3 of 02
so 0.75 x 10 =7.5cm3 of h202 will produce 150cm3 of 02
therefore i would dilue it to 250cm3 with 7.5cm3 of h202

concentration of h202?

0.00125= moles of h202 in 25cm3
x 10 = 0.0125 moles of h202 in 250cm3
concentration= 0.0125/7.5 x 1000 = 1.67mol/dm3

Reply 22

snake

also dis means my titre of KMnO4 should be 25cm3

Reply 23

snake

can some 1 check da above plz

Reply 24

silent ninja

7cm3 is about right. So make it up to 250cm3 with 7cm3 of the original. Hydrogen Peroxide isn't dead on 20 vol and the whole point of the titration against standard KMnO4 is to find the actual concentration.

Reply 25

charco

Study Forum Helper

you shouldn't choose 7cm3 because it is not easily measured with standard apparatus. Far better to double the volume of the solution and use 15cm3 from a pipette.

Reply 26

snake

so is the concentration right, it is 1.67mol/dm3 isnt it

you know part b i jus plotted mass of 02 produced against time and did half lifes. do we just make up our results