[akxls]

Materials
hydrogen peroxide solution (6.0%w/v) - commercial
2.00 mol/L sulfuric acid solution
150mL standardized 0.02 mol/L permanganate solution

** I wasn't sure if I'm posting in the right section but I'm doing this in high school right now so it seemed appropriate but it could go under Analytical Chemistry too so sorry in advance if it should be there specifically..


Situation:

a 20mL sample of the diluted H2O2 solution (diluted 1:50) with 10mL of dilute sulfuric acid

- determine the concentration of the diluted H2O2 in mol/L and undiluted solution in mol/L and %w/v

- determine the theoretical titre value

So I have attempted the problem..
H2O2
c = ?
v = 20mL
6% w/v

6x10 = 60gL^-1
divide by the molar mass

gives 60/(1.008+1.008+16+16)

concentration = 1.763875823
since it was diluted i should divide this value by 50? (1:50)

= 0.03527751646

** so the undilute conc is 1.8? and the dilute conc is 0.04?

moles in h2o2 = concentration x volume
so 0.03527751646 x 20 x 10^-3

= 7.055 x 10^-4 moles of h202
* I am not sure if I am doing this correctly with molar ratio and was hoping for someone to correct me here*

mno4-
c = 0.02 mol/L
v = ?
2:5

7.055 x 10^-4 moles in h2o2 x 5

= 3.53 x 10^-3

divide by 2

therefore moles in mno4- = 1.76 x 10^-3



volume = moles / concentration

so it should be 1.76 x 10^-3 / 0.02?

therefore the theoretical value is 0.0881937116 L
x 10^3

should give the answer in mL

but I got 88.19mL?!

I'm confused on where I went wrong..
Thankyou for your time.

[Borek]

7.055 x 10^-4 moles in h2o2 x 5

= 3.53 x 10^-3

divide by 2

therefore moles in mno4- = 1.76 x 10^-3

You got it reversed - not 5/2 but 2/5.

[akxls]

thanks. I worked it out.