[Lonestar]

hi guys, i'm new here, in 3rd year chemistry at uni in melbourne australia,

i've run into a lil problem here which was wondering if anyone could help, the question is

write out a balance equation for the oxidation of I- by OCL- to form I₂ and Cl- and OH-

start of the year so i'm a bit foggy, thanks if anyone could help

i have a idea, not sure if its right

OCL- + 4H+ + 2e- ==> Cl ₂ + 2H₂O for the half equation and then get Cl and H₂O into 2 more equations?

[LQ43]

Welcome to the forum

write out a balance equation for the oxidation of I- by OCL- to form I₂ and Cl- and OH-

OCL- + 4H+ + 2e- ==> Cl ₂ + 2H₂O

for the half equation and then get Cl and H₂O into 2 more equations?

The original skeleton equation says Cl^- is formed not Cl₂ so your half reaction is not correct (and also not balanced). Cl^- is the product in the half reaction (no need for 2 more equations)

What is the other half reaction ?

[Lonestar]

yeah i looked it up today and yeah, my half equation for OCl was wrong, i think i got it now

OCl^- + 2H+ + 2e^- ==> Cl^- + H2O
I- ==> I₂

balancing these 2 dont give me the OH- however....

[Borek]

Instead of H⁺/H₂O use H₂O/OH^- - net effect is the same. It is just a trick, but that's the way you do it

[Lonestar]

you mean replace the H+ on the LHS with H2O and so on?

but the equation starts of as

OCl^- ==> Cl ^- so therefore, dont you need to add a water to the RHS to balance the oxygen on the LHS?

[LQ43]

From OCl^-  -->  Cl^- 

With Borek's suggestion you can add OH^- to the RHS to balance O on the LHS, then add H₂O on the LHS to balance the O and H.

Then balance charges

OCl^- + 2H+ + 2e^- ==> Cl^- + H2O

OR keeping with the H⁺

After this step, add 2OH^- to both sides (and remember that H⁺  +  OH^- = H₂O) , cancel water to simplify and you get the same balanced half reaction.

Balance I^- --> I₂

then add the two equations

[Borek]

These are equivalent (once balanced):

OCl^- + H₂O -> Cl^- + OH^-

OCl^- + H⁺ -> Cl^- + H₂O

Use H⁺, OH^- and H₂O to balance oxygen/hydrogen whichever way suits you. All three are always present in water solution. Usual approach is to use H⁺ in acidic solutions and OH^- in basic ones.

[Lonestar]

oh i see... nice nice, thanks for the help