[majuji]

Please Help me answer this question i really need to undrstand it for a fast approaching exam.

50 mL of a 0.0435 mol dm-3 solution of V2O5 was pipetted into a flask and then reduced with a zinc-mercury amalgam. The solution was later titrated by oxidation with standardized KMnO4 solution (0.0500 mol dm-3). The average titre was 34.97 mL of KMnO4.

Calculate the oxidation state of vanadium after this reduction. Show all steps in your calculation and write a balanced equation for the reaction with permanganate.

thank you very much for your help.

[Arkcon]

Per forum rules you should show your attempts at solving the problem before receiving help.

Try to set up the final calculation:  What would 34.97 ml of 0.0500 M KMnO4 do to the sample of vanadium sulfate?  You can try writing a balanced chemical reaction, although you don't know what the vanadium sulfate was reduced to by the zinc amalgam.

[majuji]

Hey there... i know i am meant to have a go at the problem but to be honest i dont have much of an idea on how to go about solving it. so please if anyone can show me how to do it will be appreciated hugely. you will make my day if you helped. thank you again... anyone

[majuji]

Please Help me answer this question i really need to understand it for a fast approaching exam.

50 mL of a 0.0435 mol dm-3 solution of V2O5 was pipetted into a flask and then reduced with a zinc-mercury amalgam. The solution was later titrated by oxidation with standardized KMnO4 solution (0.0500 mol dm-3). The average titre was 34.97 mL of KMnO4.

Calculate the oxidation state of vanadium after this reduction. Show all steps in your calculation and write a balanced equation for the reaction with permanganate.

Here is my attempt:

meq KnO4- = 0.0500 mmol/mL x 5 meq/,,ol x 34.58 mL = 8.74 meq MnO4-
mmol V = 50.0 mL x 0.0435 x 2 V/V2O5 = 4.35 mmol V
8.74 meq / 4.35 mmol = 2 meq/mmol V thus V was reduced from +5 to +3

4 MnO4- + 10 V+3 + 9 H2O -----> 4 Mn++ + 5 V2O5 + 18 H.

thank you very much for your help.

[Borek]

Logic looks OK to me, haven't checked numbers.