Chemistry - volumetic analysis

2010-02-14 9:44 pm

Q1) i. To make up 25 mL of 0.008M KMnO4, how many grams of pure KMnO4 are required?

ii. Calculate how many mL of 0.40 M FeSO4 this sample of solution requires for complete reaction in acidified solution.

Q2) Titraion of 25mL of acidified ron(ll) sulfate solution with potassium permanganate solution of concentration(0.0500 mol/L) gives an average titre value of 24mL. Calculate the concentration of the ferrous sulfate solution.

Q3)
A) Given that H2C2O4 --> CO2, balance the half-equation for this reaction.

B) Hence write a balanced chemical equation for its reaction with permangante ions.

C) Calculate the concentration of permanganate ions. ( use mole ratio obtained in B)
The volume of oxalic acid in each titration is 20mL. The average titre value is 20.4mL. (oxalic acid H2C2O4, 0.0956mol/L)

Thanks a LOT!

回答 (1)

小云

2010-02-14 10:11 pm

✔ 最佳答案

25ml=25cm3
KMnO4的摩爾數:0.008X25/1000
=0.0002mol
KMnO4的摩爾質量:39.1+54.9+16X4
=158gmol-1
KMnO4質量:158X0.0002
=0.0316g

ii)5Fe2+(aq)+MnO4-(aq)+8H+(aq)生成5Fe3+(aq)+Mn2+(aq)+4H2O(l)
從方程Fe和MnO4-的摩爾比　5:1
0.4xV/5=25x0.08
=25cm3=25ml

Q2) H2C2O4(aq)生成2CO2(g)+2H+(aq)+2e-

B)5H2C2O4(aq)+2MnO4-(aq)+6H+(aq)生成10CO2(g)+2Mn2+(aq)+8H2O(l)

C)H2C2O4 : MnO4 5:2
20x0.0956/5=20.4xM/2
M=0.0375M

2010-02-14 14:13:38 補充：
ii)打少左一個小數位
應該是0.4XV/5=25X0.008
V=2.5cm3=2.5ml

參考: my

👍 0 👎 0