This experiment examines the chemical behaviour of V(V) in 1 M H2SO4 with the po
ID: 1001087 • Letter: T
Question
This experiment examines the chemical behaviour of V(V) in 1 M H2SO4 with the potential reducing agents Zn, Na2SO3, and NaCl.
Q1. Fill out the Eo= and equations for the following boxes.
Redox Half Cell Equations
VO2+ + 4H+ + 3e => V2+ + 2H2O (1.1V)
Zn2+ + 2e => Zn (-0.76V)
O2 + 4H+ + 4e => 2H2O (1.23V)
V3+ + e => V2+ (-0.26V)
VO2+ + 2H+ + e => VO2+ + H2O (1.00V)
SO42- + 4H+ + 2e => H2SO3 + H2O (0.17V)
Cl2 + 2e => 2Cl- (1.35V)
Reaction 1. Place 5 mL of 0.05M M(V) (as V205) in 1M H2SO4 solution in a test tube and add a small amount of Zn dust. Continue adding small amounts of Zn until no further reaction. Record vour observations Reaction 2.When reaction is complete (no further colour change in the presence of undissolved Zn), remove 2-3 ml of solution (dropper) and add to a separate test tube where it is exposed to air. Record your observations. Reacti on 3. Repeat test 1, using solid Na2S03 in place of Za dust. Ir minutes, heat the solution gently over a Bunsen flame. Record your observations. Reaction 4. Repeat test 3, using 0.2 M NaCl solution.Explanation / Answer
Given.
VO2+ + 4H+ + 3e => V2+ + 2H2O (1.1V)
Zn2+ + 2e => Zn (-0.76V)
O2 + 4H+ + 4e => 2H2O (1.23V)
V3+ + e => V2+ (-0.26V)
VO2+ + 2H+ + e => VO2+ + H2O (1.00V)
SO42- + 4H+ + 2e => H2SO3 + H2O (0.17V)
Cl2 + 2e => 2Cl- (1.35V)
10.
1’st half-reactions.
2H+ + VO2+ - --> VO2+ +H2O
2nd half-reaction:
Zn --> Zn2+ + 2e
By adding two half-reactions.
2 VO2+ + Zn + 4H+ --> 2 VO2+ + Zn2++2 H2O
E0cell = Ecellox + Ecellred
Ecellox = 0.76 V , Ecellred = 0.26 V
E 0cell = 0.76 V + 0.26 V = 1.02 V
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