Chem )46 Pre-Lechne Exane ise #20 Alex ToOk In each case, select the correct hal

Question

Chem )46 Pre-Lechne Exane ise #20 Alex ToOk In each case, select the correct half-reaction. Your choices are a-h. Choices a-d are the same for every question. Choices e-h are unique to salt in question. b. H2(g) + 20H(aq) ? 2 HJX) + 2e. d. O2(g) + 4H+(aq) + 4e ? 2HJX) 1. Consider the electrolysis of an aqueous solution of PbF. The half-reaction occurring at 2 H,O() + 2 e' H2(g) 2 OH(aq) + the cathode is POs) Pb2+(aq) 2e. ? + 2. Consider the electrolysis of an aqueous solution of PbF. The half-reaction occurring at 3. Consider the electrolysis of an aqueous solution of CuBr. The half-reaction occurring e. 2 Br(aq)? Br(g) + 2e. h. Cu2+(aq) +2e-? Cu(s) 4. Consider the electrolysis of an aqueous solution of CuBr,. The half-reaction occurring 5. Consider the electrolysis of an aqueous solution of Na,SO,. The half-reaction occurring e. Na (a)e Na(s) the anode is . See question #1 for choices e-h. at the cathode is Br2(g) + 2e. 2 Br(aq) ? at the anode e is . See question #3 for choices e-h. - at the cathode is s,082-(aq) 2 e. 2 so,2-(aq) + ? 6. Consider the electrolysis of an aqueous solution of Na SO, The half-reaction occurring . See question #5 for choices e-h. at the anode is 6. 2. 3. 4.

Explanation / Answer

1)Aqueous solution of PbF2

PbF2(aq) ------------------- Pb+2(aq) + 2F-(aq)

H2O -------------------- H+ + OH-

at cathode    Pb+2(aq) + 2e- ------------------ Pb(s)

The answer is E.

Among Pb+2 and H+. Pb+2 ions movestowords to the cathode.

2) at anode

2 H2O(l) ---------------- 4H+(aq) + O2(g) + 4e-

The answer is C

F- ion have high discharge potential . so these are not moves towords to the anode .

3)Aqueous solution of CuBr

at cathode         Cu+2(aq) + 2e- --------------- Cu(s)

4) at anode 2 H2O(l) ---------------- 4H+(aq) + O2(g) + 4e-

5)aqueous solution of Na2So4

at cathode Na+(aq) + e----------------- Na(s)

2) electrolysis of moten salts

1) molten CaF2

CaF2 ------------ Ca+2(aq) + 2 F-(aq)

at anode 2 F-(aq) -------------------- F2(g) + 2e-

at anode F2 gas is relesed.

the answer is A

2) at cathode Ca+2(aq) + 2e- ------------------- Ca(s)

at cathode Ca metal is deposited

The answer is D

3) Molten ZnO

ZnO ---------------- Zn+2 (aq) + O-2(aq)

at anode        O-2(aq) ------------------ O2(g) + 2e-

at anode C is formed i,e O2

at cathode Zn+2 + 2e- ------------------- Zn(s)

at cathode Zn is formed .The answer is A.

at anode

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