Question

1) Balance the reaction between H2SO3 and ClO3- to form SO42- and Cl2 in acidic solution. When you have balanced the equation using the smallest integers possible, enter the coefficients of the species shown.

_H2SO3 + _ClO3- --->_SO42- + _Cl2

Water appears in the balanced equation as a (reactant, product, neither) with a coefficient of . (Enter 0 for neither.) How many electrons are transferred in this reaction?

2)Balance the reaction between Cl- and Cr3+ to form ClO3- and Cr2+ in acidic solution. When you have balanced the equation using the smallest integers possible, enter the coefficients of the species shown.

_Cl- +_Cr3+ --->_ClO3- +_Cr2+

Water appears in the balanced equation as a (reactant, product, neither) with a coefficient of . (Enter 0 for neither.) How many electrons are transferred in this reaction?

I need help please! I'm on my last attempt.

Answer 1

1)

H2SO3 + ClO3- --------------------- SO4-2 + Cl2

    +4        +5                                   +6           0

The oxidation state of S is increases from +4 to +6. SO it undergoes oxidation

The oxidation state of Cl is decreases from +5 to 0. So it undergoes reduction

Oxidation half reaction

H2SO3 ------------------- SO4-2

H2SO3 + H2O ------------------ SO4-2   [ Oxygen atoms are balanced by adding H2O molecues on deficient side]

H2SO3 + H2O ----------------- SO4-2   + 4 H+   [ Hydrogen atoms balanced by adding H+ ions on deficient side

H2SO3 + H2O ----------------- SO4-2   + 4 H+ + 2e- ------(1) charge is balanced by adding electrons on deficient side.

reduction half reaction

ClO3-   ---------------- Cl2

ClO3- -------------- Cl2 + 3 H2O

ClO3- + 6 H+ -------------- Cl2 + 3 H2O

ClO3- + 6 H+ + 5e- -------------- Cl2 + 3 H2O ---------------- (2)

(1) ------------   [H2SO3 + H2O ----------------- SO4-2   + 4 H+ + 2e- ]x5

(2) -----------   [ClO3- + 6 H+ + 5e- -------------- Cl2 + 3 H2O]x2

(1) ------ 5 H2SO3 + 5 H2O ---------------- 5 SO4-2 + 20 H+ + 10e-

(2) ----   2 ClO3- + 12 H+ + 10e- ------------ 2 Cl2 + 6 H2O

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         5 H2SO3 + 2 ClO3- ----------------- 5 SO4-2 + 2 Cl2 + 8 H+ + H2O

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Only one water molecule is present on product side, [ water molecules is present on product side with coefficient of 1]

totally 10 electrons are transferred during the process.[ number of electrons transferred = 10]

2)

Cl- + Cr+3 ------------------ ClO3-       + Cr+2

-1       +3                           +5                 +2

The oxidation state of Cl is increases from -1 to +5. so it undergoes oxidation

The oxidation state of Cr is decreases fromm +3 to +2. so it undergoes reduction

oxdiation half reaction

Cl- ---------------- ClO3-

Cl- + 3H2O ----------- ClO-3

Cl- + 3 H2O ------------- ClO3- + 6 H+

Cl- + 3 H2O ------------- ClO3- + 6 H+ + 6e-   --------------- (1)

reduction half reaction

Cr+3 -------------- Cr+2

Cr+3 + 1e- ----------- Cr+2 ---------------- (2)

(1) ------------ [Cl- + 3 H2O ------------- ClO3- + 6 H+ + 6e- ]x1

(2) ----------- [Cr+3 + 1e- ----------- Cr+2 ]x6

   Cl- + 3 H2O ------------- ClO3- + 6 H+ + 6e-

   6 Cr+3 + 6e- -------------- 6 Cr+2

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Cl- + 6 Cr+3 + 3 H2O --------------- ClO3- + 6 Cr+2 + 6 H+

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water molecules present on reactant side with coefficient of 3.

The number of electrons are transferred is 6.