redox training

Topics: Redox, Oxidizing agent, Bromine Pages: 8 (568 words) Published: January 8, 2015
Exercise 7.3 (training!!!)
1.

Find the oxidation numbers of the underlined elements in the following species. (a)
(e)
(i)
(m)
(q)
(u)
(y)

2.

SO3
PbSO4
CoCl42CrO42SO32Ca(NO3)2
Co(NH3)43+

VO2+
CaH2
KMnO4
SCl2
N2
NaOH

(c)
(g)
(k)
(o)
(s)
(w)

HCO3[Al(OH)4]MnO42NO2FeCl3
KOCl

(d)
(h)
(l)
(p)
(t)
(x)

H2S2O7
H2O2
Cr2O72K2SO4
CH4
Pt(CO)4

Which of the following equations represent redox reactions? Specify the species being reduced in each case if applicable.
(a)
(b)
(c)
(d)

NaI(s) +
2K(s) +
2NH3(g)
Zn(s) +

(e) 2KBr(aq)

3.

(b)
(f)
(j)
(n)
(r)
(v)

H2SO4(l) → NaHSO4(s) + HI(g)
2H2O(l) → 2KOH(aq) + H2(g)
+ 3CuO(s) → 3Cu(s) + N2(g) + 3H2O(l)
2AgNO3(aq) → Zn(NO3)2(aq) + 2Ag(aq)
+ Cl2(aq) →

2KCl(aq) +

Br2(aq)

Balance the following redox equations.
(a)
(b)
(c)
(d)
(e)

Cr2O72-(aq) + I-(aq)
MnO4-(aq) + Cl-(aq)
Fe2+(aq) + H2O2(aq)
ClO3-(aq) + Fe2+(aq)
NO2-(aq) + SO32-(aq)







Cr3+(aq) + I2(aq)
Mn2+(aq) + Cl2(g)
Fe3+(aq) + H2O(l)
Cl2(aq) + Fe3+(aq)
NO(g) + SO42-(aq)

(f) Cr2O72-(aq) + SO2(g) → Cr3+(aq) + SO42-(aq)
(g) Fe3+(aq) + Cu(s) → Fe2+(aq) + Cu2+(aq)
(h) MnO4-(aq) + I-(aq) → Mn2+(aq) + I2(g)
4.

For each of the reactions below,
(i) state and explain what would be observed; and
(ii) write an appropriate equation.
(a) adding excess sodium sulphite solution to iodine solution (b) adding aqueous chlorine to potassium bromide solution
(c) adding excess potassium iodide solution to acidified potassium permanganate solution 1

(d) adding excess iron(II) sulphate solution to acidified potassium dichromate solution (e) adding concentrated nitric acid to magnesium ribbons
(f)
(g)
(h)
(i)
(j)
(k)
(l)
(m)
(n)

5.

adding dilute nitric acid to zinc granules
adding concentrated sulphuric acid to solid sodium bromide
adding concentrated sulphuric acid to magnesium
adding iron(II) nitrate solution to acidified potassium permanganate solution adding sodium sulphite solution to bromine water
adding hydrogen sulphide to acidified potassium dichromate solution adding oxygen to potassium iodide in alkaline medium to give iodine and hydroxide adding carbon to concentrated sulphuric acid
adding copper to silver nitrate solution

Complete the following tables.
common oxidizing agent

respective ionic half-equation & observable colour change if any

Ag+(aq)
Cl2(g)
Br2(aq)
MnO4-(aq)
Cr2O72-(aq)
Fe3+(aq)
dilute NO3-(aq)
concentrated NO3-(aq)
concentrated H2SO4(l)

common reducing agent

respective ionic half-equation & observable colour change if any

K(s)
SO32-(aq)
Fe2+(aq)
Br-(aq)
I-(aq)
Chlorine:
property

reaction

equation & observation

aqueous chlorine oxidizes
oxidizing property

bromide ions to bromine
aqueous chlorine oxidizes
2

iodide ions to iodine
reaction with cold dilute
being oxidized and

sodium hydroxide solution

reduced

reaction with hot

simultaneously

concentrated sodium

(disproportionation)

hydroxide solution to give
NaCl, NaClO3 and water

Concentrated / dilute nitric acid:
property

reaction

equation & observation

concentrated nitric acid
oxidizes metals (e.g. Cu)
oxidizing property

hot concentrated nitric acid
oxidizes non-metals
dilute nitric acid oxidizes
metals

Concentrated sulphuric acid:
property

reaction

equation & observation

can oxidize most metals
(e.g. Cu)
oxidizing property

can oxidize most non-metals
(e.g. C, S)
Reactions with sodium
bromide (2 steps)

Aqueous sulphur dioxide:
property

reaction

equation & observation

aqueous sulphur dioxide
reducing property

reduces dichromate ions to
chromium(III) ions

3

4

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