« Home

Home » Chemistry » Shriver & Atkins: Inorganic Chemistry 4e » Student resources » Video Clips » Chapter 14

Shriver & Atkins: Inorganic Chemistry 4e

Chapter 14

Similarities of the ammonium ion to the alkali metal ions
The larger alkali metal ions form precipitates with large, low-charge anions. The standard test for the larger alkali metal cations is the hexanitritocobaltate(III) ion:

3K+(aq) + [Co(NO2)6]3-(aq) → K3[Co(NO2)6] (s)

Ammonium ion behaves much like an alkali metal of between the sizes of potassium and cesium. Thus the ammonium ion, too, gives a precipitate with the same anion reagent:

3NH4+(aq) + [Co(NO2)6]3-(aq) → (NH4)3[Co(NO2)6] (s)

Click here for Streaming Video - BROADBAND      Click here for Streaming Video - DIALUP

 

Reactions of nitrogen monoxide
Nitrogen monoxide can be produced by the reduction of nitrite ion with the weak reducing agent, iron(II) ion:

NO2-(aq) + 2H+(aq) + e- → NO(g) + H2O(l)

Fe2+(aq) → Fe3+(aq) +e-

Nitrogen monoxide is a reducing agent. Nitrogen monoxide reduces permanganate initially to brown solid manganese(IV) oxide and then to aqueous colorless manganese(II) ion, itself being oxidized to some nitrogen dioxide and some nitrate ion:

NO(g) + H2O(l) → NO2(g) + 2H+(aq) + 2e-

NO(g) + 2H2O(l) → NO3-(aq) + 4H+(aq) + 3e-

MnO4-(aq) + 4H+(aq) + 3e-→ MnO2(s) + 2H2O(l)

MnO2(s) + 4H+(aq) + 2e-→ Mn2+(aq) + 2H2O(l)

Nitrogen monoxide reacts with bromine to form nitrosyl bromide:

2NO (g) + Br2(aq) → 2NOBr (aq)

Nitrogen monoxide oxidises iodide to iodine:

NO(g) + 2H2O(l) → NO3-(aq) + 4H+(aq) + 3e-

2I-(aq) → I2(aq) + 2e-

With iron(II) ion, the pentaaquanitrosyliron ion is formed:

[Fe(OH2)2]2+(aq) + NO(g) → [Fe(NO)(OH2)5]2+ (aq) + H2O(l)

Click here for Streaming Video - BROADBAND     Clickhere for Streaming Video - DIALUP

 

Reaction of nitrogen dioxide
First, nitrogen monoxide is produced by the reduction of nitrite ion with the weak reducing agent, iron(II) ion:

NO2-(aq) + 2H+(aq) + e-→ NO(g) + H2O(l)

Fe2+(aq) → Fe3+(aq) + e-

Air is then drawn into the syringe to cause oxidation to red-brown nitrogen dioxide:

2NO(g) + O2(g) → 2NO2(g)

Nitrogen dioxide is a mixed acid oxide, thus reaction with water gives asolution that is highly acidic.

2NO2(g) + H2O(l) two-way arrow HNO3(aq) + HNO2(aq)

Click here for Streaming Video - BROADBAND       Click here for Streaming Video - DIALUP

Copper penny with nitric acid
When concentrated nitric acid is dropped onto a copper penny, the nitric acid is reduced to red-brown nitrogen dioxide gas while the copper metal is oxidized to copper(II) ion. The nitrato-copper(II) complex is green while dilution with water gives the hexaaquacopper(II) ion.

Cu(s) → Cu2+(aq) + 2e-

HNO3(aq) + H+(aq) + e-→  NO2(g) + H2O(l)

Click here for Streaming Video - BROADBAND      Click here for Streaming Video - DIALUP

 

The pH of acid phosphate ions
The assumption by most students is that any ‘acid’ anion will be acidic. The dihydrogen phosphate ion is indeed acidic:

H2PO4-(aq) + H2O(l) two-way arrow H3O+ (aq) + HPO42-(aq)

But the hydrogen phosphate ion is basic:

HPO42-(aq) + H2O(l) two-way arrow OH- (aq) + H2PO4-(aq)

Click here for Streaming Video - BROADBAND      Click here for Streaming Video - DIALUP

 

Formation of carbon from a carbohydrate
Concentrated sulfuric acid can act as a dehydrating agent, as it does in this case, dehydrating sugar to black elemental carbon and water, the latter being produced as steam due to the exothermic nature of the reaction.

C6H12O6(s) sulfuric acid 6C(s) + 6H2O(g)

Click here for Streaming Video - BROADBAND      Click here for Streaming Video - DIALUP