CHEMICAL PROPERTIES OF TRIOXONITRATE (V) ACID

SECOND TERM E-LEARNING NOTES

SUBJECT: CHEMISTRY

CLASS: SS 2

SCHEME OF WORK

WEEK 8 TOPIC

1. NITROGEN: COMPOUNDS OF NITROGEN: TRIOXONITRATE(V) ACID –

LABORATORY PREPARATION AND PHYSICAL PROPERTIES

2. CHEMICAL PROPERTIES OF TRIOXONITRATE (V) ACID

3. USES OF TRIOXONITRATE (V) ACID

4. TRIOXONITRATE(V) SALTS- ACTION OF HEAT, TEST FOR TRIOXONITRATE(V)

IONS.

PERIOD 1: NITROGEN: COMPOUNDS OF NITROGEN: TRIOXONITRATE(V) ACID –

LABORATORY PREPARATION AND PHYSICAL PROPERTIES

LABORATORY PREPARATION OF TRIOXONITRATE (V) ACID

Trioxonitrate (v) acid is prepared by heating solid sodium trioxonitrate (v) with concentrated tetraoxosulphate (vi) acid.

NaNO₃ + H₂SO₄ HNO₃ + NaHSO₄

The apparatus used is completely made of glass because rubber and cork are attack by trioxonitrate (v) acid. The trioxonitrate (v) acid produced in this case is yellow in colour due to the slight decomposition of the acid by heat to produce reddish-brown gas (nitrogen (iv)) which then dissolve in the acid to impart the yellow colour.[mediator_tech]

4HNO₃ H₂O + 4NO₂ + O₂

PHYSICAL PROPERTIES OF TRIOXONITRATE (V) ACID

1. It is corrosive and readily destroys organic materials.
2. It turns blue litmus paper red.
3. It is a colourless liquid which fumes in air on exposure.

EVALUATION:

1. Explain why trioxonitrate (v) acid produced in the laboratory is yellow in colour.

1. Why is all-glass apparatus used in the preparation of trioxonitrate (v0 acid.
2. State three physical properties of trioxonitrate (v0 acid.

PERIOD 2: CHEMICAL PROPERTIES OF TRIOXONITRATE (V) ACID

1. Reaction as an acid:

(a) It reacts with base to form salt and water

HNO₃ + NaOH NaNO₃ + H₂O

(b) It reacts with trioxonitrate (v) to liberate carbon (iv) oxide

HNO₃ + CaCO₃ Ca(NO₃)₂ + H₂O + CO₂

1. As an oxidizing agent:

(a) with metals: Trioxonitraye (v0 acid is a strong oxidizing agent and the oxidizing power of trioxonitrate (v) acid depends on its concentration. In concentrated form, it oxidizes certain metal to trioxonitrate (v) while the acid is reduced to nitrogen (iv) oxide and in moderately concentrated form it reduced to nitrogen (ii) oxide.

Cu + 4HNO₃ Cu(NO₃)₂ + 2H₂O + 2NO₂

3Cu + 8HNO₃ 3Cu(NO₃)₂ + 4H₂O + 2NO

Lead, mercury and silver react in similar way to copper with the metal

Magnesium, zinc nad iron react with dilute trioxonitrate (v) acid to give ammonium trioxonitrate (v0 or nitrogen (i) e.g

4Zn + 10HNO₃ 4Zn(NO₃)₂ + 3H₂O + NH₄NO₃

Aluminium and iron do not react with concentrated HNO₃ due to initial formation of an oxide coating on the metal, which prevent further reaction.

(b) With non-metals: Hot concentrated tetraoxosulphate (vi) acid oxidizes non-metals to their oxides, which may dissolve in water to for the corresponding acids.

C + 4HNO₃ CO₂ + 2H₂O + 4NO₂

S + 6HNO₃ H₂SO₄ + 2H₂O + 6NO₂

P + 5HNO3 H₃PO₄ + H₂O + 5NO₂

I₂ + 10HNO₃ 2HIO₃ + 4H₂O + 10NO₂

EVALUATION:

1. Explain why metals can displace hydrogen from trioxonitrate (v0 acid.
2. State three chemical properties of trioxonitrate (v0 acid

PERIOD 3: USES OF TRIOXONITRATE (V) ACID

1. It is an important raw material for the manufacture of many useful trioxonitrate (v0 salts and organic nitro-compounds such as those used for making dyes. Explosives, fertilizers and drugs.
2. It is used for making of nylon and terylene.
3. It is useful oxidizing agent for many purposes in the laboratory.

EVALUATION:

State four uses of trioxonitrate (v0 acid.

PERIOD 4: TRIOXONITRATE(V) SALTS- ACTION OF HEAT, TEST FOR TRIOXONITRATE(V)

IONS.

All trioxonitrate (v) salts are decomposed by heat.

(a) Trioxonitrate (v0 of sodium and potassium are decomposed to the dioxonitrate (iii) compound and oxygen.

NaNO₃ NaNO₂ + O₂

(b) Trioxonitrate (v) of Zn, Cu, Fe, Mg, Ca, Pb and Al are decomposed to the oxide of the metal, nitrogen (iv) oxide and oxygen.

2Pb(NO₃)₂ 2PbO + 4NO₂ + O₂

(c) Trioxonitrate (v) of Hg and Ag are decomposed to the metal, oxygen and nitrogen (iv0 oxide because the metal oxides are unstable to heat

2AgNO₃ 2Ag + 2NO₂ + O₂

TEST FOR TRIOXONITRATE (V0 IONS

BROWN RING TEST

Acidify an unkwon solution with dilute tetraoxosulphate (vi) acid, then add some freshly prepared iron (ii) tetraoxosulphate (vi) and shake. Then keep the test tube in a slanting position and carefully add some concentrated tetraoxosulphate (vi) acid down the side of the test tube. A brown ring will be formed ar the junction of the two liquid layers. This shows that the unknown contains trioxonitrate (v) ions. the brown ring is FeSO₄.NO[mediator_tech]

GENERAL EVALUATION:

OBJECTIVE TEST

1. Nitrogen combines directly with metals except (a) Ca (b) Mg (c) Cu (d) Al
2. Oxidation number of nitrogen in Mg₃N₂ is (a) -3 (b) +3 (c) -2 (d) +2
3. Hydride of nitrogen which is capable of turningred litmus blue make nitrogen to have an oxidation state of (a) +2 (b) -2 (c) +3 (d) -3
4. Pyre trioxonitrate (v0 acid is colourless but the product of its laboratory preparation is yellow because of the presence of dissolved (a) sulphur (b) sulphur (iv) oxide (c) nitrogen (iv) oxide (d) nitrogen (ii) oxide
5. Which of the following will not leave a solid residue when decomposed by heat? (a) (NH₄)₂SO₄ (b) NaNO₃ (c) Ca(NO₃)₂ (d) KNO₃

ESSAY

1. Explain what is observed when lead (ii) trioxonitrate (v) is heated.
2. Explain why iron (ii) tetraoxosulphate (vi) is always prepared freshly whenever is to be used for analysis.
3. Explain why trioxonitrate (v) acid is not used to acidify KMnO₄ solution.