Exercise 8.

a)Compare melting point, boiling point, relative density and relative atomic mass of bismuth and cobalt using comparative and superlative degrees. Then compare these both metals with the following elements using the scheme given in Lesson 4.:

1. potassium;

2. beryllium;

3. lithium;

4. magnesium;

5. iron;

6. cadmium.

b)Chemical quiz: Are these sentences true or false:

1. Diamond is very soft.

2. Carbon has one amorphous form.

3. Cobalt steel contains iron, chromium, vanadium, sulpher, hydrogen and cobalt.

4. Graphite is very hard.

5. Cobalt was discovered by Mendeleev.

6. Carbon is a ferromagnetic metal, but cobalt is a diamagnetic.

Bismuth and lead are similar.

8. Beryllium, the first member of the group, has anomalous properties because of the small size of molecule.

c)Grammar and lexical quiz: Find and correct the mistakes:

1. The metal oxideze by hot air.

2. Contains cobalt steel vanadium 12%.

3. They is very hardly.

4. Addition of potassium hydroxide in solution of nitrate cobalt (II) give bluishe-violete precipitate.

5. This element have anomalous properties.

6. What does the first membe of these group?

7. Small amount of metall cobalt is present among meteorites.

8. Lithum reat in water much slowly that other metals.

9. Graphite is very hard substance;

d)Divide the following sentences into two sentences:

1. The compound is readily oxidized in air to form tricobalt tetroxide and is readily reduced by hydrogen to the metal.

2. On heating it readily forms Co₃O₄ which contains both Co (II) and Co (III), and is easily reduced to the metal by hydrogen.

3. The metal is oxidized by hot air and also reacts with carbon, phosphorus, sulphur and dilute mineral acids.

Texts for educational purposes

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Practice	\|	Iron and its compounds

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