Revise smart, understand Better

5/58 MCQs for:

ENVIRONMENTAL EDUCATION: Chemistry In Society - Extraction Of Metals

The equation that converts copper (I) oxide to metallic copper by auto-reduction with copper (I) sulphid is:

Cu₂ S_(s) + O_{2 (g)} → 2Cu_(s) + SO_{2 (g)}.

Cu₂ S_(s) + 2Cu₂O_(s) → 6Cu_(s) + SO_{2 (g)}.

Cu₂ S_(s) + FeO_(s) + SiO_{2 (s)} → Cu₂S_(s) + FeSiO_{3 (l)} (Iron II silicate).

2Cu₂ S_(s) + 3O_{2 (g)} → 2Cu₂O_(s) + 2SO_{2 (g)}.

Copper is used in metalwork because:

It is resistant to corrosion and has an attractive appearance.

It is a very good conductor of electricity.

It has low density.

It is light.

Iron is used in the construction of roads, bridges and buildings because of:

It high tensile strength.

It is hard and malleable.

Its magnetic properties.

Its hardness.

Moderately reactive metals are extracted by:

Mining.

Chemical reduction.

Thermal reduction.

Electrolytic reduction.

The electrolyte for the electrolysis of alumina is prepared by dissolving alumina in molten cryolite. This is necessary because:

Molten cryolite also increases the ionization of alumina and hence increases its electrical conductivity.

Pure alumina has a low melting point of about 950℃ which is not readily available. It then dissolved in molten cryolite which increases the melting point to about 2050 ℃.

Pure alumina has a high melting point of about 2050℃ which is not readily available. It then dissolved in molten cryolite which lowers the melting point to about 950 ℃ and molten cryolite also increases the ionization of alumina and hence increases its electrical conductivity.

Pure alumina has a high melting point of about 2050℃ which is not readily available. It then dissolved in molten cryolite which lowers the melting point to about 950 ℃.