Questions on Materials science introduction

1. Elemental copper does occur in nature, but copper is mainly extracted from its sulfide, carbonate or oxide minerals. Tin does not occur naturally in the elemental state. The main ore of tin is cassiterite, SnO₂. Bronze is an alloy of copper and tin. In ancient civilizations the Stone Age was followed by the Bronze Age, which was then followed by the Iron Age. These are named after the materials that early man used to make tools.

(a) Explain why copper can be found naturally in its elemental state, whereas tin cannot.

(b) One common ore of copper is malachite, which has the formula Cu₂CO₃(OH)₂.
(i) Deduce the oxidation state of copper in this ore.
(ii) Outline with equations how elemental copper can be obtained from this ore.

(c) Even though copper has been known and used by man for about ten thousand years, the Stone Age lasted until about 2500 BC when it was replaced by the Bronze Age. Ötzi, the iceman found in the Alps who lived around 3300 BC , was found to be carrying an axe with a copper head. Suggest why, even though some tools were made from elemental copper, reference is not normally made to a Copper Age.

(d) Suggest why early man discovered and used bronze before iron.

2. Magnesium chloride, MgCl₂, and beryllium chloride, BeCl₂, are both group 2 chlorides.

(a) Identify where they appear on the Triangular Bonding Diagram given in Section 29 of the data booklet.

(b) Explain why the boiling point of beryllium chloride (482 ^oC) is much lower than the boiling point of magnesium chloride (1412 ^oC).

(c) Use the Triangular Bonding Diagram to predict an approximate value for the boiling point of beryllium fluoride, BeF₂.

3. In Option C.7 it states “Intermolecular forces in UF₆ are anomalous and do not follow the normal trends”. Evaluate this statement in terms of the Triangular Bonding Diagram given that the electronegativity of uranium is 1.4.

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