1.1. An ore of tungsten conatins WO₃. Tungsten can be obtained from WO₃ by reacting it with hydrogen. The reaction is a redox reaction, water is also produced.

Write the balanced symbol equation for the reaction.

1.2. Extended Only

Explain reduction and oxidation in terms of electrons and oxidation numbers.

1.3. Separate: Chemistry and Extended Only

The oxidation number of oxygen is -2 and this remains unchanged during the reaction.

Identify, using oxidation numbers, what has been oxidised and what has been reduced in this reaction.

1.4. Extended Only

50 tonnes of the tungsten ore were processed. The ore was found to contain 3.4% of WO₃ by mass. Calculate the maximum mass, in tonnes, of tungsten that could be obtained from this ore.

Give your answer to three significant figures.

[A_r (W) = 184;    M_r (WO₃) = 232]

maximum mass of tungsten = ................................................. tonnes