$7\mathrm{.}3.$ Choose a suitable material of construction for the following duties:

$98$ per cent $\frac{w}{w}$ sulphuric acid at $70C.$

$5$ per cent $\frac{w}{w}$ sulphuric acid at $30C.$

$30$ per cent $\frac{w}{w}$ hydrochloric acid at $50C.$

$5$ per cent aqueous sodium hydroxide solution at $30C.$

Concentrated aqueous sodium hydroxide solution at $50C.$

$5$ per cent $\frac{w}{w}$ nitric acid at $30C.$

Boiling concentrated nitric acid.

$10$ per cent $\frac{w}{w}$ sodium chloride solution.

A $5$ per cent $\frac{w}{w}$ solution of cuprous chloride in hydrochloric acid.

$10$ per cent $\frac{w}{w}$ hydrofluoric acid.

In each case, select the material for a $50mm$ pipe operating at approximately $2$ bar pressure.