(i) Answer the following questions:
a) Write the balanced chemical reaction for reaction of Cu with dilute `HNO_(3)`.
b) Draw the shape of `ClF_(3)`
(ii)‘X’ has a boiling point of 4.2K, lowest for any known substance. It is used as a diluent for oxygen in modern diving apparatus. Identify the gas ‘X’. Which property of this gas makes it usable as diluent? Why is the boiling point of the gas ‘X’ so low?

Explanation

(a) `3Cu+8HNO_(3)` (dilute) `rarr3Cu(NO_(3))_(2)+2NO+4H_(2)O`

(ii)‘X’ is Helium
It is used as a diluent for oxygen in modern diving apparatus because of its very low solubility in blood.
It monoatomic having no interatomic forces except weak dispersion forces and has second lowest mass therefore bp is lowest.