Characteristics of Chemical Reactions

When dilute $\mathrm{HCl}$ is added to zinc pieces taken in a test tube:

Some crystals of copper sulphate were dissolved in water. The colour of the solution obtained would be

Which of the following will be required to identify the gas evolved when dilute hydrochloric acid reacts with zinc metal

Give the characteristics tests for the following gases :
(i) ${\mathrm{CO}}_2$ (ii) ${\mathrm{SO}}_2$ (iii) ${\mathrm{O}}_2$ (iv) ${\mathrm{H}}_2$

A shiny brown coloured element 'X' on heating in air becomes black. Name the element X' and the black coloured compound formed.