Copper (ii) oxide can be reduced to copper metal by heating it in a stream of hydrogen gas. dry copper (ii) oxide was placed in a tube which had previously been weighed empty . the tube was reweighed containing the copper (ii) oxide and then set up as in the diagram. Hydrogen was passed through the tube for 15 seconds before the escaping gas was lit . the tube was heated for a few minutes. the apparatus was then allowed to cool with hydrogen still passing through. the tube was reweighed. (a, i) where is the most suitable place to clamp the tube?​