How will you convert a mixture of CO and `CO_2` completely into `CO_2` ?

Explanation

When a mixture of `CO_2` and CO is passed over strongly heated CuO, kept in a combustion tube, `CO_2` remains unchanged while CO gets oxidised to `CO_2`. As a consequence, only `CO_2` comes out of the combustion tube. In this way, the mixture is completely converted into `CO_2`.
`CO+CuO overset(Delta)to CO_2 + Cu`