The mass of carbon to the mass of oxygen in carbon dioxide is always _____ in ratio.

The chemical formula of carbon dioxide= CO₂

Mass of 1 carbon atom= 12 u

Mass of 1 Oxygen atom= 16 u

Mass of 2 oxygen atoms= $2\times 16\mathrm{u}= 32 \mathrm{u}$

The mass ratio of carbon to oxygen in carbon dioxide is = $\frac{12}{32}=\frac{3}{8}$

Hence, Whatever the source of carbon dioxide, the mass of carbon to the mass of oxygen in ammonia is always 3:8.