The weight percentage of $C$ and $H$ in a hydrocarbon is in the ratio of $4: 1$. What is its empirical formula?

Which of the following is the formula for calcium chlorite?

An organic compound having molecular mass $60$ is found to contain $C = 20\%$,$H = 6.67\%$,and $N = 46.67\%$,while the rest is oxygen. On heating,it gives $NH_3$ along with a solid residue. The solid residue gives a violet color with alkaline copper sulphate solution. The compound is:

One mole of one of the sodium salts listed below,having carbon content close to $14.3 \%$,produces $1 \ mole$ of carbon dioxide upon heating (atomic mass of $Na = 23, H = 1, C = 12, O = 16$). The salt is:

$A$ compound contains $0.25\%$ of a metal with an atomic weight of $59$. If the compound contains one atom of the metal per molecule,what is the minimum molecular weight of the compound?

$20$ carat gold contains ...... $(\%)$ percent gold.