Determine the empirical formula of an oxide of iron which has $69.9 \%$ iron and $30.1 \%$ dioxygen by mass.

An organic compound with $C = 40\%$ and $H = 6.7\%$ will have the empirical formula

If two compounds have the same empirical formula but different molecular formulae,they must have:

What is the percentage composition of $C$ in methanoic anhydride?

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:

An organic compound with a molecular weight of $60$ contains $C = 20\%$,$H = 6.67\%$,and $N = 46.67\%$,with the remainder being oxygen. Upon heating,the solid residue gives a violet color with alkaline copper sulfate solution. Identify the compound.