$A$ gas is found to contain $2.8 \ g$ of nitrogen and $3.2 \ g$ of oxygen. The simplest formula of the compound is:

An organic compound contains $75\%$ (by weight) carbon and the remaining percentage is hydrogen. The correct option for the empirical formula of this compound is: [Atomic weight of $C = 12$, $H = 1$]

$A$ welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives $3.38 \, g$ of carbon dioxide,$0.690 \, g$ of water,and no other products. $A$ volume of $10.0 \, L$ (measured at $STP$) of this welding gas is found to weigh $11.6 \, g$. Calculate:
$(i)$ empirical formula,
$(ii)$ molar mass of the gas,and
$(iii)$ molecular formula.

On analysis,a certain compound was found to contain iodine and oxygen in the ratio of $254 \ g$ of iodine and $80 \ g$ of oxygen. The atomic mass of iodine is $127$ and that of oxygen is $16$. Which of the following is the formula of the compound?

How many grams of oxygen are present in $32.2 \ g$ of $Na_2SO_4 \cdot 10H_2O$ (in $g$)?

An organic compound on analysis gave the following results: $C = 54.5\%$,$O = 36.4\%$,$H = 9.1\%$. The empirical formula of the compound is: