Q. A $0.24g$ sample of compound of oxygen and boron was found by analysis to contain $0.096g$ of boron and $0.144g$ of oxygen. Calculate the percentage composition of the compound by weight.

Q. Calculate the number of molecules of sulphur$\left(S_8\right)$ present in $16g$ of solid sulphur.

Q. When $3.0g$ of carbon is burnt in $8.00g$ oxygen, $11.00g$ of carbon dioxide is produced? What mass of carbon dioxide will be formed when $3.00g$ of carbon is burnt in $50.00g$ of oxygen? Which law of chemical combination will govern your answer?

Q. What is the mass of : $\left(a\right)$ $0.2$ mole of oxygen atoms? $\left(b\right)$ $0.5$ mole of water molecules?

Q. Convert into mole.
$\left(a\right)$ $12$ g of oxygen gas
$\left(b\right)$ $20$ g of water
$\left(c\right)$ $22$ g of carbon dioxide.

Q. What is the mass of$-$
$\left(a\right)$ $1$ mole of nitrogen atoms?
$\left(b\right)$ $4$ moles of aluminium atoms(Atomic mass of aluminium $=27)?$
$\left(c\right)$ $10$ moles of sodium sulphite $\left(N{a}_{2}S{O}_3\right)?$

Q. Write the chemical formula of the following.
$\left(a\right)$ Magnesium chloride
$\left(b\right)$ Calcium oxide
$\left(c\right)$ Copper nitrate
$\left(d\right)$ Aluminium chloride
$\left(e\right)$ Calcium carbonate

Q. What are polyatomic ions? Give examples.

Q. Calculate the number of aluminium ions present in $0.051g$ of aluminium oxide.

Q. Give the names of the elements present in the following compounds.
$\left(a\right)$ Quick lime
$\left(b\right)$ Hydrogen bromide
$\left(c\right)$ Baking bromide
$\left(d\right)$ Potassium sulphate.

Q. Calculate the molar mass of the following substances.
$\left(a\right)$ Ethyne, $C_2{H}_2$
$\left(b\right)$ Sulphur molecule, $S_8$
$\left(c\right)$ Phosphorus molecule, $P_4$(Atomic mass of phosporus $=31$)
$\left(d\right)$ Hydrochloric acid, $HCl$
$\left(e\right)$ Nitric acid, $HN{O}_3$