What is the composition of the white enamel of our teeth?

How many moles of aluminum oxide $(Al_2O_3)$ are produced when $1 \text{ mole}$ of potassium chlorate $(KClO_3)$ undergoes thermal decomposition,and the resulting gaseous product is reacted with excess aluminum?

The number of moles of solute present in the solutions of $I$,$II$ and $III$ is respectively:
$I$. $500 \ mL$ of $0.2 \ M \ NaOH$
$II$. $200 \ mL$ of $0.1 \ N \ H_2SO_4$
$III$. $6 \ g$ of urea in $1 \ kg$ of water

Which of the following is $NOT$ true for $1 \ g$ of Helium?

Iron sulphide is heated in air to form $A$,an oxide of sulphur. $A$ is dissolved in water to give an acid. The basicity of this acid is

In a $20\%$ aqueous solution of $H_2O_2$,the mole fraction of water is $.......$.