The atomic numbers of three elements $A, B$ and $C$ are $9, 10$ and $13$ respectively. Which of them will form a cation?

Which of the following contains the maximum number of molecules?

In photosynthesis,$6$ molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose having a molecular formula $C_6H_{12}O_6$. How many grams of water would be required to produce $18\, g$ of glucose? Compute the volume of water (in $cm^3$) so consumed assuming the density of water to be $1\, g\, cm^{-3}$.

Which will be chemically more reactive: element $A$ with atomic number $17$ or element $B$ with atomic number $16$? Give a reason as well.

State the law of constant proportions.

Calculate the number of moles in $90 \text{ g}$ of water. (in $\text{ moles}$)