Name the elements represented by the following symbols:
$(a)$ $Au$
$(b)$ $Ag$
$(c)$ $Hg$
$(d)$ $Sn$

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 $1\, g\, cm^{-3}$.

$(i)$ $(a)$ What do you understand by $1 \text{ amu}$ or $1 \text{ u}$?
$(b)$ How is it linked with relative atomic mass?
$(ii)$ How do we know the presence of atoms if they do not exist independently for most of the elements?

$A$ change in the physical state of matter can be brought about:

Which of the following would weigh the highest?

Find the ratio by mass of the combining elements in the following compounds. (You may use Appendix $-III$)
$(a)$ $CaCO_{3}$ $(b)$ $MgCl_{2}$
$(c)$ $H_{2}SO_{4}$ $(d)$ $C_{2}H_{5}OH$
$(e)$ $NH_{3}$ $(f)$ $Ca(OH)_{2}$