$81.4 \ g$ sample of ethyl alcohol contains $0.002 \ g$ of water. The amount of pure ethyl alcohol in $g$ to the proper number of significant figures is:

Fill in the blanks given below:
$(i)$ The symbol for the quantity of luminous intensity is .......... and the name of its $SI$ unit is ......... .
$(ii)$ The prefixes used for $10^{-18}$ and $10^{18}$ are ............ and ........... respectively.
$(iii)$ The $SI$ unit of density is ......... .
$(iv)$ In the ........ unit of temperature,its negative value is not possible.

What would be the $SI$ unit for the quantity $\frac{p V^{2} T^{2}}{n}$?

The numbers $17.0145$ and $21.0235$ were rounded to three figures after the decimal point. The resulting numbers, respectively, are

How many significant figures are present in the following?
$(i)$ $0.0025$ $(ii)$ $208$ $(iii)$ $5005$ $(iv)$ $126,000$ $(v)$ $500.0$ $(vi)$ $2.0034$

The significant figures in $3400$ are