The answer to each of the following questions is a single digit integer, ranging from 0 to 9. If correct answers to the question number A,B,C and D (say) are 4,0,9 and 2 respectively, then correct darkening of bubbles should be as shown on the side.
(A) Silver (atomic weight = 108 g `mol^(-1)`) has a density of 10.5 g `cm^(-3)`. The number of silver atoms on a surface are of `10^(-12) m^(2)` can be expressed in scientific notation as `yxx10^(x)`. The value x is ...........

Answer

7

Explanation

Volume of 1 mole of Ag aotms `=(108)/(10.5)cm^(3)`
Volume of one Ag atom `=(108)/(10.5xx6.023xx10^(23))`
`=(4)/(3)pir^(3)`
or `r=1.6xx10^(-8)cm=1.6xx10^(-10)m`
where r is the radius of Ag atom
Area occupied by one Ag atom `=pir^(2)`
`=3.14xx(1.6xx10^(-10))^(2)m^(2)`
`:.` no. of Ag atoms of the surface area of `10^(-12)m^(2)`
`=(10^(-12))/(3.14xx(1.6xx10^(-10))^(2))=1.27xx10^(7)`
=x=7