Silver has a density of 10.5gcm^-3 . The no. of silver atoms on a surface area of 10^-12m² can be expressed in scientific notation aas y x 10^x.The value of x is ..?

The ans is x= 7 ..plzz explain.!

Dear Ranjita,

d = mass/V
⇒ 10.5 g/cc means in 1 cc ⇒ 10.5 g of Ag is present.
Number of atoms of Ag in 1 cc ⇒ A
10.5 N
108 ×
In 1 cm , number of atoms of Ag 3
A
10.5 N
108
=
In 1 cm2, number of atoms of Ag
2 /3
A
10.5 N
108
In 10−12m2 or 10−8 cm2, number of atoms of Ag
2 / 3 24 2 / 3
8 8
A
10.5 N 10 1.05 6.022 10 10
108 108
= 1.5 × 107
Hence x = 7

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