Question

How many atoms would be present in a black dot marked on the paper with graphite pencil as a full stop at the

end of a sentence. [Given mass of a dot = 10
power-18 g]. ​

Answer 1

Explanation:

How many atoms would be present in a black dot marked on the paper with graphite pencil as a full stop at the end of a sentence. Thus, 12 g of carbon atoms has 6.022 x 1023 atoms. = 5.02 × 104 carbon atoms.

Answer 2

$5.018\times 10^{4}$  atoms.

Explanation:

Given: Mass of a pencil dot $m = 10^{-18}$

To find: Number of atoms in pencil dot

Formula to be used:

• 1 mole of a substance $= N_a$ particles
• 1 mole of a substance =  Molar mass
• Molar mass  $= N_a$ particles

Solution:

• The molar mass of carbon$= 12 g/mol$

• $N_a = 6.022\times 10^{23}$

Hence,

12 g of C $= 6.022\times 10^{23}$atoms

Now, using the unitary method

$1 g =\frac{6.022\times 10^{23}}{12}$atoms

So, the carbon dot will have

$10^{-18} g =\frac{6.022\times 10^{23}}{12}\times 10^{-18}$atoms

$10^{-18} g = 0.5018\times 10^{23}\times 10^{-18}$atoms

$10^{-18} g = 0.5018\times 10^{5}$atoms

$10^{-18} g = 5.018\times 10^{4}$atoms

Thus, the carbon dot contains $5.018\times 10^{4}$ atoms.