Answer:
Solid particles are close together not gas particles
Given :
Number of molecules of hydrogen peroxide, N = 4.5 × 10²².
To Find :
The mass of given molecules of hydrogen peroxide.
Solution :
We know, 1 mole of every compound contains Nₐ = 6.022 × 10²³ molecules.
So, number of moles of hydrogen peroxide is :

Now, mass of hydrogen peroxide is given as :
m = n × M.M
m = 0.0747 × 34 grams
m = 2.54 grams
Hence, this is the required solution.
The number of moles of one substance given the amount in mass can be calculated by the use of the molar mass. This is the mass of a compound per 1 mol of the said substance. For, KCl the molar mass is 74.55 g/ mol
148 g / 74.55 g/mol = 2 mol KCl
Hope this answers the question. have a nice day.