Could somebody please help this is really hard

The answers to your questions are given below

Explanation:

1. 3 Na2SO4

Molecules of Na2SO4 = 3

Na (sodium) = 3 x 2 = 6

S (sulphur) = 3 x 1 = 3

O (oxygen) = 3 x 4 = 12

2. 4 Pb(NO3)2

Molecules of Pb(NO3)2 = 2

Pb (lead) = 4 x 1 = 4

N (nitrogen) = 4 x 2 x 1 = 8

O (oxygen) = 4 x 3 x 2 = 24

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume