How many oxygen atoms are there in 19.6 g of phosphoric acid?

To solve this problem, we write down given: m (H3PO4) = 19.6 g
Find: the number of oxygen atoms contained in phosphoric acid.
Solution:
Let’s write down the formula for calculating the number of atoms:
v = N / NA
N = v * NA
NA – Avogadro’s constant, which is 6.02 * 10 ^ 23 mol ^ (- 1)
Let’s calculate the amount of substance according to the formula:
v = m / M
Let’s calculate the molar mass:
M (H3PO4) = 1 * 3 + 31 + 16 * 4 = 98 g / mol
Substitute the data and calculate the amount of substance.
v = 19.6 / 98 = 0.2 mol
Let’s calculate the number of atoms.
N = 0.2 mol * 6.02 * 10 ^ 23 mol ^ (- 1) = 1.204 * 10 ^ 23
Answer: N = 1.204 * 10 ^ 23