Answer: I believe it is B
Explanation:
because it states that a chemical compound always contains exactly the same proportion of elements by mass
M P₂O₅ = 31g×2 + 16g×5 = 142g/mol
1 mole of P₂O₅ contains 5 moles of atoms
5 moles of atoms = 30,01×10²³ a.
142g ----------- 30,01×10²³ a.
0,69g ---------- X
X = (0,69×30,01×10²³)/142
X = 0,14626×10²³ = 1,4626×10²² atoms
:)
