Answer to Question #156529 in Chemistry for dede

Question

1.     How many molecules are in are in 3.5 mol of Ca₃(PO₄)₂? How many oxygen atoms are there?    

 

Answer 1

Solution:

(1):

One mole of any substance contains 6.022×10²³ atoms/molecules.

Hence,

Number of Ca₃(PO₄)₂ molecules = 3.5 mol × (6.022×10²³ molecules / 1 mol) = 2.1077×10²⁴ molecules

Number of Ca₃(PO₄)₂ molecules = 2.11×10²⁴ molecules

(2):

The schematic equation:

Ca₃(PO₄)₂ → 3Ca + 2P + 8O

According to the equation above: n(Ca₃(PO₄)₂) = n(O)/8

n(O) = n(Ca₃(PO₄)₂) × 8 = 3.5 mol × 8 = 28 mol

n(O) = 28 mol

One mole of any substance contains 6.022×10²³ atoms/molecules.

Hence,

Number of O atoms = 28 mol × (6.022×10²³ atoms / 1 mol) = 1.6862×10²⁵ atoms

Number of O atoms = 1.69×10²⁵ atoms

Answer:

(1): 2.11×10²⁴ Ca₃(PO₄)₂ molecules are in 3.5 mol of Ca₃(PO₄)₂.

(2): 1.69×10²⁵ oxygen (O) atoms (or 28 mol) are in 3.5 mol of Ca₃(PO₄)₂.