Question

How many total atoms are in 0.250 g of p2o5?

Answer 1

There are 2 P atoms and 5 O atoms which results in a total of 7 atoms per molecule. Hope this helps you out; I had the same question yesterday on my 9th grade Physical Science test. 
  

Answer 2

Answer:

3.71 × 10²¹ atoms

Explanation:

The molar mass of P₂O₅ is 283.89 g/mol. The moles of P₂O₅ corresponding to 0.250 g of P₂O₅ are:

0.250 g × (1 mol/283.89 g) = 8.81 × 10⁻⁴ mol

In 1 mole of P₂O₅ there are 6.02 × 10²³ molecules of P₂O₅ (Avogadro's number). In 8.81 × 10⁻⁴ moles of P₂O₅, the molecules of P₂O₅ are:

8.81 × 10⁻⁴ mol × (6.02 × 10²³ molecule/ 1 mol) = 5.30 × 10²⁰ molecule

In 1 molecule of P₂O₅, there are 7 atoms (2 atoms of P and 5 atoms of O). In 5.30 × 10²⁰ molecules of P₂O₅, the number of atoms is:

5.30 × 10²⁰ molecule × (7 atom/1 molecule) = 3.71 × 10²¹ atom