Question

How many total atoms are in 0.280 g of P2O5

Answer 1

First, divide 0.280 by the molar mass of P2O5; that gives you the number of moles. Then multiply the number of moles by 6.023 * 10^23 (Avogadro's number) to get the number of molecules. THEN you have to multiply that value by 7 (since there are 7 atoms per molecule). *Then* you're done.

Answer 2

Answer:

There are 8.43x10²¹ total atoms in 0.280 g of P₂O₅.

Explanation:

Let's follow some steps to calculate the total atoms.

1st) Calculate the molar mass of P₂O₅

Look for the atomic weight of each atom in the Periodic table:

- Atomic weight of Phosphorus = 31 g/mol

- Atomic weight of Oxygen = 16 g/mol

Then, multiply each atomic weight by its coefficient to calculate the molar mass of P₂O₅:

(Atomic weight of P .2) + (Atomic weight of O .5)= Molar mass of P₂O₅

(31 g/mol.2) + (16 g/mol.5) = 62 g/mol + 80 g/mol = 142 g/mol

2nd) Calculate the moles of P₂O₅ that are contained in 0.280 g

This step is easy using a Rule of three thinking that if 142 g of P₂O₅ represents a mol of P₂O₅ the 0.280 g will be "x" moles:

   142 g -------- 1 mol of P₂O₅

0.280 g -------- x = (0.280 g.1 mol)/142 g =0.002 mol of P₂O₅

This means that 0.002 moles of P₂O₅ weights 0.280g.

3rd) Calculate the moles of P and O

To see clear how many moles of each atoms are in the molecule of P₂O₅ we disassociate it:

                                         P₂O₅   →  2P  +  5O

From the reaction we know that 1 mol of P₂O₅ produces 2 moles of phosphorus and 5 moles of oxygen. Now we can make a relation and thinking that if 1 mol of P₂O₅ produces 2 moles of P the 0.002 moles of P₂O₅ that we have will produce "x" moles of P:

        1 mol of P₂O₅ ----- 2 moles of P

0.002 mol of P₂O₅ ----- x = (0.002 mol.2moles)/1mol = 0.004 moles of P

We use the same reasoning for oxygen:

        1 mol of P₂O₅ ------- 5 moles of O

0.002 mol of P₂O₅ ------- x = (0.002 mol.5moles)/1mol = 0.01 moles of O

Up to here we have 0.004 moles of atoms of phosphorus and 0.01 moles of atoms of oxygen.

4th) Calculate the total atoms

To this step it is important to remember that 1 mol of something representa a quantity of 6.022x10²³ (that is called Avogadro's number) So, 1 mol of atoms represents 6.022x10²³ atoms.

Now, if we know that in 1 mol of phosphorus atoms is equal to 6.022x10²³ atoms of phosphorus the 0.004 moles that we have will be equal to "x" atoms:

        1 mol of P ------ 6.022x10²³ atoms of P

0.004 mol of P ------ x = (0.004 . 6.022x10²³)/ 1 = 2.41x10²¹ atoms of P

Use the same reasoning for oxygen:

     1 mol of O ------ 6.022x10²³ atoms of O

0.01 mol of O ------ x = (0.01 . 6.022x10²³)/ 1 = 6.022x10²¹ atoms of O

Now that we have the number of atoms of phosphorus and oxygen let's sum them to find the total atoms:

2.41x10²¹ atoms of P + 6.022x10²¹ atoms of O = 8.43x10²¹ total atoms

Finally, there are 8.43x10²¹ total atoms (of phosphorus and oxygen) in 0.280 g of P₂O₅.