Stoichiometry Problems

Question

P4(s) 5O2(g) --> P4O10(g)

1. The number of atoms of phosphorus that will combine with 200 molecules of O2.

2. The number of molecules of P4O10 that form from 2 x 10^8 molecules of O2 and sufficient P4.

3. The number of molecules of P4 left over if 80 P4 molecules are mixed with 120 O2 molecules and the mixture reacts.

4. The number of molecules of O2 needed to form 6.02 x 10^23 molecules of P4O10.

Answer 1

Moles O2 = 200 / 6.02 x 10^23 =3.32 x 10^-22

the ratio between P4 and O2 is 1 : 5

moles P4 = 3.32 x 10^-22 / 5 =6.64 x 10^-23

atoms P = 4 x 6.64 x 10^-23 =2.66 x 10^-22

the ratio between O2 and P4O10 is 5 : 1

Moles P4O10 = 2 x 10^8 / 5 = 4 x 10^7

1 : 5 = x : 120

x = 120 / 5 = 24 = molecules P4 needed

molecules P4 in excess = 120 - 24 = 96

5 : 1 = x : 6.02 x 10^23

x = 5 x 6.02 x 10^23 =3.01 x 10^24

I hope this help you