# Answer to Question #33742 in Inorganic Chemistry for raj

Question #33742

how many moles and molecules of o2 are there in 64g of O2 .What is the mass of one molecules of O2?

Expert's answer

Moles are in O

n = m/M

= 64g/32g per mol

= 2 moles

Molecule of O

64 g x 1 mol/ 16 g = 64 mol / 16 (grams cancel)

64 / 16 = 4 mol

Then in order to find molecules you need to know avogadro's number, which is basically just the definition and value for the unit mol.

avogadro's number states that

1 mole = 6.02 x 10^23

so, we use a conversion factor again to find how many molecules are in 4 moles.

4 moles X 6.02 X 10^23 / 1 mole = (moles cancel)(multiply 4 and 6.02) = 24.08 x 10^23

You need to move the decimal point so that the number is between 1 and 10. So we move the decimal point once space to the left to create: 2.408 The exponent also needs to change from 10^23 to 10^24 to account for the decimal place we moved. So, in 64 grams of oxygen there are 2.408 x 10^24 oxygen molecules, you should probably just write this answer as 2.4 x 10^24 because this accounts for the significant figures you started out with (you had 2 when we started out with the molar mass of oxygen @ 16) and now, we have two again.

Answer: 2.4 x 10^24

_{2}in 64 grams:n = m/M

= 64g/32g per mol

= 2 moles

Molecule of O

_{2}consisy of 2 anoms, then:64 g x 1 mol/ 16 g = 64 mol / 16 (grams cancel)

64 / 16 = 4 mol

Then in order to find molecules you need to know avogadro's number, which is basically just the definition and value for the unit mol.

avogadro's number states that

1 mole = 6.02 x 10^23

so, we use a conversion factor again to find how many molecules are in 4 moles.

4 moles X 6.02 X 10^23 / 1 mole = (moles cancel)(multiply 4 and 6.02) = 24.08 x 10^23

You need to move the decimal point so that the number is between 1 and 10. So we move the decimal point once space to the left to create: 2.408 The exponent also needs to change from 10^23 to 10^24 to account for the decimal place we moved. So, in 64 grams of oxygen there are 2.408 x 10^24 oxygen molecules, you should probably just write this answer as 2.4 x 10^24 because this accounts for the significant figures you started out with (you had 2 when we started out with the molar mass of oxygen @ 16) and now, we have two again.

Answer: 2.4 x 10^24

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