Question

Calculate the number of moles for following 39g of oxygen molecules​

Answer 1

Explanation:

One mole of any substance contains 6.02 X 1023 units of that substance. Equally important is the fact that one mole of a substance has a mass in grams numerically equal to the formula weight of that substance. Thus, one mole of an element has a mass in grams equal to the atomic weight of that element and contains 6.02 X 1023 atoms of the element. For those elements that do not occur as single atoms - that is, the diatomic gases, sulfur, and phosphorus - it is important to be certain that you specify what you are talking about. One mole of atoms of oxygen has a mass of 16 g, as 16 is the atomic weight of oxygen, and contains 6.02 X 1023 atoms of oxygen. One mole of oxygen gas, which has the formula O2, has a mass of 32 g and contains 6.02 X 1023 molecules of oxygen but 12.04 X 1023 (2 X 6.02 X 1023) atoms, because each molecule of oxygen contains two oxygen atoms.

These definitions allow a new definition of atomic weight: The atomic weight of an element is the mass in grams of one mole of naturally occurring atoms of that element.

Using these relationships, we can calculate the number of atoms in a given mass of an element or the mass of a given number of atoms.

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Answer 2

Answer: 1.083 moles

Explanation: Mole of a substance is always calculated by the formula:

$number of moles=\frac{given mass of substance}{molar mass of the substance}$

where molar mass is the mass of the molecule or atom.

Therefore, using above equation:

$\frac{given mass of substance}{molar mass of substance}=\frac{39g}{36 g}$

molar mass of oxygen molecule is 36g/mol

$\\\\number of moles = 1.083 moles$