Question

Convert into mole. 12 g of Oxygen gas.

Answer 1

Hint: For a molecule, molecular weight in grams is equal to the Avogadro number. Hence, by dividing the given mass by the molar mass of the given compound we will get the number of moles in the given sample.

Complete step by step answer:
- Let's start with the idea of Avogadro number and concept of moles. Avogadro’s number can be defined as a proportion which relates the molar mass on an atomic scale to physical mass on a human scale. It is defined as the number of elementary particles such as molecules, atoms, compounds, etc. per mole of a substance.
- Or in other words, Avogadro’s number or Avogadro’s constant is the number of units in one mole of any substance. Its value is given as $6.023\times {{10}^{23}}$.Avogadro number is often denoted as ${{N}_{A}}$
- A major property of Avogadro’s number is that the substance’s molecular weight is equal to the mass of one mole of a substance. Also, the gram molecular mass of a compound refers to the mass of a single mole of the compound. and the gram atomic mass of an element is the mass of one mole of that element.
- Thus, by the above relation we could find the number of moles in a given sample by the following equation
    $Number\text{ }of\text{ }moles~~=\dfrac{Given\text{ }mass~~}{Molar\text{ }mass}~~$

- Oxygen exists in the diatomic form in a gaseous state (${{O}_{2}}$). Therefore, for finding the molar mass of diatomic oxygen we should multiply the atomic mass (16) by two.
Molar mass of ${{O}_{2}}$ = 16×2
                              = 32 $g/mol$
By using the above-mentioned formula, we can write,
Number of moles in 12 g oxygen gas = $\dfrac{12g}{32gmo{{l}^{-1}}}$
                                                             = 0.375 mol
Therefore, 12 g of oxygen gas has 0.375 moles.

Note: We could also find the answer in a simpler way .As we have found that the molar mass of oxygen gas is 32 $g/mol$, it means that 32 g of oxygen gas contains one mole and for finding the number of moles in 12g of oxygen we could just take their ratio and it will give us the answer.