What is the mass in grams of one formula unit of Na2SO3
The correct answer and explanation is :
To calculate the mass in grams of one formula unit of sodium sulfite (Na₂SO₃), we need to determine the molar mass of the compound and then use Avogadro’s number to find the mass of a single formula unit.
Step 1: Determine the Molar Mass of Na₂SO₃
The molar mass is calculated by adding the atomic masses of each element in the formula. The atomic masses of sodium (Na), sulfur (S), and oxygen (O) are as follows:
- Sodium (Na): 22.99 g/mol
- Sulfur (S): 32.07 g/mol
- Oxygen (O): 16.00 g/mol
The formula for sodium sulfite is Na₂SO₃, meaning it contains:
- 2 sodium atoms
- 1 sulfur atom
- 3 oxygen atoms
Now, calculate the molar mass:
[
\text{Molar mass of Na₂SO₃} = (2 \times 22.99) + (1 \times 32.07) + (3 \times 16.00)
]
[
\text{Molar mass of Na₂SO₃} = 45.98 + 32.07 + 48.00 = 126.05 \, \text{g/mol}
]
Step 2: Use Avogadro’s Number to Find the Mass of One Formula Unit
Avogadro’s number is (6.022 \times 10^{23}), which tells us the number of formula units in one mole of a substance.
To find the mass of one formula unit, divide the molar mass by Avogadro’s number:
[
\text{Mass of one formula unit} = \frac{\text{Molar mass}}{\text{Avogadro’s number}} = \frac{126.05 \, \text{g/mol}}{6.022 \times 10^{23}}
]
[
\text{Mass of one formula unit} \approx 2.09 \times 10^{-22} \, \text{grams}
]
Conclusion
The mass of one formula unit of Na₂SO₃ is approximately 2.09 × 10⁻²² grams.
This method uses the basic concepts of molar mass and Avogadro’s number to determine the mass of a single formula unit of a compound. By dividing the molar mass by Avogadro’s number, we convert the macroscopic mass of a mole of the substance to the mass of a single formula unit.