What is the molar mass of nitrogen gas?
a. 14.0 g/mol
b. 28.0 g/mol
c. 6.02 x 1023 g/mol
d. 1.20 x 1023 g/mol
e. none of the above
The correct answer and explanation is :
The correct answer is b. 28.0 g/mol.
Explanation (around 300 words):
Nitrogen gas, symbolized as ( \text{N}_2 ), is the most abundant gas in Earth’s atmosphere, making up about 78% by volume. It exists naturally as a diatomic molecule, meaning each molecule consists of two nitrogen atoms bonded together.
To calculate the molar mass of nitrogen gas, we first need to know the atomic mass of a single nitrogen atom. According to the periodic table, the atomic mass of nitrogen (N) is approximately 14.0 g/mol. Since nitrogen gas consists of two nitrogen atoms per molecule, we multiply the atomic mass by 2:
[
\text{Molar mass of } \text{N}_2 = 2 \times 14.0\ \text{g/mol} = 28.0\ \text{g/mol}
]
Thus, one mole of nitrogen gas (( \text{N}_2 )) weighs 28.0 grams.
Now, let’s briefly examine the other answer choices:
- a. 14.0 g/mol: This is the molar mass of a single nitrogen atom (N), not nitrogen gas (( \text{N}_2 )).
- c. ( 6.02 \times 10^{23} ) g/mol: ( 6.02 \times 10^{23} ) is Avogadro’s number, representing the number of molecules in one mole, not a molar mass.
- d. ( 1.20 \times 10^{23} ) g/mol: This number doesn’t relate directly to nitrogen’s molar mass.
- e. none of the above: This is incorrect since choice b is correct.
Understanding molar mass is crucial in chemistry because it connects the microscopic world (atoms and molecules) to the macroscopic world (grams and liters that we can measure). It allows chemists to predict how much of a substance is needed for a reaction and to calculate yields.
In summary, the molar mass of nitrogen gas is 28.0 g/mol because it consists of two nitrogen atoms, each weighing 14.0 g/mol.