How to Calculate the Number of Moles in 75.0 g of Dinitrogen Trioxide
If you need to calculate moles from grams in chemistry, the process is always rooted in one core idea: every compound has a fixed molar mass, and that molar mass links mass in grams to amount in moles. For dinitrogen trioxide, written as N₂O₃, the question is: how many moles are present in 75.0 grams? This is a classic stoichiometry conversion used in high school chemistry, general chemistry, and exam practice.
The general equation is: n = m / M, where n is moles, m is mass in grams, and M is molar mass in grams per mole. Once you determine the molar mass of N₂O₃, the rest is a direct division.
Step 1: Find the Molar Mass of N₂O₃
Dinitrogen trioxide has:
- 2 nitrogen atoms (N)
- 3 oxygen atoms (O)
Using common atomic masses:
| Element | Atomic Mass (g/mol) | Count in N₂O₃ | Contribution (g/mol) |
|---|---|---|---|
| Nitrogen (N) | 14.007 | 2 | 28.014 |
| Oxygen (O) | 15.999 | 3 | 47.997 |
| Total molar mass | - | - | 76.011 g/mol |
So the molar mass of N₂O₃ is approximately 76.01 g/mol.
Step 2: Use the Mole Formula
Insert the known values into the formula:
Rounded to three significant figures (to match 75.0 g), the answer is: 0.987 mol of N₂O₃.
Final Answer
The number of moles in 75.0 g of dinitrogen trioxide is: 0.987 mol N₂O₃.
Why This Conversion Matters in Chemistry
Mole calculations are foundational because chemical equations operate in mole ratios, not gram ratios. Once mass is converted to moles, you can:
- Predict products and reactant requirements in stoichiometry.
- Calculate limiting reagents and theoretical yield.
- Convert to particles using Avogadro's number.
- Relate gaseous volume to amount under given conditions.
In practical terms, converting 75.0 g of N₂O₃ into 0.987 mol gives you the quantity needed for balanced reaction calculations and concentration work.
Common Mistakes to Avoid
- Using the wrong chemical formula: N₂O₃ is not the same as NO₂ or N₂O₅.
- Adding atomic masses incorrectly: always multiply by each element’s subscript first.
- Inverting the formula: for grams to moles, divide by molar mass.
- Ignoring significant figures: report with precision consistent with given data.
Practice Extension: Reverse Conversion
If you had 0.987 mol of N₂O₃ and wanted grams, you would multiply: mass = moles × molar mass = 0.987 × 76.01 ≈ 75.0 g. This confirms the conversion is consistent.
FAQ: 75.0 g of Dinitrogen Trioxide to Moles
Approximately 76.01 g/mol based on standard atomic masses of nitrogen and oxygen.
0.9867 mol, which rounds to 0.987 mol.
n = m / M, where n is moles, m is grams, and M is molar mass in g/mol.
Because 75.0 g has three significant figures, the final answer should typically match that precision.