A sample of a compound of nitrogen and oxygen contains 1,52 g of N and 3,47 of O. The molar mass of the compound is between 90 g and 95 g. Determine the molecular formula and molar mass of the compound.

Answer 1

To determine the molecular formula and molar mass of the compound, we need to find the ratio of nitrogen (N) to oxygen (O) atoms in the compound.

1. Determine the number of moles of N and O in the sample:
Moles of N = mass of N / molar mass of N = 1.52 g / 14.01 g/mol = 0.108 moles
Moles of O = mass of O / molar mass of O = 3.47 g / 16.00 g/mol = 0.217 moles

2. Find the simplified ratio of moles of N to O by dividing both moles by the smaller value:
Ratio of N to O = 0.108 moles of N / 0.108 moles of N = 1
= 0.217 moles of O / 0.108 moles of N ≈ 2

3. Determine the empirical formula by using the ratio obtained in step 2:
Empirical formula = N1O2 = NO2

4. Calculate the empirical molar mass of the empirical formula:
Empirical molar mass = molar mass of N + (2 * molar mass of O)
= 14.01 g/mol + (2 * 16.00 g/mol)
= 46.01 g/mol

5. Given that the molar mass of the compound is between 90 g and 95 g, we need to determine how many empirical formula units are present in the compound:
Number of empirical formula units = molar mass of the compound / empirical molar mass
= 95 g / 46.01 g/mol
≈ 2.06

Since the number of empirical formula units is greater than 1, the molecular formula of the compound should be a multiple of the empirical formula.

6. Determine the molecular formula by multiplying the empirical formula by whole numbers to obtain a molar mass within the given range:
Potential molecular formula options:
- Multiply the empirical formula by 2: (NO2)2 = N2O4 (Molar mass ≈ 92.02 g/mol)
- Multiply the empirical formula by 3: (NO2)3 = N3O6 (Molar mass ≈ 138.03 g/mol)

Since the molecular mass of the compound is between 90 g and 95 g, the correct molecular formula is likely N2O4 with a molar mass of approximately 92.02 g/mol.