Question

If 4.04 g of nitrogen combine with 11.46 g of oxygen to produce a compound with a molar mass of 108.0 g. What is the molecular formula of this compound?

Answer 1

To find the molecular formula, the moles of nitrogen and oxygen are calculated, then the simplest mole ratio is found. The ratio, combined with the given molar mass, suggests that the molecular formula of the compound is
`N_2 O_5`.

Step-by-step explanation:

The student is asking how to determine the molecular formula of a compound formed from nitrogen and oxygen, given the masses of the elements that combine and the molar mass of the compound.

First, we calculate the moles of nitrogen and oxygen that combined using their molar masses (14 g/mol for nitrogen, 16 g/mol for oxygen) and the given mass. For nitrogen, we have 4.04 g divided by 14 g/mol equals approximately 0.29 moles; for oxygen, 11.46 g divided by 16 g/mol equals approximately 0.72 moles.

Next, we determine the simplest whole number ratio of the moles of nitrogen to the moles of oxygen. Dividing both by the smallest amount, 0.29 moles (the moles of nitrogen), yields roughly a 1:2.5 ratio.

This ratio does not smoothly correspond to whole numbers, so we must consider the possible integers that multiply to give whole numbers and fit the molar mass of 108.0 g.

This suggests the compound may be N2O5, because (2 moles of nitrogen * 14 g/mol) + (5 moles of oxygen * 16 g/mol) = 108 g/mol, which matches the given molar mass of the compound.