A Nitrogen and Oxygen compound contains 4.2 g of Nitrogen and 12 g of Oxygen. Find the empirical formula. If the molar mass is 756 g per mol, what is the molecular formula?
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A compound of nitrogen and oxygen has 4.2 g of nitrogen and 12 g of oxygen.
As the molar mass of nitrogen is 14 and that of oxygen is 16, the ratio of the number of moles of nitrogen and oxygen in the compound is 1 : 2.5. Multiplying the two by two to yield whole numbers for both gives an empirical formula of 2: 5.
The empirical formula of the compound is N2O5. The molecular mass pf the compound is 756 g/mole. The mass of the empirical formula is 108. This gives a molecular formula of N14O35
The molecular formula of the compound is N14O35.
The compound contains 4.2 g of Nitrogen per 12 g of Oxygen.
now consider atoms mass ratio atom ratio(=mass ratio/at.mass)
N :O 4.2:12.0 4.2/14:12.0/16
=0.3:0.75 = 1:2.5 =2:5
Hence empirical formula of the compound is N2O5
Now suppose the molecular formula be (N2O5)f, where f is a numerical factor.
molar mass = (2x14 + 5x16)f = 108f
by condition 108f = 756
or f= 7 Hence the molecular formula of the compound is (N2O5)7 or, N14O35.
Nitrogen 4.2/14= 0.3 0.3/0.3=1 1*2=2
Oxygen 12/16=0.75 0.75/0.3=2.5 2.5*2=5
Empirical Formula: N2O5
Molar mass= (2*14)+(5*16)=108g/mole
MFM/EFM= Molecular formula
Molecular Formula= (N205)7 OR N14O35
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