What is the molecular formula of a compound made of 25.9% N and 74.1% O?
a. NO
b. NO₂
c. N₂O
d. N₂O₅
e. N₂O₄
Answer (3)
74.1% + 25.9% = 100%
we assume 100g of sample
100%-----------100g 25.9% N ------------x x 25.9g N
100g - 25.9g = 74.1g O
mass of N = 14g mass of O = 16g
1 mole of N ------------ 14g x moles of N -------------- 25.9g x = 1.85 moles of N
1 moles of O -------------- 16g x moles of O ----------------- 74.1g x = 4.6 moles of O
N : O = 1.85 : 4.6 we share by the smallest value N : O = 1.85 : 4.6 ||:1.85 N : O = 1 : 2.4 ≈ 1 : 2 NO₂ answer: B
D.
If we take a sample of 100g of the given compound, we should find that it contains 74.1g of oxygen and 25.9g of nitrogen. The molar masses of oxygen and nitrogen are approximately 16.0g/mol and 14.0g/mol respectively. To find the appropriate number of moles of oxygen and nitrogen found in one mole of the given compound, we divide the mass of the sample by the molar mass of each substance.
For oxygen: 74.1g/(16.0g/mol) = 4.63125 mol (round up to 5 mol)
For nitrogen: 25.9g/(14.0g/mol) = 1.85 mol (round up to 2 mol)
Therefore one mole of this compound contains 2 moles of nitrogen and 5 moles of oxygen.
The molecular formula of the compound made of 25.9% nitrogen and 74.1% oxygen is N₂O₅, corresponding to option d. This was determined by calculating the number of moles for each element and finding their simplest whole number ratio. Thus, the answer is d. N₂O₅.
;
