Question

What is the empirical formula of vanadium oxide, if 2.74 g of metal oxide contains 1.53 g of metal?
(Atomic mass: V = 52, O = 16)

Answer 1

Solve the question by hit and trial method. Evaluate each option with the data given in the question and try to find the option closest to the values. Find the total mass of the compound. This will work because the ratio will remain the same in case of the empirical formula as well.

Complete answer:
In chemistry, the empirical formula of a chemical compound indicates the simple positive integer ratio of atoms present in a compound.
It is given to us that in every 2.74 g of the compound, there is 1.53 g of metal i.e. vanadium in this case.
We will now calculate the percentage of metal in the compound. Divide 2.74 by 1.53
This will give us the value, 0.6.
We will now take a compound from the given set of options and check if the ratio remains the same.
The compound under consideration is ${{V}_{2}}{{O}_{3}}$.
Total mass of ${{V}_{2}}{{O}_{3}}$ is 152 g
Total mass of vanadium metal in the compound is 104 g
Ratio = 0.6 .
Therefore, our assumption is right and the empirical formula is ${{V}_{2}}{{O}_{3}}$.

Hence the correct answer is option (A).

Note:
It is important to know that empirical formula gives a simple ratio of atoms present in the compound. You cannot determine a molecular formula with the empirical formula alone. Structure formula cannot be determined as well by this method.