Question

Given, 1.5 moles of oxygen atoms are present in:
(A) 0.5 moles of $BaC{{O}_{3}}$
(B) 3 moles of $BaC{{O}_{3}}$
(C) 2 moles of $BaC{{O}_{3}}$
(D) 2.5 moles of $BaC{{O}_{3}}$

Answer 1

Hint: The question is completely based on the knowledge of mole concept and stoichiometric coefficients. Certain specific formulas of the compound can give us the answer about the composition of atoms making the same compound.

Complete answer:
Let us solve the given problem-
We have given one compound in the options so we need to search and solve with respect to $BaC{{O}_{3}}$ only.
According to the formulation i.e. $BaC{{O}_{3}}$ we can see that the one mole of compound has one mole of Barium atoms, one mole of Carbon atoms and three moles of Oxygen atoms.
We need to find the moles of compound which will have 1.5 mole of Oxygen atoms; let that be x,
1 mole of $BaC{{O}_{3}}$ $\equiv $ 3 moles of Oxygen atoms
x moles of $BaC{{O}_{3}}$ $\equiv $ 1.5 moles of Oxygen atoms
Thus,
$x=\dfrac{1.5\times 1}{3}=0.5moles$

Therefore, option (A) 0.5 moles of $BaC{{O}_{3}}$ is correct.

Note:
Do note that this problem is very simple, do not complicate it creating confusion and ending up giving wrong answers. Options (B), (C) and (D) is talking about the number of moles greater than 1 which is quite obviously irrelevant.