Question

An Oxide of a Metal (M) contains 40% by mass of Oxygen. Metal (M) has atomic mass of 24.The empirical formula of the oxide Is :

• A. MO
• B. M₂O
• C. M₂O₃
• D. M₃O₄

Answer 1

The correct option is A

MO

Explanation:

Given: Percentage composition of Oxygen (O) = 40 %

Percentage composition is Metal (M)= 100- 40 %= 60 %

Step-1: Calculate the empirical formula

• Empirical formula: Empirical formula is the simplest formula of the compound which gives the simplest whole-number ratio of the atoms of the various elements present in one molecule of the compound. Example: Molecular formula of glucose is C₆H₁₂O₆ but the simplest whole-number ratio of atoms in glucose is CH₂O. Therefore, CH₂O is the empirical formula.

Element	% Of Element	Atomic mass (u)	Atomic ratio $\left(\frac{\%ofelement}{Atomicmass}\right)$	Simplest ratio
Metal (M)	60	24 (given)	$\frac{60}{24}=2.5$	$\frac{2.5}{2.5}=1$
Oxygen (O)	40	16	$\frac{40}{16}=2.5$	$\frac{2.5}{2.5}=1$

As the simplest ratio of Metal is 1 and Oxygen is 1, therefore the empirical formula comes out to be MO.

Hence, option (A) is correct.