Question

A gas is found to contain $2.34g$ of nitrogen and $5.34g$ of oxygen. Simplest formula of the compound is:
A.${N_2}O$
B.$NO$
C.${N_2}{O_3}$
D.$N{O_2}$

Answer 1

If we know the weight ratio of the two or more gases in a compound then we can calculate the molar ratio and then finally we can determine the molecular formula of the compound. Molecular formula will be according to the ratio of the molecular weights of the gases.

Complete step by step answer:
First of all let us read about molecular formulas.
Atoms: It is the smallest unit of an element. The elements are made of the same kind of atoms. In the atoms there are three particles: electrons, protons and neutrons.
Electrons: They are the negatively charged particle having negligible mass. They move in the atoms outside the nucleus in a fixed orbit.
Protons: They are positively charged particles. They have mass. They are present in the nucleus (special room in the atoms were neutrons and protons are present).
Neutrons: They have no charge but they have mass. They are also present in the nucleus along with protons.
Gram molecule: It is defined as the number of grams of the substance i.e. the molecular mass of the substance.
Atomic mass: It is defined as the total number of protons and neutrons present in the nucleus of an atom. It is represented by symbol A.
Atomic number: It is defined as the number of protons in the nucleus of an atom. It is represented by symbol Z.
Molecular weight of the substance: It is defined as the sum of the molecular masses of all elements present in the substance.
Number of moles: It is defined as the ratio of mass of the substance to the molecular mass of the substance.
Molecular formula: The molecular composition in the compound is known as molecular formula. For example: The molecule of water is ${H_2}O$ i.e. two atoms of hydrogen with oxygen.
Now here in the question we are given with the mass of nitrogen and oxygen in the gas. And we know that the molecular mass of nitrogen is $14$ and molecular mass of oxygen is $16$. So the number of moles of nitrogen is $\dfrac{{2.34}}{{14}}$ and moles of oxygen is $\dfrac{{5.34}}{{16}}$ and the ratio of the number of nitrogen and oxygen atom in the gas will be as $\dfrac{{2.34}}{{14}}:\dfrac{{5.34}}{{16}} = 1:2$.
So the molecular formula will be as: $N{O_2}$. So option D is correct.

Note: Formula mass: It is defined as the sum of the atomic weights of all the atoms present in the compound. And if the compound is covalent in nature then the formula mass is known as molecular mass and if we are calculating mass of one mole of substance then it is known as molar mass.