# Mole Concepts Problems with Solutions

Given below are the Mole Concepts Questions with Detailed Solutions
a. Concepts questions
b. Calculation problems
c. percentage composition
d. Mole fraction & molarity

Known Values

Question 1
How many molecules of water are there in 54 g of $H_2O$ ?

Question 2
Calculate the mass of $6.022 \times 10^{23}$ molecule of $NH_4Cl$ ?

Question 3
Calculate the mass of $12.044 \times 10^{23}$ Oxygen atoms.

Question 4
How many atoms of hydrogen are there in 36 g of $NH_4$?

Question 5
Calculate the number of hydrogen atoms in 1 mole of H2.

Question 6
Calculate the number of Cu atoms in 0.3175 g of Cu.

Question 7
Calculate the number of molecules in 22.4 litres of CH4 gas at NTP.

Question 8
a. Find the volume of 1 g of H2gas in litres at N.T.P
b.Find the volume of 20g H2at NTP.
c.What is the volume occupied by $6.022 \times 10^{23}$ molecules of any gas at NTP?

Question 9
An atom of some element Y weighs $6.644 \times 10^{-23}$ g. Calculate the number of gram-atoms in 40 kg of it.

Question 10
Find the number of moles and number of atoms of H and S in 10 mole of $H_2S$.

Question 11
Calculate the number of atoms of each element in 245 g of $KClO_3$.

Question 12
If 4 g of NaOH dissolves in 36 g of $H_2O$, calculate the Mole fraction of each component in the solution. Also, determine the Molarity of solution (specific gravity of solution is 1 gm/L)

Question 13
Calculate the number of atoms in 12.2 litres of the below gas at NTP
(i) mono-atomic
(ii) diatomic gas

Question 14
If a mole were to contain $1 \times 10^{24}$ particles, what would be the mass of
(i) one mole of oxygen
(ii) a single oxygen molecule?

Question 15
Calculate the standard molar volume of oxygen gas. The density of $O_2$ gas at NTP is 1.429 g/L.

Question 16
if 2 mol of Calcium Carbonate (Formula Weight =100) occupies a volume of 67.0 ml, Find the density ?

Question 17
Calculate how many methane molecules and how many carbon and hydrogen atoms are there in 25 g of Methane?

Question 18
A metal M of atomic mass 54.94 has a density of 7.42g/cc. Calculate the apparent volume occupied by one atom of the metal.

Question 19
Calculate the number of moles of Ca, C and oxygen atoms and its mass in 200 g of $CaCO_3$.

Question 20
Calculate the total number of electrons present in 3.2 g of CH4.

Question 21
How much Calcium is in the amount of Ca(NO3)2 that contains 20.0g of Nitrogen?

Question 22
State the number of atoms in 1 g atom of Aluminium?

Question 23
If the components of the air are N2, 78%; O2, 21%; Ar, 0.9% and CO2, 0.1% by volume, what would be the molecular mass of air?

Question 24
How many molecules are there in 1.624 gm Ferric chloride(FeCl3)?

Question 25
What is the mass of 1 Ammonia Molecule ?

Question 26
The atomic masses of two elements (P and Q) are 20 and 40 respectively. x g of P contains y atoms, how many atoms are present in 2x g of Q?

Question 27
Oxygen is present in a 1-litre flask at a pressure of $7.6 \times 10^{-10}$ mm of Hg at 0°C. Calculate the number of oxygen molecules in the flask.

Question 28
What is the ratio of the volumes occupied by 1 mole of O2and 1 mole of O3in identical conditions?

Question 29
Calculate the mass of .5 moles of CaCO3in g.

Question 30
The cost of the Table Salt(NaCl) and Table sugar($C_{12}H_{22}O_{11}$) is Rs 10 and Rs 40 per kg. Find the cost of the salt and sugar per mole?

Question 31
Calculate the number of oxygen atoms in 0.2 mole of Na2CO3.10H2O.

Question 32
A polystyrene, having the formula $Br_3C_6H_3(C_3H_8)_n$, was prepared by heating styrene with tribromobenzoyl peroxide in the absence of air. If it was found to contain 10.46% bromine by weight, find the value of n.

Question 33
It has been estimated that 93% of all atoms in the entire universe are hydrogen and that the vast majority of those remaining are helium. Based on only these two elements, estimate the mass percentage composition of the universe.

Question 34
The molecular weight of haemoglobin is about 65,000 g/mol. Haemoglobin contains 0.35% Fe by mass. How many iron atoms are there in a haemoglobin molecule?

Question 35
Calculate the Number of atoms of oxygen present in 88g of $CO_2$. What would be the weight of the Carbon monoxide having the same number of oxygen atoms?

Question 36
At room temperature, the density of water is 1.0 g/mL and the density of ethanol is 0.789 g/mL. What volume of ethanol contains the same number of molecules as are present in 175 mL of water?

Question 37
Chlorophyll the green colouring matter of plants responsible for photosynthesis contains 2.68% of Magnesium by weight.Calculate the number of magnesium atoms in 4 g of Chlorophyll

Question 38
Calculate approximately the diameter of an atom of mercury, assuming that each atom is occupying a cube of edge length equal to the diameter of the mercury atom. The density of mercury is 13.6 g/cc.

Question 39
How many years it would take to spend Avogadro number of rupees at the rate of Rs 10 laks per sec?

Question 40
Find the total number of neutrons present in 7 mg of 14C atoms.