Mole Concept questions with answers:

The ratio of weights of hydrogen and helium is 1 : 2. Find the ratio of number of gram atoms.
(a) 2 : 1
(b) 1 : 1
(c) 1 : 4
(d) 4 : 1

Ans. (a)

How many gram atoms of the lightest element weigh same as 1 gram atom of the heaviest element?
(a) 1
(b) 235
(c) 238
(d) 100

Ans. (c)

Which one of the following pairs of gases contains the same number of molecules
(a) 16 g of O₂ and 14 g of N₂
(b) 8 g of O₂ and 22 g of CO₂(c) 28 g of N₂ and 22 g of CO₂
(d) 32 g of O₂ and 32 g of N₂

Ans. (a)

Atoms of which of the following elements exist independently.
(a) Helium
(b) Sodium
(c) Argon
(d) Magnesium

Ans. (a)

, (c)

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Among all the naturally occurring elements, which one can generate the maximum number of gram atoms from a given amount?
(a) Hydrogen
(b) Uranium
(c) Calcium
(d) Mercury

Ans. (a)

Among all the naturally occuring elements, one gram atom of which element contains the maximum amount of it?
(a) Hydrogen
(b) Uranium
(c) Calcium
(d) Mercury

Ans. (b)

Number of gm of oxygen in 32.2 g Na₂SO₄ . 10H₂O is
(a) 20.8
(b) 22.4
(c) 2.24
(d) 2.08

Ans. (b)

Which property of an element is always a whole number?
(a) Atomic weight
(b) Equivalent weight
(c) Atomic number
(d) Atomic volume

Ans. (c)

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250 ml of a sodium carbonate solution contains 2.65 grams of Na₂CO₃. If 10 ml of this solution is diluted to one litre, what is the concentration of the resultant solution (mol. wt. of Na₂CO₃ = 106)
(a) 0.1 M
(b) 0.001 M
(c) 0.01 M
(d) 10^–4M

Ans. (b)

Identify the element whose 2 gram atoms weigh 8g.
(a) Hydrogen
(b) Helium
(c) Oxygen
(d) Sulphur

Ans. (b)

Which of the following exist independently?
(a) Atoms
(b) Molecules
(c) Ions
(d) All

Ans. (b)

, (c)

A molar solution is one that contains one mole of a solute in
(a) 1000 g of the solvent
(b) One litre of the solvent
(c) One litre of the solution
(d) 22.4 litres of the solution

Ans. (c)

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Which one of the following properties of an element is not variable?
(a) Valency
(b) Atomic weight
(c) Equivalent weight
(d) All of these

Ans. (b)

The number of water molecules in 1 litre of water is
(a) 18
(b) 18 x 1000
(c) N_A
(d) 55.55 N_A

Ans. (d)

Find the number of gram molecules of hydrogen present in 1 gram molecule of methane gas.
(a) 1
(b) 2
(c) 4
(d) 8

Ans. (b)

The types of forces that holds the atoms together in a molecule is
(a) Covalent bonds
(b) Ionic bonds
(c) Gravitational force
(d) Magnetic forces

Ans. (a)

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The numbers of moles of BaCO₃ which contain 1.5 moles of oxygen atoms is
(a) 0.5
(b) 1
(c) 3
(d) 6.02 x 10²³

Ans. (a)

The modern atomic weight scale is based on
(a) C¹²
(b) O¹⁶
(c) H¹
(d) C¹³

Ans. (a)

The weight of 1 gram atom of sulphur is
(a) 32 amu
(b) 32 grams
(c) 16 amu
(d) 16 grams

Ans. (b)

Number of molecules in 100 ml of each of O₂, NH₃ and CO₂ at STP are
(a) In the order CO₂ < O₂ < NH₃
(b) In the order NH₃ < O₂ < CO₂(c) The same
(d) NH₃ = CO₂ < O₂

Ans. (c)

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The number of atoms present in a molecule is called its atomicity. Then, the atomicity of phosphorus and sulphur is _____ and _____ respectively.
(a) 1, 2
(b) 3, 6
(c) 2, 4
(d) 4, 8

Ans. (d)

The total number of protons in 10 g of calcium carbonate is (N₀ = 6.023 x 10²³)
(a) 1.5057 x 10²⁴
(b) 2.0478 x 10²⁴(c) 3.0115 x 10²⁴
(d) 4.0956 x 10²⁴

Ans. (c)

The weight of 1/4 mole of calcium atom =
(a) 40 grams
(b) 20 grams
(c) 10 grams
(d) 5 grams

Ans. (c)

The total number of gm-molecules of SO₂Cl₂ in 13.5 g of sulphuryl chloride is
(a) 0.1
(b) 0.2
(c) 0.3
(d) 0.4

Ans. (a)

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The symbol of carbon is C. It means that
(a) ‘C’ represents one atom of carbon.
(b) ‘C’ also represents 1 mole of carbon atoms.
(c) ‘C’ also represents 12g of C.
(d) All

Ans. (d)

The largest number of molecules is in
(a) 34 g of water
(b) 28 g of CO₂
(c) 46 g of CH₃OH
(d) 54 g of N₂O₅

Ans. (a)

The weight of 1/4 mole of atom of an element is 5 grams. Identify the substance
(a) Boron
(b) Neon
(c) Phosphorus
(d) Calcium

Ans. (b)

Which of the following exists in mono-atomic form?
(a) He
(b) Ne
(c) Ar
(d) All

Ans. (d)

2g of oxygen contains number of atoms equal to that in
(a) 0.5 g of hydrogen
(b) 4g of sulphur
(c) 7g of nitrogen
(d) 2.3 g of sodium

Ans. (b)

The mass of one atom of an unknown element is 4 x 1.66 × 10^–24g. The element is
(a) Hydrogen
(b) Helium
(c) Oxygen
(d) Sulphur

Ans. (b)

The weight of 1 molecule of a substance is 98 amu. The substance is
(a) Calcium carbonate
(b) Sulphuric acid
(c) Sodium chloride
(d) Phosphoric acid

Ans. (b)

, (d)

One mole of calcium phosphide on reaction with excess of water gives
(a) One mole of phosphine
(b) Two moles of phosphoric acid
(c) Two moles of phosphine
(d) One mole of phosphorus pentoxide

Ans. (c)

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The gram atomic weight of oxygen is
(a) 16 amu
(b) 16 g
(c) 32 amu
(d) 32 g

Ans. (b)

Molarity of liquid HCl with density equal to 1.17 g / cc is
(a) 36.5
(b) 18.25
(c) 32.05
(d) 4.65

Ans. (c)

Which of the following contains same number of molecules as in 1 mole of any substance?
(a) 32 g of sulphur
(b) 18 g of H2O
(c) 17 g of ammonia
(d) 16 g of methane

Ans. (b)

, (c), (d)

The number of oxygen atoms in 4.4 g of CO₂is approx.
(a) 1.2 x 10²³
(b) 6 x 10²²(c) 6.2 x 10²²
(d) 12 x 10²³

Ans. (a)

The ratio of number of molecules present in 1 gram mole of O2 to one gram mole of SO₂ is
(a) 1 : 4
(b) 1 : 2
(c) 1 : 8
(d) 1 : 1

Ans. (d)

12 g of Carbon contains equal number of atoms as
(a) 12 grams of Mg
(b) 40 grams of Calcium
(c) 32 grams of Oxygen
(d) 7 grams of nitrogen

Ans. (a)

The number of moles of sodium oxide in 620 g of it is
(a) 1 mole
(b) 10 moles
(c) 18 moles
(d) 100 moles

Ans. (b)