Quiz – Mole Concept and Stoichiometry

QUIZ - Problems / Numericals based on Mole Concept (Atomic Mass/ Molar Mass/ Avogadro number)

Quiz based on -https://freakgenie.com/problems-numericals-based-on-mole-concept/

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Mass = Molar mass x Number of moles

Number of particles = Number of moles x Avogadro number

1 / 8

Calculate the number of formula units in 177 g PbCr

$O_{4}$

. (Pb = 206, Cr = 52, O = 16, S = 32, Avogadro number = No)

0.50 No formula units

1.0 No formula units

1.5 No formula units

2.0 No formula units

Mass = Molar mass x Number of moles

177.0 g = 354 g ${mol}^{- 1}$ x Number of moles

or Number of moles = 0.50 mol

Number of particles = Number of moles x Avogadro number

or Number of particles = 0.50 x No formula units

Mass = Molar mass x Number of moles

Number of particles = Number of moles x Avogadro number

Note that if it is not mention atom or molecule before mole, it always means one mole of that substance in its natural form.

2 / 8

Calculate the number of molecules in 68.0g of

${NH}_{3}$

. (N = 14, H = 1, Avogadro number = No)

3 No

4 No

5 No

6 No

Mass = Molar mass x Number of moles

68.0 g = 17.0 g ${mol}^{- 1}$ x Number of moles

Number of moles = 4.0 mol ammonia molecules

Number of particles = Number of moles x Avogadro number

Number of particles = 4.0 x No

Problem based on formula no. – 2
Number of moles = Given number of particles / Avogadro number
Calculation of mole from number of particles and vice – versa.

3 / 8

Calculate the moles of

$3.01 x 10^{23}$

bromine atoms. (Br = 80).

0.30 mol Br molecules

0.25 mol Br atoms

0.50 mol Br molecules

0.50 mol Br atoms

Number of moles = Given number of particles / Avogadro number
$= \frac{3.01 x 10^{23}}{6.02 x 10^{23}} = 0.50 m o l Br a t o m s$

Problem based on formula no. – 1
Mass = Molar mass x Number of moles
Calculation of mass from mole of any fundamental unit like atom, molecule and vice – versa.

4 / 8

Calculate the number of moles in 40.0 g

$B r_{2}$

(Br = 80).

0.50 mol Br molecules

0.50 mol Br atoms

0.25 mol Br molecules

0.25 mol Br atoms

Atomic mass = 80 g ${mol}^{- 1}$
Molecular mass = 160 g ${mol}^{- 1}$
moles = mass / molar mass =
$\frac{40 g}{160 g m o l^{- 1}} = 0.25 m o l {Br}_{2} molecules$

Problem based on formula no. – 3
Number of particles =
$\frac{G i v e n m a s s}{m o l a r m a s s}$
x Avogadro number
Calculation of number of particles from mass and vice – versa.

5 / 8

Calculate the mass of

$6.02 x 10^{25}$

sodium atoms. (Na = 23).

2.3 Kg Na molecules

2.3 Kg Na atoms

2.3 g Na molecules

2.3 g Na atoms

Atomic mass = 23 g ${mol}^{- 1}$
Number of particles = $\frac{G i v e n m a s s}{M o l a r m a s s}$ x Avogadro number
$6.02 x 10^{25} = \frac{G i v e n m a s s}{23 g m o l^{- 1}} x 6.02 x 10^{23} = 2.3 k g N a a t o m s$

Problem based on formula no. – 1
Mass = Molar mass x Number of moles
Calculation of mass from mole of any fundamental unit like atom, molecule and vice – versa.

6 / 8

Calculate the number of moles in 4Kg

${Na}_{11}^{23}$

(Na = 23).

173.9 mol Na molecules

173.9 mol Na atoms

1.739 mol Na molecules

17.39 mol Na atoms

Atomic mass = 23 g
${mol}^{- 1}$
moles = mass / Atomic mass =
$\frac{4.0 \times 10^{3} g}{23 g m o l^{- 1}} = 173.9 m o l N a a t o m s$

Problem based on formula no. – 1
Mass = Molar mass x Number of moles
Calculation of mass from mole of any fundamental unit like atom, molecule and vice – versa.
Note that if it is not mention atom or molecule before mole, it always means one mole of that substance in its natural form.

7 / 8

What is the mass of 5 moles of iron?

280 g Fe

140 g Fe

560 g Fe

Problem based on formula no. – 1
Mass = Molar mass x Number of moles
Calculation of mass from mole of any fundamental unit like atom, molecule and vice – versa.

8 / 8

How many moles of hydrogen (H₂) in 20 g of the gas?

10 mol Hydrogen molecules

20 mol Hydrogen atoms

both

none

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Quiz – Mole Concept and Stoichiometry – 1

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