Mole Concept Test

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Mole Concept Test - 6

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Weekly Quiz Competition

Question 1
1 / -0

The ratio by mass of magnesium and sulphur in magnesium sulphide is

A
5 : 2

B
3 : 4

C
1 : 2

D
2 : 1

Solution

Atomic mass of Mg = 24 g
Atomic mass of S = 32 g
Ratio of Mg and S in MgS = 24 : 32 = 3 : 4
Question 2
1 / -0

The atomic mass of zinc is 65.37 u. Which of the following is the correct weight of 1 atom of zinc?

A
9.21 x 10²¹ grams

B
1.08 x 10^-22grams

C
1.08 x 10²² grams

D
10.85 x 10²¹grams

E
0.09 x 10^-²² grams

Solution

1 mole of atoms = Gram atomic mass
Therefore, 65.37 g of zinc = 1 mole of zinc = 6.022 x 10²³ atoms of Zn.
6.022 x 10²³ atoms of Zn = 65.37 g
1 atom of Zn = 65.37/(6.022 x 10²³) g = 1.08 x 10^-22 g.
Question 3
1 / -0

What is the correct number of hydrogen atoms in 0.25 mole of water?

A
2

B
12.05 x 10²³

C
0.18 x 10²³

D
3.01 x 10²³

E
0.75 x 10²³

Solution

1 mole of H₂O contains 2 moles of H atoms.
= 2 X 6.023 x 10²³ hydrogen atoms
So, 0.25 mole of H₂O contains 2 x 6.023 x 10²³ x 0.25 H atoms.
= 3.01 x 10²³ H atoms.
Thus, this is the correct answer.
Question 4
1 / -0

Which of the following statements is/are correct?

(a) The word "mole" was introduced in 1896 by Wilhelm Ostwald.
(b) The mass of 1 mole of a substance is equal to its relative atomic or molecular mass in grams.
(c) The quantity of a substance can be characterised by the valency of its molecules.

A
(a) only

B
(b) only

C
(c) only

D
(a) and (b)

E
(a), (b) and (c)

Solution

Both the statements (a) and (b) are correct.
As, (a) The word "mole" was introduced around 1896 by Wilhelm Ostwald who derived the term from the Latin word moles meaning a 'heap' or 'pile`.
(b) Avogadro`s number is a proportion that relates molar mass on an atomic scale to physical mass on a human scale. Avogadro`s number is defined as the number of elementary particles (molecules, atoms, compounds, etc.) per mole of a substance. It is equal to 6.022 x 10²³ mol^-1 and is expressed as the symbol N_A.
Question 5
1 / -0

Which of the following statements is/are correct?

(a) Naturally occurring oxygen is a mixture of atoms of slightly different masses called isotopes.
(b) Formula mass is used instead of molecular mass for a substance whose constituent particles are ions.
(c) Basic radicals carry negative charge.

A
(a) only

B
(b) only

C
(c) only

D
(a) and (b)

E
(b) and (c)

Solution

This is the correct answer as both these statements are correct. Isotopes are same elements having different atomic mass but same atomic number. For example naturally occurring oxygen is composed of three stable isotopes, ¹⁶O, ¹⁷O, and ¹⁸O and Formulas Mass is a term used for the mass of a unit cell of an ionic compound that is essentially bound to all the other ions around it.
Question 6
1 / -0

Fluoride ion is a monovalent anion because it is a negative ion having a valency of one minus. Which of the following is also a monovalent anion?

A
Iodide ion

B
Oxide ion

C
Nitride ion

D
Sulphide ion

E
Phosphate ion

Solution

This is the correct option. Iodide ion is a monovalent anion.
Question 7
1 / -0

How many moles are there in 8 g of calcium? (Atomic mass of calcium = 40 u)

A
0.4

B
5

C
0.1

D
0.2

E
320

Solution

1 mole of atoms = Gram atomic mass

So, 1 mole of calcium atoms = Gram atomic mass of calcium = 40 g

Now, 40 g of calcium = 1 mole of calcium

So, 8 g of calcium = mole = 0.2 mole

Thus, there are 0.2 mole in 8 g of calcium.
Question 8
1 / -0

Calculate the number of iron atoms in a bar of iron weighing 8 g.

(Atomic mass of iron = 56 u)

A
8.602 x 10²² atoms

B
8.602 x 10²³ atoms

C
42.154 x 10²³ atoms

D
0.8602 x 10²⁰ atoms

E
1.344 x 10²¹ atoms

Solution

Number of atoms =
8 g of iron contains =
= 8.602 x 10²² atoms
Question 9
1 / -0

In a scientific experiment conducted in a controlled environment, 0.95 ml mixture of 'W' and 'A' was found to contain 0.57 ml of 'A' and 0.38 ml of 'W' respectively. Calculate the percentage composition of 'A' by volume.

A
0.60%

B
50%

C
60%

D
55%

E
1.67%

Solution

Here, mass of A in the mixture = 0.57 ml

Mass of the mixture = 0.95 ml

Thus, percentage of A =

= = 60%

Thus, it is the correct option.
Question 10
1 / -0

Which of the following statements is/are false?

(a) Mole is a link between the mass of atoms and the number of atoms.
(b) The number 6.023 10²³, which represents a mole, is known as Avogadro's number.
(c) An atom represents the amount of a substance equal to its gram atomic mass.

A
Only (a)

B
Only (a) and (b)

C
Only (c)

D
Only (b) and (c)

E
Only (b)

Solution

Gram atomic mass (GAM) is the mass of one mole of atoms of the substance and not the mass of one atom.
Both the atomic mass and the gram atomic mass are equal in magnitude. However, the unit for atomic mass is 'u' and that for GAM is 'g'.
Question 11
1 / -0

Anurag was asked by his teacher to convert 18.066 x 10²² molecules of element X into moles. What will be the correct answer?

A
0.2 mole

B
3.34 moles

C
0.4 mole

D
0.3 mole

E
3 moles

Solution

Here, 6.022 x 10²³ molecules of X = 1 mole

So, 18.066 x 10²² molecules of X =

= 0.3 mole
Question 12
1 / -0

The mass of a single atom of an element 'A' is 3.95 x 10^-23g. What is its atomic mass?

A
23.79 u

B
21.79 u

C
0.65 u

D
18.24 u

E
1.53 u

Solution

The atomic mass of an element is numerically equal to the mass of 1 mole of its atoms.
The mass of one atom of an element A = 3.95 x 10^-23 g
We know that 1 mole of an atom = 6.023 x 10²³ atoms
1 mole of an atom = its atomic mass
Mass of one atom of an element A = 3.95 x 10^-23 g
Mass of 6.023 x 10²³ atoms of an element A = 3.95 x 10^-23 x 6.023 x 10²³ = 23.79 u
Question 13
1 / -0

Element 'X' and element 'Y' combine in the ratio of 2 : 3 by mass to form 'Z'. In order to conduct an experiment, what mass of 'Y' would be required to react completely with 6 g of 'X'?

A
1 g

B
8 g

C
9 g

D
4 g

E
10 g

Solution

Here, we have been given X and Y to combine in a fixed ratio of 2 : 3 by mass.

2 g of X requires = 3 g of Y

So, 6 g of X requires = g of Y = 9 g of Y

Thus, it is the correct option.
Question 14
1 / -0

How many moles are there in 24.088 x 10²³ atoms of carbon?

A
4 moles

B
2 moles

C
0.25 moles

D
6 moles

E
5 moles

Solution

This is the correct option.

6.022 x 10²³ atoms of carbon = 1 mole

So, 24.088 x 10²³ atoms of carbon =

= 4 moles
Question 15
1 / -0

How many moles are there in 28 grams of nitrogen? (Atomic mass of nitrogen = 14 u)

A
5 moles

B
392 moles

C
4 moles

D
2 moles

E
0.5 mole

Solution

1 mole of atoms = gram atomic mass

So, 1 mole of nitrogen atoms = gram atomic mass of nitrogen = 14 g

Now, 14 g of nitrogen = 1 mole of nitrogen

Thus, 28 g of nitrogen = moles = 2 moles

Thus, there are 2 moles in 28 grams of nitrogen.
Question 16
1 / -0

How many moles are there in 54 g of water (H₂O)? (Atomic masses: H = 1 u; O = 16 u)

A
2 moles

B
972 moles

C
3 moles

D
4 moles

E
0.34 mole

Solution

Here, atomic mass of H is 1 u and that of O is 16 u. So, we have to first calculate the mass of 1 mole of H₂O using these values of atomic masses.

1 mole of H₂O = molecular mass of H₂O in grams

= Mass of H x 2 + Mass of O = 2 x 1 + 16 = 18 g
So, the mass of 1 mole of H₂O is 18 g.
Now, 18 g of H₂O = 1 mole
So, 54 g of H₂O = = 3 moles
Question 17
1 / -0

Which of the following contains the largest number of atoms?

A
11 g of CO₂

B
4 g of H₂

C
5 g of NH₃

D
8 g of SO₂

Solution

11 g of CO₂ = = 0.25 mole
4 g of H₂ = = 2 moles
5 g NH₃ = = 0.294 mole
8 g SO₂ = = 0.125 mole
One mole contains 6.022 x 10²³ particles. Therefore, the greater the number of moles, the greater the number of atoms.
Question 18
1 / -0

The number of atoms contained in 11.2 litres of SO₂ at NTP is

A
3/2 6.02 10²³

B
2 6.02 10²³

C
6.02 10²³

D
4 6.02 10²³

Solution

The number of moles of SO₂ = =
The number of molecules of SO₂= ^{The number of atoms in 1 molecule of SO₂= 3}Therefore, the number of atoms =
Question 19
1 / -0

How many moles of CO₂ are present in 2.50 10²⁴ molecules of CO₂?

A
4.15

B
2.15

C
1.15

D
0.15

Solution

6.02 x 10²³molecules of CO₂ = 1 mole of CO₂2.50 10²⁴ molecules of CO₂=
= 4.15 moles of CO₂
Question 20
1 / -0

If one mole of CO and one mole of O₂ are made to react at STP, what is the total number of moles at the end of the reaction?

A
1.5 moles

B
1 mole

C
4 moles

D
2 moles

Solution

The balanced chemical equation of the reaction between CO (g) and O₂ (g) is
2CO (g) + O₂ (g) 2CO₂ (g)
According to the equation,
The number of moles of CO₂formed = Number of moles of CO used = 1 mole
The number of moles O₂ required = 1/2 number of moles of CO used = 0.5 mole
The number of moles of O₂ left = 1 - 0.5 = 0.5 mole
The total number of moles at the end of the reaction = 1 mole of CO₂+ 0.5 mole of O₂ = 1.5 moles