Atoms and Molecules Test

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Atoms and Molecules Test - 31

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Weekly Quiz Competition

Question 1
1 / -0

One a.m.u. or one 'u' is equal to :

A
$$1.66053892 10^{-27} kg$$

B
$$1.66053892 10^{-29} kg$$

C
$$1.23457656 10^{-27} kg$$

D
$$1.23457656 10^{-29} kg$$

Solution

One a.m.u.(atomic mass unit) or one 'u' is $$\dfrac{1}{12}$$ of the mass of one carbon-$$12$$ atom.
It is equal $$1.6605389210 \times 10^{-24} g $$ or $$1.6605389210 \times 10^{-27} kg$$.
Question 2
1 / -0

The modern atomic mass unit is based on the mass of :

A
C-12 isotope

B
hydrogen

C
oxygen

D
nitrogen

Solution

One a.m.u. or one 'u' is equal to $$1.66053892 10^{-24}\ g $$ or $$1.66053892 10^{-27}\ kg$$. It is equal to $$\dfrac{1}{12}$$ of the mass of an atom of carbon-12.

It is used as a standard. The masses of all other atoms are determined relative to the mass of an atom of carbon-12.
Question 3
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Atomic number (Z) of a neutral atom and mass number (A) of an atom are equal to:
(Here n = number of neutrons and p = number of protons):

A
Z = n and A = n+p

B
Z = e and A = n+e

C
Z = p and A = n+p

D
Z = n and A = p+e

Solution

The atomic number = Z = no. of protons = p
The mass no. = A = no. of protons (p) + no. of neutrons(n) = n + p
Question 4
1 / -0

The symbol for SI unit of mole is:

A
mol

B
mole

C
M

D
$$m$$

Solution

The symbol for SI unit of mole is mol. It is not represented by mole. M is the symbol for the molarity of the solution.
Question 5
1 / -0

The number of moles of '$$X$$ ' atoms in $$93$$ gm of 'X' are:
(Molecular Weight of $$X =31$$ g/mole)

A
$$3 $$

B
$$3.5 $$

C
$$4$$

D
$$2$$

Solution

As we know,
Number of moles of $$X$$$$ =w/Molecular \ Weight$$
So the number of moles of $$X$$ $$= \dfrac{93}{31} = 3$$
Question 6
1 / -0

The number of atoms in $$60$$ g of neon$$[Ne]$$ are:
(Molar mass of $$Ne=20$$ g/mole)

A
$$6 \times 6.022 \times 10 ^{23} $$ atoms

B
$$2 \times 6.022 \times 10 ^{23} $$ atoms

C
$$5 \times 6.022 \times 10 ^{23} $$ atoms

D
$$3 \times 6.022 \times 10 ^{23} $$ atoms
Question 7
1 / -0

What mass of $$Na$$ will contain $$6.023 \times 10^{23}$$ number of atoms?

A
$$23$$ g

B
$$46$$ g

C
$$6.023$$ g

D
$$11.5$$ g

Solution

One mole of each substance contains $$N_A = 6.023\times10^{23}$$ atoms. Here $$N_A$$ = Avogadro number.
Mass of one mole of atoms = Molar mass
So, the mass of one mole of $$Na$$ = $$23$$ g = $$6.023 \times 10^{23}$$ number of atoms. (Atomic mass of $$Na$$ = $$23$$ u and molar mass is numerically equal to the atomic mass)
Hence, option A is correct.
Question 8
1 / -0

The number of potassium atoms present in $$117$$ g of potassium sample (Molecular Weight $$= 39$$ g/mole) is:

A
$$9 \times 6.023 \times 10 ^{23} $$ atoms

B
$$7 \times 6.023 \times 10 ^{23} $$ atoms

C
$$4 \times 6.023 \times 10 ^{23} $$ atoms

D
$$3 \times 6.023 \times 10 ^{23} $$ atoms

Solution

As we know, one mole of each substance contains $$N_A = 6.023\times10^{23}$$ atoms.
Here, moles of $$K$$ $$=\dfrac{117}{39} = 3$$
$$\therefore$$ atoms of $$K$$ $$=3 N_A = 3\times6.023\times10^{23}$$ atoms
Hence, option D is correct.
Question 9
1 / -0

A/An______ is the smallest particle of a substance which can take part in a chemical reaction.

A
atom

B
molecule

C
both A and B

D
none of the above

Solution

An atom is the smallest particle of a substance which can take part in a chemical reactions.
Question 10
1 / -0

The mass of one molecule of compound $${C}_{60}{H}_{122}$$ is :

A
$$1.3\times {10}^{-20}g$$

B
$$5.01\times {10}^{-21}g$$

C
$$3.72\times {10}^{-23}g$$

D
$$1.4\times {10}^{-21}g$$

Solution

Mass of one molecule of $${C}_{60}{H}_{122} =60\times C+122\times H= (12\times 60)+122\quad amu$$
   $$=842\ amu$$ ($$1amu = 1.66\times {10}^{-24}g$$)
(Atomic Mass Unit (amu): The atomic mass unit (amu) is equal to one twelfth of the mass of one atom of carbon-12 isotope.)
   $$=842\times 1.66\times {10}^{-24}g$$
   $$=1.4\times {10}^{-21}g$$

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Atoms and Molecules Test - 31

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Atoms and Molecules Test - 31

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Question 1

$$1.66053892 10^{-27} kg$$

$$1.66053892 10^{-29} kg$$

$$1.23457656 10^{-27} kg$$

$$1.23457656 10^{-29} kg$$

Solution

Question 2

C-12 isotope

hydrogen

oxygen

nitrogen

Solution

Question 3

Z = n and A = n+p

Z = e and A = n+e

Z = p and A = n+p

Z = n and A = p+e

Solution

Question 4

mol

mole

M

$$m$$

Solution

Question 5

$$3 $$

$$3.5 $$

$$4$$

$$2$$

Solution

Question 6

$$6 \times 6.022 \times 10 ^{23} $$ atoms

$$2 \times 6.022 \times 10 ^{23} $$ atoms

$$5 \times 6.022 \times 10 ^{23} $$ atoms

$$3 \times 6.022 \times 10 ^{23} $$ atoms

Question 7

$$23$$ g

$$46$$ g

$$6.023$$ g

$$11.5$$ g

Solution

Question 8

$$9 \times 6.023 \times 10 ^{23} $$ atoms

$$7 \times 6.023 \times 10 ^{23} $$ atoms

$$4 \times 6.023 \times 10 ^{23} $$ atoms

$$3 \times 6.023 \times 10 ^{23} $$ atoms

Solution

Question 9

atom

molecule

both A and B

none of the above

Solution

Question 10

$$1.3\times {10}^{-20}g$$

$$5.01\times {10}^{-21}g$$

$$3.72\times {10}^{-23}g$$

$$1.4\times {10}^{-21}g$$

Solution

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