Atoms and Molecules Test

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Atoms and Molecules Test - 50

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following is a merit of Dalton's atomic theory?

A
Laws of chemical combination

B
The distinction between the fundamental particle of an element (atom) and that of a compound (molecule)

C
Both A and B

D
None of the above

Solution

Dalton's theory explains the laws of chemical combinations. Dalton was the first person to recognize a workable difference between the fundamental particle of an element (atom) and that of a compound (molecule).
So both the statements are correct.
Option $$C$$ is correct.
Question 2
1 / -0

Which of the following explains Democritus' atomic model?

A

B

C

D
None of the above

Solution

Democritus' atomic model (option B) was simply a round sphere with no electrons, protons, or neutrons. Democritus created the first atomic model. His contribution helped people with understanding the idea of an atom, and helped other scientists further look into the science of the atom and its generic makeup.

Option A is Thomson's atomic model, and option C is Rutherford's atomic model.
Question 3
1 / -0

Ionic species with a positive charge called as :

A
cation

B
inert Gas

C
crystal

D
anion

E
element

Solution

Ionic species with a positive charge are called cations.
Cations form when an element or group of elements(compounds) lose one or more electrons. Cations can be formed from metal elements, as well as nonmetal elements. If a metal element forms an ion, it always forms a cation. Some metals always form the same type of cation. For example, sodium always forms a $$+1$$ cation ($$Na^+$$) and magnesium always forms a $$+2$$ cation $$(Mg^{2+})$$.
Question 4
1 / -0

Find the best option among the following about the simplest unit of water that retains its properties :

A
A molecule

B
A mixture of compounds

C
An isotope

D
An isomer

E
An acid salt

Solution

A molecule is a group of two or more atoms that form the smallest identifiable unit into which a pure substance can be divided and still retain the composition and chemical properties of that substance.
Thus, from a structural point of view, a molecule consists of an aggregation of atoms held together by valence forces. So, the simplest unit of water that retains its properties is a molecule.

Hence option $$A$$ is correct.
Question 5
1 / -0

What is the approximate mass of $$Ca(NO_3)_2$$?
(Given- Atomic mass of $$Ca = 40, N = 14, O = 16$$)

A
$$70$$

B
$$82$$

C
$$102$$

D
$$150$$

E
$$164$$

Solution

The approximate mass of $$\displaystyle Ca(NO_3)_2$$ $$=\displaystyle 40 + 2 \times [14 + (3 \times 16)] = 40 + 2 \times (14+48)
= 40 + 2 \times 62 = 40+124=164$$.
Question 6
1 / -0

Total how many atoms are present in the formula $$Ca_3(PO_4)_2$$?

A
$$5$$

B
$$8$$

C
$$9$$

D
$$12$$

E
$$13$$

Solution

Following atoms are present in the given formula:

Ca = 3 atoms
P = 2 atoms
O = (4$$\times 2$$) 8 atoms

Total number of atoms present in the formula = 3 + 2 + 8 = 13.
Question 7
1 / -0

Total number of atoms present in the formula $$Na_2CO_3$$ is :

A
$$1$$

B
$$6$$

C
$$9$$

D
$$10$$

E
$$14$$

Solution

Atom of Na - 2
Atom of C - 1
Atoms of O - 3
Thus, total number of atoms present in $$Na_2CO_3=6$$.
Hence the correct option is $$B$$.
Question 8
1 / -0

All of the following are compounds except :

A
copper sulfate

B
carbon dioxide

C
washing soda

D
air

E
lime

Solution

All are compounds except Air which is a mixture of various gases in definite proportion.

Hence, the correct option is $$D$$.
Question 9
1 / -0

The molar mass of $$\displaystyle Al{ Cl }_{ 3 }$$ is:

A
$$67.9$$ g/mol

B
$$106.5$$ g/mol

C
$$62.5$$ g/mol

D
$$133.5$$ g/mol

Solution

Atomic mass of Al = $$27\ u$$

Atomic mass of Cl = $$35.5\ u$$

Molar mass of $$AlCl_3$$ = $$27+3 (35.5)=133.5$$ g/mol

Hence, the correct option is $$\text{D}$$.
Question 10
1 / -0

One atomic mass unit is equal to?

(Given, mass of one carbon-12 atom $$= 1.992 \times 10^{-23}$$)

A
$$1.66\times 10^{-27}g$$

B
$$1.66\times 10^{-24}g$$

C
$$1.66\times 10^{-23}g$$

D
$$1.66\times 10^{-25}g$$

Solution

One atomic mass unit (amu or u) is equal to 1/12th of the mass of an atom of carbon-12.

Mass of an atom of carbon-12 $$= 1.992 \times 10^{-23}\ g$$

1 amu $$=$$ 1/12 mass of carbon-12 atom $$= \dfrac {1}{12} \times 1.992 \times 10^{-23}$$ $$= 1.66\times 10^{-24}g$$

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Re-Attempt Weekly Quiz Competition

Atoms and Molecules Test - 50

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Atoms and Molecules Test - 50

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SHARING IS CARING

Question 1

Laws of chemical combination

The distinction between the fundamental particle of an element (atom) and that of a compound (molecule)

Both A and B

None of the above

Solution

Question 2

None of the above

Solution

Question 3

cation

inert Gas

crystal

anion

element

Solution

Question 4

A molecule

A mixture of compounds

An isotope

An isomer

An acid salt

Solution

Question 5

$$70$$

$$82$$

$$102$$

$$150$$

$$164$$

Solution

Question 6

$$5$$

$$8$$

$$9$$

$$12$$

$$13$$

Solution

Question 7

$$1$$

$$6$$

$$9$$

$$10$$

$$14$$

Solution

Question 8

copper sulfate

carbon dioxide

washing soda

air

lime

Solution

Question 9

$$67.9$$ g/mol

$$106.5$$ g/mol

$$62.5$$ g/mol

$$133.5$$ g/mol

Solution

Question 10

$$1.66\times 10^{-27}g$$

$$1.66\times 10^{-24}g$$

$$1.66\times 10^{-23}g$$

$$1.66\times 10^{-25}g$$

Solution

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