Atoms and Molecules Test

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Atoms and Molecules Test - 45

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Weekly Quiz Competition

Question 1
1 / -0

The matter is neither created nor destroyed during any physical or chemical change. This statement is of the :

A
Law of constant proportion

B
Law of conservation of mass

C
Law of reciprocal proportion

D
Law of multiple proportion

Solution

The law of conservation of mass states that "the matter is neither created nor destroyed during any physical or chemical change".
The Law of conservation of Mass states that matter can be changed from one form into another, mixtures can be separated or made, and pure substances can be decomposed, but the total amount of mass remains constant. The total mass of the universe is constant within measurable limits.
Option $$B$$ is correct.
Question 2
1 / -0

Calculate the mass (in grams) of one molecule of $$CH_{3}COOH$$.
(Molar mass of $$CH_{3}COOH = 60.06\ g/ mol$$)

A
$$9.97\times 10^{-23}$$

B
$$60.06$$

C
$$9.97\times 10^{23}$$

D
None of above

Solution

The molar mass of $$CH_3COOH$$ is given as $$60.06\ g/mol$$

We need to find the mass of 1 molecule of $$CH_3COOH$$

We can use this formula: $$Number\ of\ atoms = \dfrac {mass} {molar\ mass} \times Avogadro\ number$$

We can substitute the following values in the formula:

$$Number\ of\ atoms = 1$$
$$Molar\ mass = 60.06\ g/mol$$
$$Avogadro\ no. = 6.022 \times 10^{23}$$

$$Number\ of\ atoms = \dfrac {mass} {molar\ mass} \times Avogadro\ number$$

$$\therefore 1 = \dfrac {mass} {60.06} \times 6.022 \times 10^{23}$$

$$mass = \dfrac {60.06} {6.022 \times 10^{23}}$$ $$= 9.973 \times 10^{-23}\ g$$
Question 3
1 / -0

When mass is enclosed in a system and no transfer of material and energy is allowed in or out, it's _____ will never change.

A
quality

B
quantity

C
temperature

D
shape

Solution

The law of conservation of mass states: Mass can neither be created nor destroyed in a chemical reaction. According to this law mass of an isolated system will remain constant over time. This means when mass is enclosed in a system and no transfer of material and energy is allowed in or out, its quantity will never change.
Question 4
1 / -0

In a compound, the ratio of the atoms or element by mass remains always the same irrespective of :

A
temperature

B
nature of compound

C
source of compound

D
size of compound

Solution

Compounds are formed by the combination of two or more elements. In a compound, the ratio of the atoms or element by mass remains always the same irrespective of the source of the compound. This means a certain compound always formed by the combination of atoms in the same ratio by mass. If the ratio of the mass of constituent atoms will be altered the new compound is formed.
Hence, option $$C$$ is correct.
Question 5
1 / -0

A solution of copper oxide was prepared by heating, igniting and precipitation. Which of the following method will give higher ratio of copper oxide?

A
Heating

B
Precipitation

C
Ignition

D
All of the above will give the same ratio

Solution

In a compound, the ratio of the atoms or element by mass remains always the same irrespective of the source of the compound. This means a certain compound is always formed by the combination of atoms in the same ratio by mass. Hence, copper oxide made from any method will always give the same ratio of copper oxide.
Question 6
1 / -0

If the ratio of the atoms by mass is altered then:

A
new compound formed

B
same compounds are formed

C
no reaction takes place

D
state of compounds are changed

Solution

In a compound, the ratio of the atoms or element by mass remains always the same irrespective of the source of the compound. This means a certain compound is always formed by the combination of atoms in the same ratio by mass. If the ratio of the mass of constituent atoms will be altered the new compound is formed.
Question 7
1 / -0

Dalton’s atomic theory was based on:

A
Law of chemical combination

B
Mass theory

C
Periodic table

D
None of the above

Solution

When substances react, they do so by following certain laws. These laws are called the laws of chemical combination. Law of conservation of mass, the law of definite proportions, the law of multiple proportions, Gay lussac's law of gaseous volumes, Avogadro's law. These formed the basis of Dalton's atomic theory of matter.

Dalton explained about atoms on the basis of the Laws of Chemical Combinations.

So, the correct option is $$A$$.
Question 8
1 / -0

The ratio of mass of nitrogen and oxygen in nitric oxide is:

A
$$7:16$$

B
$$1:8$$

C
$$7:8$$

D
$$7:15$$

Solution

The formula of nitric oxide is NO.

Mass of nitrogen in NO is 14 g.

Mass of oxygen is 16 g.

Therefore, ratio is 14:16 = 7:8.
Question 9
1 / -0

What are the merits of Dalton's atomic theory?

A
Explains laws of chemical combination

B
Explains the law of conservation of mass

C
Both A and B

D
Atoms can not be rearranged, combined or separated in a chemical reaction.

Solution

The atomic theory explains the laws of chemical combination (the Law of Constant Composition and the Law of Multiple Proportions) Dalton was the first person to recognize a workable distinction between the fundamental particle of an element (atom) and that of a compound (molecule).
Question 10
1 / -0

What is the molecular mass of $$C_2H_4?$$

A
$$26$$

B
$$14$$

C
$$28$$

D
$$16$$

Solution

Molecular mass of $$C_2H_4 = (2\times atomic\ mass\ of\ carbon )$$ $$+ (4\times atomic\ mass\ of\ hydrogen)$$
$$=(2\times 12)+(4\times 1)$$
$$=28$$
Option $$C$$ is correct.

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Atoms and Molecules Test - 45

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Atoms and Molecules Test - 45

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Question 1

Law of constant proportion

Law of conservation of mass

Law of reciprocal proportion

Law of multiple proportion

Solution

Question 2

$$9.97\times 10^{-23}$$

$$60.06$$

$$9.97\times 10^{23}$$

None of above

Solution

Question 3

quality

quantity

temperature

shape

Solution

Question 4

temperature

nature of compound

source of compound

size of compound

Solution

Question 5

Heating

Precipitation

Ignition

All of the above will give the same ratio

Solution

Question 6

new compound formed

same compounds are formed

no reaction takes place

state of compounds are changed

Solution

Question 7

Law of chemical combination

Mass theory

Periodic table

None of the above

Solution

Question 8

$$7:16$$

$$1:8$$

$$7:8$$

$$7:15$$

Solution

Question 9

Explains laws of chemical combination

Explains the law of conservation of mass

Both A and B

Atoms can not be rearranged, combined or separated in a chemical reaction.

Solution

Question 10

$$26$$

$$14$$

$$28$$

$$16$$

Solution

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