Some Basic Concepts of Chemistry Test

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Some Basic Concepts of Chemistry Test - 35

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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 percent composition of carbon in $$C_6H_{12}O_6$$ :

A
$$50%$$

B
$$40%$$

C
$$35.3%$$

D
$$22.1%$$

Solution

Molar mass of compound $$: 6(12.0)+12(1.01)+6(16.0)=180g/mol$$
Mass due to carbon $$=6(12.0)=72.06g/mol$$
$$%$$ composition of $$C=72/180\times 100=40%$$
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

What is the percent of composition of the compound that forms when $$222.7g$$ of N combines compleletly with $$77.4g$$ of O?

A
$$70%, 30%$$

B
$$80%, 20%$$

C
$$74.2%, 25.8%$$

D
$$72.2%, 27.8%$$

Solution

The mass composition$$:$$
Total mass$$: 222.7+77.4=300.1$$
Mass percentage of N$$:$$
$$222.7300.1=74.25$$
Mass percentage of O$$:$$
$$100-74.2=25.8%$$
Question 5
1 / -0

Which of the following statement is incorrect for the composition of water?

A
For water, the gravimetric or mass ratio of hydrogen to oxygen is $$1:8$$

B
In water, the ratio of hydrogen and oxygen is $$2:1$$ by volume

C
The ratio in which hydrogen and oxygen combine gives the composition of water.

D
None of the above

Solution

All of the following statements are correct for the composition of water.
A
For water, the gravimetric or mass ratio of hydrogen to oxygen is 1:8.
B
In water, the ratio of hydrogen and oxygen is 2:1 by volume.
C
The ratio in which hydrogen and oxygen combine gives the composition of water.
Note:
$$2H_2 + O_2 \rightarrow 2H_2O$$
Thus, the composition of water is $$H : O = 2: 1 $$
It is the ratio in which hydrogen and oxygen combine. The atomic masses of H and O are 1 and 16 respectively. Hence, for water, the gravimetric or mass ratio of hydrogen to oxygen is 2:16 or 1:8.
In water, the ratio of hydrogen and oxygen is 2:1
by volume. It is equal to the ratio in which hydrogen and oxygen combine.
Question 6
1 / -0

A mixture contains $$2.5$$g $$CaCO_3$$ and $$3.0$$g $$NaCl$$. What is the percent by mass of $$CaCO_3?$$

A
$$45.45$$

B
$$75$$

C
$$53$$

D
$$60$$

Solution

Total mass$$=2.5+3.0g=5.5g$$

$$\%$$ by mass $$CaCO_3=\dfrac{2.5}{5.5}\times 100 = 45.45\%$$
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

One volume of nitrogen combines with one volume of oxygen to form two volumes of nitric oxide. Calculate the amount of each reactant required to produce 250 ml of nitric oxide.

A
$$N_2=100 ml, O_2=100 ml$$

B
$$N_2=120 ml, O_2=120 ml$$

C
$$N_2=125 ml, O_2=125 ml$$

D
$$N_2=100 ml, O_2=125 ml$$

Solution

$$N_2+O_2\longrightarrow 2NO$$
1 ml of $$N_2$$ reacts with 1 ml of $$O_2$$ to produce 2 ml of $$NO$$.
So, to produce 250 ml of $$NO$$, 125 ml of $$N_2\ $$and$$\ O_2$$ are required.
Question 9
1 / -0

When two molecules of hydrogen react with one molecule of oxygen, the mass of reactants is $$36$$, what is the mass of products?

A
$$18$$

B
$$36$$

C
$$9$$

D
$$32$$

Solution

The Law of conservation of mass states that the total mass of reactants is equal to the total mass of products. In any chemical reaction, the total mass of the substance before and after the reaction is the same although its matter undergoes a physical change.

$$2H_2+O_2 \longrightarrow 2H_2O$$

Hence, the mass of the product i.e., water is $$36$$.
Question 10
1 / -0

Mass of beaker=20 g
Mass of beaker+mixture=50 g
Mass of washed and dried sand=5 g
Find the percentage of sand in the mixture.

A
16.67%

B
20%

C
25%

D
30%

Solution

Mass of mixture=$$50 g-20 g=30 g$$
Mass of washed and dried sand in the mixture=$$5g$$
Percentage=$$\frac{5}{30}\times 100$$
=16.67%

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Re-Attempt Weekly Quiz Competition

Some Basic Concepts of Chemistry Test - 35

Result

Some Basic Concepts of Chemistry Test - 35

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SHARING IS CARING

Question 1

Law of constant proportion

Law of conservation of mass

Law of reciprocal proportion

Law of multiple proportion

Solution

Question 2

$$50%$$

$$40%$$

$$35.3%$$

$$22.1%$$

Solution

Question 3

quality

quantity

temperature

shape

Solution

Question 4

$$70%, 30%$$

$$80%, 20%$$

$$74.2%, 25.8%$$

$$72.2%, 27.8%$$

Solution

Question 5

For water, the gravimetric or mass ratio of hydrogen to oxygen is $$1:8$$

In water, the ratio of hydrogen and oxygen is $$2:1$$ by volume

The ratio in which hydrogen and oxygen combine gives the composition of water.

None of the above

Solution

Question 6

$$45.45$$

$$75$$

$$53$$

$$60$$

Solution

Question 7

Law of chemical combination

Mass theory

Periodic table

None of the above

Solution

Question 8

$$N_2=100 ml, O_2=100 ml$$

$$N_2=120 ml, O_2=120 ml$$

$$N_2=125 ml, O_2=125 ml$$

$$N_2=100 ml, O_2=125 ml$$

Solution

Question 9

$$18$$

$$36$$

$$9$$

$$32$$

Solution

Question 10

16.67%

20%

25%

30%

Solution

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