Atoms and Molecules Test

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Atoms and Molecules Test - 57

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Weekly Quiz Competition

Question 1
1 / -0

The charge on 1 gram of $$Al^{3+}$$ ions is (e=electronic charge):

A
$$\dfrac{1}{27}N_Ae\, coulomb$$

B
$$\dfrac{1}{3}N_Ae\, coulomb$$

C
$$\dfrac{1}{9}N_Ae\, coulomb$$

D
$$ 3\, N_Ae\, coulomb$$

Solution

769481

1. $$\cfrac{1}{9}$$ NA e coulombs

2. So for finding the charge of one gram ion of $$Al^{3+}$$, We have to know that

1 gm atom = 1 mole of atom

So, charge on one mole of electron = $$N_a \times$$ charge on $$1 e^⁻$$

$$= 6.023 \times 10²^{23} \times 1.6 \times 10^{-19} C$$.

$$=9.6368 \times 10^4 (N_ae^⁻)$$

Thus, Charge on one mole of $$Al^{3+}$$ ion $$= 3 \times 96368$$

$$= 289104 C ( or 3 N_a e^⁻ )$$

Since , 27 g of $$Al^{3+}$$ ion having charge of 289104 C .

Therefore, 1 g of $$Al^{3+}$$ ion having charge = $$\cfrac{289104}{ 27}$$ C.

$$=10707.5 C. (or\cfrac{ N_a e^⁻}{ 9} )$$
Question 2
1 / -0

Which symbol is used to represent the unit of atomic mass, amu?

A
u

B
A

C
M

D
n

Solution

The symbol 'u' represents the unit of atomic mass, amu. For example, the atomic mass of carbon-12 is written as 12 u.
Hence, option A is correct.
Question 3
1 / -0

4.88 g of $$KClO_3$$ when heated produced 1.92 g of $$O_2$$ and 2.96 g of KCl. Which of the following statements regarding the experiment is correct?

A
The result illustrates the law of conservation of mass.

B
The result illustrates the law of multiple proportions.

C
The result illustrates the law of constant proportion.

D
None of the above laws is being illustrated here.

Solution

$$2KClO_3 \rightarrow 2KCl+3O_2$$
Mass of the reactant = total mass of the products ($$2.96 + 1.92=4.88\ g$$)
According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants. Therefore, this demonstrates the law of conservation of mass.
Option A is correct
Question 4
1 / -0

Decreasing order of atomic weight is correct of the elements given below?

A
$$Fe > Co > Ni$$

B
$$Ni > Co > Fe$$

C
$$Co > Ni > Fe$$

D
$$Co > Fe > Ni$$

Solution

Atomic weight of Iron $$\approx 56$$ u
Atomic weight of Cobalt $$\approx 59$$ u
Atomic weight of Nickel $$\approx 58.7$$ u
So, the order of atomic weights is $$Co>Ni>Fe$$.
Option $$C$$ is correct.
Question 5
1 / -0

The number of electrons which will together weight one gram is :

A
$$1.098 \times 10^{27}$$electrons

B
$$9.1096\times 10^{31} $$ electrons

C
$$1$$ electron

D
$$1\times 10^4 $$ electrons

Solution

Mass of one electron $$= 9.1096 \times 10^{−31}$$ kg

Number of electrons $$\times$$ mass of 1 electron $$= 1 g = 10^{−3} kg$$

$$N \times 9.1096 \times 10^{−31}=10^{-3}$$

$$N=\frac{10^{−3}}{9.1096 \times 10^{−31}}$$

$$N= 1.098 \times 10^{27}$$ electrons

Option A is correct
Question 6
1 / -0

How many moles of oxygen gas can be produced during electrolytic decomposition of $$180 \ g$$ of water?

A
2.5 moles

B
5 moles

C
10 moles

D
7 moles

Solution

Water decomposition can be represented as:

$$2H_2O \rightarrow 2H_2+O_2$$

$$2$$ moles (or $$2\times 18=36$$ g) of water gives one mole of oxygen.

$$180$$ g water will produce $$\dfrac{180}{36}$$ mol of oxygen $$=5$$ mol of oxygen.

Hence, option $$B$$ is correct.
Question 7
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Which of the following statements about a compound is incorrect?

A
A molecule of a compound has atoms of different elements.

B
A compound cannot be separated into its constituent elements by physical methods of separation.

C
A compound retains the physical properties of its constituent elements.

D
The ratio of atoms of different elements in a compound is fixed.
Solution
Explanation:
Properties of compounds:
A molecule of a compound has atoms of different elements.
A compound cannot be separated into its constituent elements by physical methods of separation.
The ratio of atoms of different elements in a compound is fixed.
A compound does not retain the physical properties of its constituent elements. Because when two or more elements get combined chemically, they form a new compound with new chemical and physical properties depending on the nature of bonding in the compound.
Hence, the correct answer is option $$C$$.
Question 8
1 / -0

How much copper is present in $$50\ g$$ of $$CuSO_4$$?

A
$$19.90\ g$$

B
$$39.81\ g$$

C
$$63.5\ g$$

D
$$31.71\ g$$

Solution

Molar mass of $$CuSO_4=63.5+32+4 \times 16=159.5$$g

159.5 g $$CuSO_4$$ contains 63.5 g Cu

50 g $$CuSO_4$$ will have $$=\cfrac{63.5}{159.5} \times 50=19.90g\ Cu$$
Question 9
1 / -0

Which of the following statements best explains the law of conservation of mass, concerning a chemical change?

A
100 g of water is heated to give steam.

B
A sample of $$N_2$$ gas is heated at constant pressure without any change in mass.

C
36 g of carbon combines with 32 g of oxygen to form 68 g of $$CO_2$$.

D
10 g of carbon is heated in vacuum without any change in mass.

Solution

According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants.
Among the given option only option C involves a chemical change/reaction as:
$$C+O_2 \rightarrow CO_2$$
$$m_{reactants}=m_{products}$$
$$36+32=68\ g$$
option C is the best demonstration of the law of conservation of mass.
Question 10
1 / -0

Fill in the blanks by choosing the correct options.

A
$$X= 6.023\times 10^{23}$$ moleccules
$$Y= 22.4L$$ at any pressure
$$Z=$$ Gram molecular mass

B
$$X= 6.023\times 10^{23}$$ atoms/moleccules
$$Y= 22.4L$$ at NTP
$$Z=$$ Gram atomic mass

C
$$X=6.023\times 10^{23}$$ atoms
$$Y= 22.4L$$ at any temperature
$$Z=1 $$ gram mole

D

$$X=6.023\times 10^{23}$$ particles
$$Y= 11.2L$$ at NTP
$$Z=$$ Molar volume

Solution

$$1$$ mole $$=6.023\times 10^{23}$$ atoms / molecules $$=X$$
$$1$$ mole = Molar volume $$=22.4\ L$$ at $$NTP$$ $$=Y$$
$$1$$ mole = Gram atomic mass or gram molecular mass $$=Z$$
Hence, option $$B$$ is correct.

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Atoms and Molecules Test - 57

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Atoms and Molecules Test - 57

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Question 1

$$\dfrac{1}{27}N_Ae\, coulomb$$

$$\dfrac{1}{3}N_Ae\, coulomb$$

$$\dfrac{1}{9}N_Ae\, coulomb$$

$$ 3\, N_Ae\, coulomb$$

Solution

Question 2

u

A

M

n

Solution

Question 3

The result illustrates the law of conservation of mass.

The result illustrates the law of multiple proportions.

The result illustrates the law of constant proportion.

None of the above laws is being illustrated here.

Solution

Question 4

$$Fe > Co > Ni$$

$$Ni > Co > Fe$$

$$Co > Ni > Fe$$

$$Co > Fe > Ni$$

Solution

Question 5

$$1.098 \times 10^{27}$$electrons

$$9.1096\times 10^{31} $$ electrons

$$1$$ electron

$$1\times 10^4 $$ electrons

Solution

Question 6

2.5 moles

5 moles

10 moles

7 moles

Solution

Question 7

A molecule of a compound has atoms of different elements.

A compound cannot be separated into its constituent elements by physical methods of separation.

A compound retains the physical properties of its constituent elements.

The ratio of atoms of different elements in a compound is fixed.

Solution

Question 8

$$19.90\ g$$

$$39.81\ g$$

$$63.5\ g$$

$$31.71\ g$$

Solution

Question 9

100 g of water is heated to give steam.

A sample of $$N_2$$ gas is heated at constant pressure without any change in mass.

36 g of carbon combines with 32 g of oxygen to form 68 g of $$CO_2$$.

10 g of carbon is heated in vacuum without any change in mass.

Solution

Question 10

$$X= 6.023\times 10^{23}$$ moleccules$$Y= 22.4L$$ at any pressure$$Z=$$ Gram molecular mass

$$X= 6.023\times 10^{23}$$ atoms/moleccules$$Y= 22.4L$$ at NTP$$Z=$$ Gram atomic mass

$$X=6.023\times 10^{23}$$ atoms$$Y= 22.4L$$ at any temperature$$Z=1 $$ gram mole

$$X=6.023\times 10^{23}$$ particles$$Y= 11.2L$$ at NTP$$Z=$$ Molar volume

Solution

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$$X= 6.023\times 10^{23}$$ moleccules
$$Y= 22.4L$$ at any pressure
$$Z=$$ Gram molecular mass

$$X= 6.023\times 10^{23}$$ atoms/moleccules
$$Y= 22.4L$$ at NTP
$$Z=$$ Gram atomic mass

$$X=6.023\times 10^{23}$$ atoms
$$Y= 22.4L$$ at any temperature
$$Z=1 $$ gram mole

$$X=6.023\times 10^{23}$$ particles
$$Y= 11.2L$$ at NTP
$$Z=$$ Molar volume