Atoms and Molecules Test

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Atoms and Molecules Test - 32

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Weekly Quiz Competition

Question 1
1 / -0

A diatomic molecule is :

A
brass

B
graphite

C
silicon

D
nitrogen

Solution

Nitrogen gas is diatomic molecule as $$N_2$$ contains two atoms of nitrogen.
Question 2
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The number of nitrogen atoms in $$21$$ g of nitrogen are:
(Molecular Weight of Nitrogen $$=14$$ g/mole)

A
$$0.75$$$$N_A$$

B
$$1.5$$$$N_A$$

C
$$21$$$$N_A$$

D
$$14$$$$N_A$$

Solution

Number of moles of nitrogen $$ = \dfrac{21}{28} = 0.75$$
So, the number molecules of nitrogen $$0.75 N_A$$
The number of atoms of nitrogen $$\Rightarrow \ 2\times0.75 N_A = 1.5 N_A$$
Question 3
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Which of the following is a suitable example for illustrating the law of conservation of mass? (Atomic mass of O = 16 u; H = 1 u)

A
18g of water is formed by the combination of 16g oxygen with 2g of hydrogen.

B
18g of water in liquid state is obtained by heating 18g of ice.

C
18g of water is completely converted into vapour state on heating.

D
18g of water freezes at $$4^{o}C$$ to give same mass of ice.

Solution

According to law of conservation of mass
Mass of reactants $$=$$ Mass of products
$$H_2 + O_2\rightarrow 2H_2O$$
$$4 g$$ $$32 g$$ $$36 g$$
$$2 g$$ $$16 g$$ $$18 g$$
$$2g + 16g = 18 g$$
Therefore, correct option is $$A$$.
Question 4
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The molecular mass of $$CuSO_4.5H_2O$$ is:
(Atomic mass of $$Cu$$ $$=$$ 63.5, $$H$$ $$=$$ 1, $$O$$ $$=$$ 16, $$S$$ $$=$$ 32)

A
233.5 gm/mole

B
249.5 gm/mole

C
251.5 gm/mole

D
247.5 gm/mole

Solution

Molecular mass of a compound is the sum of atomic masses of each element present in the molecule.
Molecular mass $$=$$ atomic mass of $$Cu$$ + atomic mass of $$S$$ + (9 $$\times$$ atomic mass of $$O$$) + (10 $$\times$$ atomic mass of $$H$$) $$= 63.5+32+ 9 \times 16+10 \times 1 = 249.5\ gm/mole $$
Question 5
1 / -0

Which has a higher mass : 1 mole of $$CO_2$$ or 1 mole of $$CO?$$ (Mass of $$C=12,$$ Mass of $$O=16$$)

A
$$CO_2$$

B
$$CO$$

C
Both $$CO_2$$ and $$CO$$ have same mass

D
None of the above

Solution

As we know,
mass of one mole $$CO_2 = 44gm $$ i.e. $$( 12+ (2\times 16)$$
mass of one mole $$CO = 28gm$$ i.e. $$ ( 12+ 16)$$
Question 6
1 / -0

The molecular mass of $$(NH_4)_2CO_3$$ is:
Given atomic mass of H = 1, O = 16, C = 12, N = 14.

A
96 gm/mole

B
98 gm/mole

C
94 gm/mole

D
80 gm/mole

Solution

Molar mass
$$(NH_4)_2CO_3 = 2\times18+12+3\times16 = 96 gm/mole $$
Question 7
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Sodium chloride ($$NaCl$$) reacts with silver nitrate ($$AgNO_3$$) to produce silver chloride ($$AgCl$$) and sodium nitrate ($$NaNO_3$$). The law which satisfies this equation is ___________________ .

A
conservation of mass

B
conservation of energy

C
newton's law

D
dalton's law

Solution

Reaction:

$$NaCl+AgNO_3 \rightarrow AgCl+NaNO_3$$

Mol : 1 mol 1 mol 1 mol 1 mol
Mass : 58.5 g 170 g 143.5 g 85 g

Total mass of reactants is equal to the total mass of products. This is the law of conservation of mass.
Question 8
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A monoatomic element is:

A
nitrogen

B
hydrogen

C
radon

D
oxygen

Solution

Monoatomic elements are elements that are stable as single atoms. The chemical elements which are stable single-atom molecules at standard temperature and pressure (STP) are noble gases. These are helium, neon, argon, krypton, xenon, and radon.
Question 9
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Two chemical species $$X$$ and $$Y$$ combine together to form a product $$P$$ which contains both $$X$$ and $$Y$$

$$X + Y \rightarrow P$$

$$X$$ and $$Y$$ cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species $$X, Y$$ and $$P$$ are correct?

(i) $$P$$ is a compound
(ii) $$X$$ and $$Y$$ are compounds
(iii) $$X$$ and $$Y$$ are elements
(iv) $$P$$ has a fixed composition

A
(i), (ii) and (iii)

B
(i), (ii) and (iv)

C
(ii), (iii) and (iv)

D
(i), (iii) and (iv)

Solution

X and Y are elements as they can not be broken down into simpler substances. They combine in fixed proportion to give compound P.

Hence it is (i), (iii) and (iv).
Question 10
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Consider the following statements:
(a) Molecular mass of $$CH_3OH$$ is $$32\ u.$$
(b) In $$NH_3$$, the ratio of $$N$$ and $$H$$ by mass is $$14: 3.$$
(c) The formula mass of $$CaCl_2$$ is $$ 111\ u.$$
(d) Isotopes have same mass number.

Which of the above statements are correct?

A
$$\text {(a) and (c)}$$

B
$$\text {(a), (b) and (d)}$$

C
$$\text {(a), (b) and (c)}$$

D
$$\text {(a), (c) and (d)}$$

Solution

a) Molecular mass of $$CH_3OH = 12 + 4 \times 1 + 16 = 32\ u$$. This is correct statement.

b) In $$NH_3$$, the ratio of $$N$$ and $$H$$ by mass is $$14:3.$$, This is correct statement.

c) Formula mass of $$CaCl_2 = 40 + 2 \times 35.5 = 111\ u$$. This is correct statement.

d) Isotopes have the same atomic number but different mass numbers. For example $$^{12}_6C$$ and $$^{14}_6C.$$ Hence given statement is incorrect.

Hence, option $$C$$ is correct.

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Atoms and Molecules Test - 32

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Atoms and Molecules Test - 32

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Question 1

brass

graphite

silicon

nitrogen

Solution

Question 2

$$0.75$$$$N_A$$

$$1.5$$$$N_A$$

$$21$$$$N_A$$

$$14$$$$N_A$$

Solution

Question 3

18g of water is formed by the combination of 16g oxygen with 2g of hydrogen.

18g of water in liquid state is obtained by heating 18g of ice.

18g of water is completely converted into vapour state on heating.

18g of water freezes at $$4^{o}C$$ to give same mass of ice.

Solution

Question 4

233.5 gm/mole

249.5 gm/mole

251.5 gm/mole

247.5 gm/mole

Solution

Question 5

$$CO_2$$

$$CO$$

Both $$CO_2$$ and $$CO$$ have same mass

None of the above

Solution

Question 6

96 gm/mole

98 gm/mole

94 gm/mole

80 gm/mole

Solution

Question 7

conservation of mass

conservation of energy

newton's law

dalton's law

Solution

Question 8

nitrogen

hydrogen

radon

oxygen

Solution

Question 9

(i), (ii) and (iii)

(i), (ii) and (iv)

(ii), (iii) and (iv)

(i), (iii) and (iv)

Solution

Question 10

$$\text {(a) and (c)}$$

$$\text {(a), (b) and (d)}$$

$$\text {(a), (b) and (c)}$$

$$\text {(a), (c) and (d)}$$

Solution

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