Atoms and Molecules Test

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Atoms and Molecules Test - 55

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following correctly represents Dalton's symbols?

A
1 : Oxygen, 2 : Hydrogen, 3: Nitrogen, 4: Carbon and 5: Sulphur

B
1 : Hydrogen, 2 : Nitrogen, 3: Oxygen, 4: Carbon and 5: Sulphur

C
1 : Hydrogen, 2 : Nitrogen, 3: Oxygen, 4: Sulphur and 5: Carbon

D
1 : Hydrogen, 2 : Carbon, 3: Oxygen, 4: Sulphur and 5: Nitrogen

Solution

The following correctly represents Dalton's symbols.
1: oxygen, 2: hydrogen, 3: nitrogen, 4: carbon, and 5: sulphur
Hence, option $$A$$ is correct.
Question 2
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What is the formula mass unit of $$HCl$$ ?

A
$$36.5$$

B
$$35.5$$

C
$$32.5$$

D
$$34.5$$

Solution

Formula mass unit of $$HCl$$ is : Mass of hydrogen $$(1) +$$ mass of chlorine$$ (35.5) = (35.5+1) = 36.5$$
Hence, option A is correct.
Question 3
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What is the formula unit mass of sodium chloride?

A
58.5

B
35.5

C
23

D
40

Solution

The formula of sodium chloride is $$NaCl$$
Atomic weight of sodium $$(Na)$$ is $$23\ g/mol$$
Atomic weight of chloride $$(Cl)$$ is $$35.45\ g/mol$$
Therefore, the formula unit mass of sodium chloride $$ (NaCl)$$ is $$23+35.45 = 58.45\ g/mol$$ which nearly equals to $$58.5\ g/mol$$
Hence, option $$A$$ is correct.
Question 4
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An ion is produced as a result of gain or loss of electrons by an atom. In $$Au^{3+}$$ ion, 3 electrons are ___________by $$Au$$ atom.

A
gained

B
lost

C
shared

D
None of the above

Solution

$$Au$$ looses 3 electrons to form the cation $$Au^{3+}$$.
Question 5
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When the size of a spherical nanoparticle decreases from $$\text {30 nm}$$ to $$\text {10 nm}$$. The ratio surface area/volume becomes:

A
$$1/3$$ of the original

B
$$3$$ times the original

C
$$1/9$$ of the original

D
$$9$$ times the original

Solution

From the given information.
$$\dfrac{\left(surface\ area\right)}{volume}=\dfrac{\left(\pi d^{2}\right)}{\left(\dfrac{\pi d^{2}}{6}\right)}=\dfrac{6}{d}$$
$$d_{1}=\ 30nm\ ,\ d_{2}=10nm$$
$$\therefore$$ $$\dfrac{\left(\dfrac{surface\ area}{volume}\right)_{2}}{\left(\dfrac{surface\ area}{volume}\right)_{1}}=\dfrac{\left(\dfrac{6}{d_{2}}\right)}{\left(\dfrac{6}{d_{1}}\right)}\ =\ \dfrac{d_{1}}{d_{2}}$$ = $$\dfrac{30}{10}$$ = $$3$$

Hence, the correct answer is option $$B$$.
Question 6
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Select the smallest atom.

A
$$F$$

B
$$Cl$$

C
$$Br$$

D
$$I$$

Solution

In a group, on moving down the group, the atomic radius increases as electrons are added to the new shell.

Hence, the smallest atom is $$\displaystyle F$$.
Question 7
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Which one of the following atoms will have largest size?

A
Ca

B
Na

C
Mg

D
Be

Solution

Atomic size increased down the group and decreases in the period from left to right. If we look at the position of $$Be, Mg$$, and $$Ca$$ then it is observed that they are present in the same column which indicates $$Ca$$ has a larger size than $$Be$$ and $$Mg. \ Ca$$ is also larger in size compared to $$Na$$ because it has a higher number of electrons that are present farther from the nucleus.
So, calcium ($$Ca$$) is the largest size among given atoms.

Hence, the correct option is $$\text{A}$$.
Question 8
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One sample of air is found to have 0.03% and another sample has 0.02% carbon dioxide. This illustrates that:

A
air is a compound

B
air is an element

C
air does not follow the law of constant proportions

D
air is a mixture

Solution

Yes, this illustrates that air is a mixture because air is a composition of many types of gas.
A mixture contains a combination of several elements or compounds. For a mixture, the ratio of constituent elements or compounds is not fixed and it can vary.
Therefore, option D is the correct answer.
Question 9
1 / -0

$$SO_2$$ gas was prepared by
(i) burning sulphur in oxygen,
(ii) reacting sodium sulphite with dilute $$H_2SO_4$$ and
(iii) heating copper with $$conc. H_2SO_4$$. It was found that in each case sulphur and oxygen combined in the ratio of 1 : 1. The data illustrates the law of :

A
conservation of mass

B
multiple proportions

C
constant proportions

D
reciprocal proportions

Solution

Ratio of sulfur & oxygen $$=1:1.$$
Thus illustrates law of constant proportions because the ratio is a constant.
Question 10
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$$1$$ mole of a compound contains $$1$$ mole of $$C$$ and $$2$$ moles of $$O$$. The molecular weight of the compound is :

A
3

B
12

C
32

D
44

Solution

Given that :

1 mole of compound contains 1 mole of $$C$$ and 2 moles of $$O$$.

Therefore, the molecular formula of the compound is $$C_{1}O_{2}$$.

$$\Rightarrow$$ Molecular Formula of the compound $$ = CO_{2}$$

Molecular weight of the compound = $$1 \times 12 $$(Molecular weight of the carbon) $$ + 2\times 16 $$ (Molecular weight )of the oxygen)
$$ = 12 + 32 = 44 $$

Molecular weight of the compound $$= 44g$$

$$\therefore $$ Molecular weight of 1 mole of the compound $$= 44g$$

Hence the correct option is D.

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Atoms and Molecules Test - 55

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Atoms and Molecules Test - 55

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Question 1

1 : Oxygen, 2 : Hydrogen, 3: Nitrogen, 4: Carbon and 5: Sulphur

1 : Hydrogen, 2 : Nitrogen, 3: Oxygen, 4: Carbon and 5: Sulphur

1 : Hydrogen, 2 : Nitrogen, 3: Oxygen, 4: Sulphur and 5: Carbon

1 : Hydrogen, 2 : Carbon, 3: Oxygen, 4: Sulphur and 5: Nitrogen

Solution

Question 2

$$36.5$$

$$35.5$$

$$32.5$$

$$34.5$$

Solution

Question 3

58.5

35.5

23

40

Solution

Question 4

gained

lost

shared

None of the above

Solution

Question 5

$$1/3$$ of the original

$$3$$ times the original

$$1/9$$ of the original

$$9$$ times the original

Solution

Question 6

$$F$$

$$Cl$$

$$Br$$

$$I$$

Solution

Question 7

Ca

Na

Mg

Be

Solution

Question 8

air is a compound

air is an element

air does not follow the law of constant proportions

air is a mixture

Solution

Question 9

conservation of mass

multiple proportions

constant proportions

reciprocal proportions

Solution

Question 10

3

12

32

44

Solution

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