Atoms and Molecules Test

Result

Atoms and Molecules Test - 28

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
1 / -0

A sample of vitamic C is known to contain $$2.58 \times10^{24}$$ oxygen atoms. How many moles of oxygen atoms are present in the sample?

A
2.28 moles

B
2.14 moles

C
1 moles

D
4.28 moles

Solution

$$6.023 \times 10^{23}$$ atoms = $$1$$ mole of oxygen atoms

$$\therefore$$ Number of moles of oxygen atoms in $$2.58 \times 10^{24}$$ atoms $$= \dfrac {2.58 \times 10^{24}}{6.023\times 10^{23}} = 4.28\ mol$$

$$\therefore 4.28$$ moles of oxygen atoms are present in the sample.

Hence, the correct answer is option $$D$$.
Question 2
1 / -0

Which has more number of atoms: $$100$$ g of $$N_2$$ or $$100$$ g of $$NH_3$$?

A
$$NH_3$$

B
$$N_2$$

C
Both have same number of atoms

D
Cannot be determined

Solution

Atomic mass of N = 14 u
Atomic mass of H = 1 u

Number of moles = $$\dfrac {Mass}{Molar\ Mass}$$

$$(i) \ 100 g \ N_2$$ $$= \dfrac {100}{(14 \times 2)}$$ moles $$= \dfrac {100}{28}$$ moles

Number of $$N_2$$ molecules $$= \dfrac {100}{28} \times 6.022 \times 10^{23}$$

1 molecule of $$N_2$$ has 2 atoms. So, number of $$N$$ atoms $$= \dfrac {100}{28} \times 6.022 \times 10^{23}\times 2 = 43.01 \times 10^{23}$$ atoms

$$(ii) \ 100 g \ NH_3 = \dfrac {100}{14 + (3 \times 1)} = \dfrac {100}{17}$$ moles

$$= \dfrac {100}{17} \times 6.022 \times 10^{23}$$ molecules

$$= \dfrac {100}{17} \times 6.022 \times 10^{23} \times 4$$ atoms (since one molecule of $$NH_3$$ has 4 atoms.)

$$= 141.69 \times 10^{23}$$ atoms

$$\therefore$$ $$NH_3$$ would have more atoms
Question 3
1 / -0

Raunak took 5 moles of carbon atoms in a container and Krish also took 5 moles of sodium atoms in another container of same weight. Whose container has more number of atoms?

A
Raunak

B
Krish

C
Both have same

D
None of these

Solution

Equal moles of different atoms contain the same number of atoms.

1 mole has $$6.023\times 10^{23}$$ atoms.

Both have 5 moles of atoms.

Therefore, the number of atoms $$= 5\times 6.023\times 10^{23}$$.

Hence the correct option is C.
Question 4
1 / -0

The visible universe is estimated to contain $$10^{22}$$ stars. How many moles of stars are present in the visible universe?

A
$$6.023 \times 10^{23}$$ moles

B
$$6.023$$ moles

C
$$1.5$$ moles

D
$$0.0166$$ moles

Solution

1 mole of stars equals $$6.023 \times 10^{23}$$ stars
$$\therefore $$ Number of moles of stars $$= \dfrac{10^{22}}{N_A}$$ $$=\dfrac {10^{22}}{6.023 \times 10^{23}}$$$$= 0.0166$$ moles

Option $$D$$ is correct.
Question 5
1 / -0

Cations and anions present (if any) in $$NH_4NO_3$$ are :

A
Anions: $$NO_{3}^{2-}$$ Cations: $$NH_{4}^{3+}$$

B
Cations: $$NO_{3}^{-}$$ Anions: $$NH_{4}^{2+}$$

C
Cations: $$NO_{3}^{-}$$ Anions: $$NH_{4}^{+}$$

D
Anions: $$NO_{3}^{-}$$ Cations: $$NH_{4}^{+}$$

Solution

Ions present in $$NH_4NO_3$$ are:
Cations$$\rightarrow NH_4^+$$
Anions$$\rightarrow NO_3^-$$
Question 6
1 / -0

A sample of pure water, irrespective of source, contains 88.89% oxygen and 11.11% hydrogen
by mass. The data supports the:

A
law of conservation of mass

B
law of constant composition

C
law of multiple proportion

D
law of reciprocal proportion

Solution

According to the law of constant composition in a given compound, the elements always combine in the same proportion as each other.

Water($$H_{2}O$$) molecule consists of two hydrogen atoms of relative mass 1 and one oxygen atom of relative mass 16.

Therefore, the ratio in which 2 atoms of hydrogen and one atom of oxygen are combined is $$1:8$$ and will always be the same irrespective of the source of water.

Therefore, the correct option is $$B$$
Question 7
1 / -0

The formula and molecular mass of common salt is :

A
$$NaCl, 58.5$$

B
$$MgCl_2, 46$$

C
$$CaCl_2, 62$$

D
$$FeCl_3, 54$$

Solution

Molecular formula of common salt (sodium chloride) is$$ NaCl.$$ Its molar mass is $$23 + 35.5 = 58.5 g mol^{-1}$$
Question 8
1 / -0

$$10.0\ g$$ of $$CaCO_{3}$$ on heating gave $$4.4\ g$$ of $$CO_{2}$$ and $$5.6\ g$$ of $$CaO$$. This observation is in agreement with the:

A
law of constant composition

B
law of multiple proportion

C
law of reciprocal proportion

D
law of conservation of mass

Solution

$$CaCO_{3}\rightarrow CaO + CO_{2}$$
10 gm 5.6 gm 4.4 gm

Mass of $$CaCO_{3}\: (10\ gm) =$$ Mass of $$CaO\ (5.6\ gm)$$ + Mass of $$CO_{2}\ (4.4\ gm)$$

Hence, it proves the law of conservation of mass.
Question 9
1 / -0

Combined atoms have more:

A
unstability

B
stability

C
attraction

D
name of these

Solution

It has been observed that a system that has minimum energy is stable. The theory of chemical bonding shows that the formation of the chemical bonds decreases the potential energy of the system. Hence, two atoms combine to attain a state of lower potential energy and thus acquire more stability.
Example: Sodium electronic configuration
$$Na\longrightarrow 1s^22s^22p^63s^1$$ or $$2,8,1$$
$$(Z=11)$$
Chlorine electronic configuration
$$Cl\longrightarrow 1 s^2 2s^2 2p^6 3s^2 3p^5$$ or $$2,8,7$$
$$(Z=17)$$

$$\underset {2,8,1}{Na}+\underset {2,8,7}{Cl}\longrightarrow \underset {2,8}{Na^+}+\underset {2,8,8}{Cl^-}$$

Sodium is less stable with $$2,8,1$$ electronic configuration and more stable with $$2,8$$ electronic configuration. Similarly, chlorine is more stable with $$2,8,8$$ configuration, because both have a complete octet.
$$Na^++Cl^-\longrightarrow Na^+Cl^-$$ Atoms combined by an ionic bond. Both are more stable in a combined state.
Question 10
1 / -0

The formula and molecular mass of ethanol is:

A
$$C_3H_6O = 34 g mol^{-1}$$

B
$$C_2H_6O_2 = 62 g mol^{-1}$$

C
$$C_2H_5O = 45 g mol^{-1}$$

D
$$C_2H_6O = 46 g mol^{-1}$$

Solution

Molecular formula of ethanol is $$C_2H_5OH $$.

Molar mass of $$= C_2H_6O = 2 \times 12 + (6 \times 1) + 16 = 46 g mol^{-1}$$

User

Question Analysis

Correct -
Wrong -
Skipped -

My Perfomance

Score
-
out of -
Rank
-
out of -

Re-Attempt Weekly Quiz Competition

Atoms and Molecules Test - 28

Result

Atoms and Molecules Test - 28

Score

-

Rank

-

SHARING IS CARING

Question 1

2.28 moles

2.14 moles

1 moles

4.28 moles

Solution

Question 2

$$NH_3$$

$$N_2$$

Both have same number of atoms

Cannot be determined

Solution

Question 3

Raunak

Krish

Both have same

None of these

Solution

Question 4

$$6.023 \times 10^{23}$$ moles

$$6.023$$ moles

$$1.5$$ moles

$$0.0166$$ moles

Solution

Question 5

Anions: $$NO_{3}^{2-}$$ Cations: $$NH_{4}^{3+}$$

Cations: $$NO_{3}^{-}$$ Anions: $$NH_{4}^{2+}$$

Cations: $$NO_{3}^{-}$$ Anions: $$NH_{4}^{+}$$

Anions: $$NO_{3}^{-}$$ Cations: $$NH_{4}^{+}$$

Solution

Question 6

law of conservation of mass

law of constant composition

law of multiple proportion

law of reciprocal proportion

Solution

Question 7

$$NaCl, 58.5$$

$$MgCl_2, 46$$

$$CaCl_2, 62$$

$$FeCl_3, 54$$

Solution

Question 8

law of constant composition

law of multiple proportion

law of reciprocal proportion

law of conservation of mass

Solution

Question 9

unstability

stability

attraction

name of these

Solution

Question 10

$$C_3H_6O = 34 g mol^{-1}$$

$$C_2H_6O_2 = 62 g mol^{-1}$$

$$C_2H_5O = 45 g mol^{-1}$$

$$C_2H_6O = 46 g mol^{-1}$$

Solution

User

Question Analysis

My Perfomance

Score

-

Rank

-

Results Announcement on: coming Monday

Stay Tuned: We’ll update you on your result via email or SMS.