Tag: avogadro law

Questions Related to avogadro law

Calculate the number of iron atoms in a piece of iron weighing $2.8 g$. (Atomic mass of iron $=56$)

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $30.11\times { 10 }^{ 23 }$ atoms

  2. $3.11\times { 10 }^{ 23 }$ atoms

  3. $3.0115\times { 10 }^{ 22 }$ atoms

  4. $301.1\times { 10 }^{ 23 }$ atoms

Show answer
Correct Option: C
Explanation:
Given that, weight of iron =2.8 g
Atomic mass= 56
moles of iron$= \dfrac{\text{wt. of iron}}{\text{atomic mass}}=\dfrac{2.8}{56}=0.05\ moles$
1 mole $= 6.022 \times 10^{23}\ atoms$
0.05 moles $= 6.022 \times 0.05 \times 10^{23}\ atoms=3.0115 \times 10^{22}$ atoms
Option C is correct.

The value of the Avogadro constant is:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $6.022 \times 10^{13}$

  2. $6.022 \times 10^{22}$

  3. $6.022 \times 10^{23}$

  4. $6.022 \times 10^{24}$

Show answer
Correct Option: C
Explanation:

Avogadro constant $=6.022\times { 10 }^{ 23 }$


Avogadro constant is the number of constituent particles, usually atoms or molecules, that are contained in the amount of the substance given by one mole.

Therefore, the option is C.

What is the mass of $6.022\times { 10 }^{ 23 }$ molecules of ${NH} _{3}$?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $45.06g$

  2. $19.06\ g$

  3. $17.04g$

  4. $31.02g$

Show answer
Correct Option: C
Explanation:

$1\space mole$ of $NH _3$ has $6.023 \times 10^{23}$ molecules of $NH _3$.

So, the mass of $6.023 \times 10^{23}$ molecules of $NH _3$. is the mass of $1\space mole$ of $NH _3$  i.e. molar mass of $NH _3.$ 
Molar mass $= 14.01 + 3(1.01) = 17.04 \space g$

What would be the approximate weight of $1.204\times 10^{24}$ bromine atoms?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. 80 grams

  2. 120 grams

  3. 160 grams

  4. 180 grams

  5. 200 grams

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Correct Option: C
Explanation:

The atomic weight of bromine is 80.

So, 80-gram bromine contains Na atoms.
So, $1.204\times10^{24}$ bromine atoms will weigh:  $80\div 6.02\times10^{23}\times 1.204\times10^{24}=160\ gram$

How many molecules of water are present in a $0.25\ mole$ of $H _2O$?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $6.0\times{10}^{22}$

  2. $4.5\times 10^{23}$

  3. $1.5\times{10}^{23}$

  4. $18\times 10^{23}$

Show answer
Correct Option: C
Explanation:

$1\space mole$ of a compound has $6.023\times 10^{23}$ molecules in it.

$\Rightarrow 1\space mole =$$6.023\times 10^{23}$ molecules
$ 0.25\space mole = x$ molecules
$\Rightarrow x = (\dfrac{6.023}{4}) \times 10^{23}$$= 1.5\times 10^{23}$ molecules of water.

How many atoms of hydrogen are present in $7.8\ g$ of $Al{(OH)} _{3}$?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $6.0\times {10}^{22}$

  2. $1.8\times {10}^{23}$

  3. $1.7\times {10}^{23}$

  4. $5.1\times {10}^{22}$

Show answer
Correct Option: A
Explanation:

Molar mass of $Al(OH) _3 = 27 + 3\times 16 + 3\times 1 = 78\space g$

So, no. of moles of $Al(OH) _3 = \dfrac{7.8}{78} = 0.1\space moles$
$1\space mole$ of $Al(OH) _3$ has $6.023 \times 10^{23}$ atoms.
So, $0.1\space moles$ has $6.023 \times 10^{22}$ atoms.

$2K(s)+2{H} _{2}O(l)\rightarrow 2KOH(aq)+{H} _{2}(g)$
If $3.0$ moles of potassium react with excess water, what volume of hydrogen gas will be produced?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $1.5L$

  2. $22.4L$

  3. $67.2L$

  4. $33.6L$

Show answer
Correct Option: D
Explanation:

Given, $2K(s) + 2H _2O(l) \rightarrow 2KOH(aq) + H _2 (g)$

$2\space moles$ of Potassium on reaction gives $1 \space mole$ of Hydrogen [ 22.4 at STP]
$2\space moles$ of $K \rightarrow 22.4 \space Litres $ of $H _2$
$2\space moles$ of $K = \dfrac{3\times 22.4}{2} = 33.6 \space Litres$ of $H _2$
So, $33.6\space Litres$ of Hydrogen are produced.

Hydrogen, oxygen and carbon dioxide are taken in containers of $2 l$ volume each. Compare the ratio of the number of molecules of the three gases respectively, under same conditions of temperature and pressure.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. 1:8:22

  2. 1:1:1

  3. 1:16:44

  4. 1:8:44

Show answer
Correct Option: B
Explanation:

Using ideal gas law: PV =nRT

n = $\dfrac{V}{RT}$
here P, R and T= Constant, V = 2l
hence number of moles also equal  
the ration of moles equal to 1:1:1
 answer is B

What is the mass of $6.022\times { 10 }^{ 23 }$ formula units of ${({NH} _{4})} _{2}{SO} _{4}$?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $234.11\ g$

  2. $132.11\ g$

  3. $210.29\ g$

  4. $342.14\ g$

Show answer
Correct Option: B
Explanation:

$1\space mole$ of $(NH _4) _2SO _4$ has $6.023 \times 10^{23}$ formula units.

So, the mass of $6.023 \times 10^{23}$ formula units of $(NH _4) _2SO _4$. is molar mass of $(NH _4) _2SO _4$

Molar mass of $(NH _4) _2SO _4$ $= 2(14 + 4) + 32 + 4\times 16 = 132 \space g$

A mixture of helium and argon contains 3 moles of $He$ for every 2 moles of $Ar$. The partial pressure of argon in the mixture is

chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

  1. two thirds the total pressure

  2. one third the total pressure

  3. three fifths the total pressure

  4. two fifths the total pressure

Show answer
Correct Option: D
Explanation:

The partial pressure of any gas is the product of mole fraction and total pressure


$P _{Ar}=\dfrac{2}{2+3}.P _{total}$