Tag: avogadro's law

Questions Related to avogadro's law

State True or False.
Equal volumes of different gases under similar conditions of temperature and pressure contain equal number of atoms.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. True

  2. False

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Correct Option: B
Explanation:

The statement, "Equal volumes of different gases under similar conditions of temperature and pressure contain equal number of atoms." is false. The true statement is "Equal volumes of different gases under similar conditions of temperature and pressure contain equal number of moles."  For example, at STP conditions, 22.4 L of any gas corresponds to 1 mole.

Number of water molecules in one litre of pure water is :

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $6.023 \times 10^{23}$

  2. $3.45 \times 10^{25}$

  3. $55.4 \times 10^{23}$

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

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Correct Option: B
Explanation:

One mole of water has a mass of $18$ grams and a volume of $18$ mL (as the density of water is 1 g per cm$^3$).


Therefore, number of moles of water in $1$ litre $= \dfrac{1\times 1000}{18}$.

Number of molecules $= $ Number of moles $\times N _A$

                                          $= \dfrac{1\times 1000}{18} \times 6.023\times 10^{23}$

                                         $= 3.45\times 10^{25}$ molecules.

Hence, the correct answer is option $\text{B}$.

Statement 1: The number of gram molecules of oxygen in $6.02 \times 10^{24}\ CO$ molecules is 5.0.
Statement 2: The value of Avogadro number is $6.02 \times 10^{23}$

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Statement 1 is True, statement 2 is True, Statement 2 is a correct explanation of statement 1.

  2. Statement 1 is True, statement 2 is True, Statement 2 is not a correct explanation of statement 1.

  3. Statement 1 is True, Statement 2 is False.

  4. Statement 1 is False, Statement 2 is True.

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Correct Option: B
Explanation:

$6.02\times 10^{24}$ molecules of $CO=6.02\times 10^{23}\times 10$ i.e.., 10 moles of CO.
10 moles of CO contains 10 gm atoms of oxygen i.e.  5 gm molecules of oxygen.
hence the correct answer is A the given assertion is correct and reason is the correct explanation to the assertion.

Avogadro's number is NOT equal to:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. the number of atoms in 11.2 L of $\displaystyle { O } _{ 2 }$ at STP

  2. the number of atoms in 1 mole of $\displaystyle He$ at STP

  3. the number of electrons in 96,500 coulombs

  4. the number of $\displaystyle { SO } _{ 4 }^{ 2- }$ ions in 1 L of 0.5 M sulphuric acid

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Correct Option: D
Explanation:
$Avogadro's \ Number= N _A= 6.02 \times 10^{23}$
$1$ mole of any substance has $N _A$ number of atoms, molecules or ions etc. 
Therefore, moles of $SO _4^{2-}$ ions in $1 \ L$ of $0.5 \ M \ H _2SO _4$ will be 
$Molarity= \cfrac {Number \ of \ moles}{Volume \ of \ solution \ (in \ L)}$
$0.5 = \cfrac {moles}1$
$Number \ of \ moles = 0.5$
Hence, because $1$ mole of a substance $= N _A$
$\therefore \ 0.5$ moles of $SO _4^{2-} \neq N _A $ (Avogadro Number)

Number of molecules in one litre of water is :

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $\displaystyle \frac {6.023}{23.4} \times 10^{23}$

  2. $18 \times 6.023 \times 10^{23}$

  3. $\displaystyle \frac {18}{22.4} \times 10^{23}$

  4. $55.5 \times 6.023 \times 10^{23}$

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Correct Option: D
Explanation:

Number of moles of water molecules in 1 litre of water = 55.5 moles

Hence, number of molecules of water = 55.5$\times$ Avogadro number
So, option D is correct.

64 g of sulphur dioxide occupies $22.4\ L$ volume at STP.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. True

  2. False

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Correct Option: A
Explanation:

Molecular mass of $SO _2$ is 64. 

So, 1 mole (64 grams) of sulphur dioxide will occupy $22.4\ L$ at STP. ( Avogadro's law)

Which of the following expressions is equal to the number of iron ($Fe$) atoms present in $10.0$ g $\displaystyle Fe$ ? (atomic mass of $\displaystyle Fe$ = $55.9$ amu) 

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $ 10\times 55.9\times( 6.022\times { 10 }^{ 23 }) $ atoms

  2. $\dfrac{( 6.022\times { 10 }^{ 23 })}{10}\times 55.9$ atoms

  3. $ 10\times \dfrac {( 6.022\times { 10 }^{ 23 } )}{ 55.9}$ atoms

  4. $\dfrac {55.9}{10} \times ( 6.022\times { 10 }^{ 23 } ) $

  5. $ \dfrac {10}{ ( 55.9\times 6.022\times { 10 }^{ 23 } )} $ atoms

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Correct Option: C
Explanation:

The expression $\displaystyle 10\times \left( 6.022\times { 10 }^{ 23 } \right)/ 55.9$ is equal to the number of iron (Fe) atoms present in 10.0 g Fe.
The atomic mass of Fe is 55.9 g/mol.
The mass of Fe is 10.0 g. Mass is divided with atomic mass to obtain number of moles.
The number of moles of Fe $ =  \dfrac {10.0}{55.9}$ moles.
The number of moles is multiplied with avogadro's number to obtain the number of Fe atoms.
The number of Fe atoms  $ =  \dfrac {10.0}{55.9} \times 6.023 \times 10^{23}$.

14 g of nitrogen contains $3.01 \times 10^{23}$ nitrogen molecules.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. True

  2. False

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Correct Option: A
Explanation:

1 mole nitrogen contains $6.02\times10^{23}$ nitrogen molecules.

Thus 14 gram nitrogen will contain $14/28.Na=0.5Na=3.01\times10^{23}$ nitrogen molecules. ( Molecular weight of nitrogen is 28)

Mass of $12.044 \times 10^{23}$ atoms of hydrogen is:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $1 g$

  2. $2 g$

  3. $3 g$

  4. $4 g$

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Correct Option: B
Explanation:
$\dfrac{mass}{molecular\, weight}=\dfrac{No.\, of\, atoms}{N _{A}}$
$mass=\dfrac{12.044\times 10^{23}}{6.022\times 10^{23}}\times 1$ {Hydrogen molecular weight =$ 1 g/mol$}
$Mass = 2g$

1 g of $^{12}C$ contains $6.022 \times 10^{23}$ atoms of the isotope.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Because according to Avegadro's law,

$1$ mole of $C$ contains $6.022\times { 10 }^{ 23 }$ atoms and $1$ mole of $C$ weighs $12gm$
$\therefore$  $12g$ of $C$ weighs $6.022\times { 10 }^{ 23 }$ atoms