Tag: avogadro law

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Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. $6.023 \times 10^{23}$
  2. $3.45 \times 10^{25}$
  3. $55.4 \times 10^{23}$
  4. $18 \times 10^{23}$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $\text{B}$.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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 $6.02 \times 10^{23}$

  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.
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Avogadro's number is NOT equal to:

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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)
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Number of molecules in one litre of water is :

  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. $55.5 \times 6.023 \times 10^{23}$
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro 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) 

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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}$.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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)

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
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