Tag: avogadro law

Questions Related to avogadro law

Ethane burning in oxygen to give carbon dioxide and steam. The volume ratio of reactants to products is ______________.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. 2 : 6 : 4 : 3

  2. 2 : 7 : 2 : 5

  3. 3 : 4 : 4 : 6

  4. 2 : 7 : 4 : 6

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Correct Option: D
Explanation:

The equation for the combustion reaction of ethane can be written as :
$2C _{2}H _{6} + 7O _{2} \rightarrow 4CO _{2} + 6H _{2}O$
Therefore the volume ratio of reactants and products $= 2 : 7 : 4 : 6$

The number of atoms in 67.2 L of ${ NH } _{ 3 }$(g) at STP is:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. 9 ${N } _{ A }$

  2. 12 ${N } _{ A }$

  3. 3 ${N } _{ A }$

  4. 4 ${N } _{ A }$

Show answer
Correct Option: B
Explanation:
By Avogadro law,
 22.4 liter of any gas at STP$ = $1mole
                $ =6.022\times { 1 }0^{ 23 }$ molecules of gas
                $ =$NA (Avogadro number)

So, in 67.2 L of ${ NH } _{ 3 }=?$
    22.4 L of $ { NH } _{ 3 }=N _A$
     1 L of ${ NH } _{ 3 }=\cfrac { NA }{ 22.4 } $

67.2 L of $ { NH } _{ 3 }=\cfrac { 67.2 }{ 22.4 } \times NA$
                          $ =3N _A$ molecules

Now, each molecule contain 4 atoma
Number of atoms $= 4\times 3N _A = 12N _A$ atoms

Four one litre flasks are separately filled with gases $O _2, F _2, CH _4$ and $CO _2$ under same conditions. 


The ratio of the number of molecules in these gases are:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $2 : 2 : 4 : 3$

  2. $1 : 1 : 1 : 1$

  3. $1 : 2 : 3 : 4$

  4. $2 : 2 : 3 : 4$

Show answer
Correct Option: B
Explanation:
Avogadro's law: It states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

$\\ n _{1} : n _{2} : n _{3} : n _{4} = \cfrac{PV}{RT} : \cfrac{PV}{RT} : \cfrac{PV}{RT} : \cfrac{PV}{RT} = 1 : 1 : 1 : 1 $

So, the ratio of no. of molecules $= 1: 1: 1: 1$

The correct option is $B.$

A sample of municipal water contains one part of urea (molecular wt $=60$) per million parts of water by weight. The number of urea molecules in a drop of water of volume $0.05\ ml$ is 

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $2.5\times 10^{14}$

  2. $5\times 10^{14}$

  3. $5\times 10^{13}$

  4. $5\times 10^{15}$

Show answer
Correct Option: B
Explanation:

$1 \ ppm = 1 \ mg/L = 10^{-3} g/L$

Water sample contains $1 \ ppm$ urea concentration.

$\therefore \ 10^{-3} \ g$ of urea in $ 1 \ L$

$x \ g$ urea in $0.05 \times 10^{-3} \ L$

$x= 0.05 \times 10^{-6} \ g$

$60 \ g$ urea $=6.023 \times 10^{23} \ molecules$

$0.05 \times 10^{-6} \ g = n \ molecules$

$n = \cfrac {6.023 \times 10^{23} \times 0.05 \times 10^{-6}}{60}$

$=0.005 \times 10^{17}$

$=5 \times 10^{14} \ molecules$

According to Avogadro's law the volume of a gas will ____ as _____ if ____ are held constant.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. increases, number of moles; P & T

  2. decreases, number of moles; P & T

  3. increases; T & P; number of moles

  4. decreases; P & T; number of moles

Show answer
Correct Option: A
Explanation:

According to Avogadro's law: Equal volume of all gases at same temperature and pressure will have same no. of molecules.

OR
For a given mass of ideal gas,
Volume$\propto$Number of moles of the gas (if temperature and pressure are constant) 
So, volume of the gas will increase as the number of moles if pressure (P) and temperature (T) are held constant.

What is the value of $n$ in the following equation?


$Cr\left( OH \right) _{ 4 }^{ - }+OH^{ - }\longrightarrow  Cr{ O } _{ 4 }^{ 2- }+H _{ 2 }O\ +\ ne^-$

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $3$

  2. $6$

  3. $5$

  4. $2$

Show answer
Correct Option: B

The critical density of the gas $CO _2$ is 0.44 $g\ cm^{–3}$ at a certain temperature. If $r$ is the radius of the molecule, $r^3$ in $cm^3$ is approximate: 


[N is Avogadro number]

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $\cfrac {25} {\pi N}$

  2. $\cfrac {100} {\pi N}$

  3. $\cfrac {6} {\pi N}$

  4. $\cfrac {25} {4N\pi}$

Show answer
Correct Option: B
Explanation:
Critical density of a gas $= 0.44 gcm^{-3}$
Molar mass of $CO _2$ = 44 g/mole

$Density = mass /volume $
Mass of N molecules = 44 g of $CO _2$    $N =6.022\times 10^{23}$

Mass of 1 molecule $= \dfrac{44}{N}$
The volume of 1 molecule $=\cfrac {4}{3}\pi r^3$
Putting the values,
$ 0.44 = \dfrac{\dfrac{44}{N}}{\cfrac {4}{3}\pi r^3}$

$ r^3 = \dfrac{100}{\pi N}$

Which facts are revealed from Avogadro's law for ideal gases?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. The distance between molecules is much large than the actual dimension of molecules.

  2. Equal number of molecules of different gases under identical conditions of temperatures and pressure occupy the same volume.

  3. Saturated vapours obey gas laws

  4. 1 mole of a gas contains $6.023\times 10^{23}$ molecules of gases.

Show answer
Correct Option: B,D
Explanation:

Avogadro's Law :
It states "equal volumes of any two gases at the same temperature and pressure contain the same number of molecules".

$V  \propto  n$ (At constant P and T)

$\dfrac{V _1}{V _2} = \dfrac{n _1}{n _2}$

and each gas's one mole contains $6.023\times 10^{23}$ molecules.

The law which suggests $n _1 = n _2$ for two solutions at same temperature and pressure is 

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. van't Haff - avogadro's law

  2. van't Hoff Boyle's law

  3. van't Hoff's law

  4. Henry's law

Show answer
Correct Option: C

One gram molecule of any gas at $NTP$ occupies $22.4\ L$. This fact was derived from:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Dalton's theory

  2. Avogardro's hypothesis

  3. Berzelius hypothesis

  4. Law of gaseous volume

Show answer
Correct Option: B
Explanation:

According to Avogadro's law, 1 mole of every gas occupies 22.4L at $NTP$.

From ideal gas equation,
$PV=nRT$. . . . . . .(1)
At $NTP$,
$T=273K$
$P=1atm$
$n=1$
$R=0.0821atm L/K mol$
from equation (1),
$V=\dfrac{nRT}{P}$
$V=\dfrac{1\times 0.0821\times 273}{1}=22.4L$
The correct option is B.