Tag: quantitative chemistry

Questions Related to quantitative chemistry

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

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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.

If  $N _ { A }$ is Avogadro's number, then calculate the number of electrons in  $4.2\ g$  of  $N ^ { 3- }$.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $2.1 N _ { A }$

  2. $3 N _ { A }$

  3. $6 N _ { A }$

  4. $ N _ { A }$

Show answer
Correct Option: A
Explanation:
$N^{3-}$ contains 10 electrons.

Number of moles $= \dfrac {4.2}{14} $
                                     
                                       $=0.3\ moles$

No of electrons in $0.3\ moles = 0.3\times N _A\times 10$

                                        $=3\ N _A$

Hence, option B is correct.

Mass of the one atom of the element X is $1.66 \times 10^{-26}$ g. Number of atoms in 1 g of the element is:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $1.66 \times 10^{-26}$

  2. $1.66 \times 10^{25}$

  3. $1.66 \times 10^{-24} x No$

  4. $6.024 \times 10^{25}$

Show answer
Correct Option: D
Explanation:

Mass of one atom = $1.66 \times 10^{-26} g$
$1.66 \times 10^{-26} gm \rightarrow 1 \, atom$
$1 \, gm \rightarrow \dfrac{1}{1.66 \times 10^{-26}} $ atom
$= 6.024 \times 10^{25} atom$

Which of the following represents the Avogadro number?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Number of molecule present in 1 L of gas at N.T.P

  2. Number of molecule present in 22.4 L of gas at N.T.P

  3. Number of molecule present in 22.4 of gas at 298K and 1 atm pressure

  4. Number of molecule present in one mole of gas at any temp and pressure

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Correct Option: D

A vessel contains N molecules of oxygen at a certain temperature and pressure. How many molecules of sulphur dioxide can the vessel accommodate at the same temperature and pressure.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. N

  2. 2N

  3. N/2

  4. 4N

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Correct Option: A
Explanation:

As both have same volume and according to avagadro's law, equal volume of gases contains equal molecules so sulphur dioxide contains N molecules.

The gases chlorine, nitrogen, ammonia and sulphur dioxide are collected under the same conditions of temperature and pressure. If 20 litres of nitrogen contains 'x' no. of molecules, state the no. of molecules in 20 litres of ammonia.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. x

  2. x/2

  3. x/4

  4. 2x

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Correct Option: A
Explanation:

According to avagadro's law, equal volume of gases contains equal number of molecules. Therefore,  20 litres of ammonia will contain x number of molecule. 

A vessel contains X number of molecules of hydrogen gas at a certain temperature and pressure. Under the same conditions of temperature and pressure, how many molecules of nitrogen gas would be present in the same vessel?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. 2X

  2. X

  3. 0.5X

  4. 3X

Show answer
Correct Option: B
Explanation:

Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules" so same volume of nitrogen will have X number of molecules.