Tag: quantitative chemistry

Quizzes (10) Questions (111)

Questions Related to quantitative chemistry

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

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]

  1. $\cfrac {25} {\pi N}$
  2. $\cfrac {100} {\pi N}$
  3. $\cfrac {6} {\pi N}$
  4. $\cfrac {25} {4N\pi}$
Reveal answer Fill a bubble to check yourself
B Correct answer
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}$
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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

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

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

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

  1. van't Haff - avogadro's law

  2. van't Hoff Boyle's law

  3. van't Hoff's law

  4. Henry's law
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

van't Hoff's law for osmotic pressure states that for solutions at the same temperature and pressure, the molar concentrations (and thus the number of particles n) are equivalent.

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

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

  1. Dalton's theory

  2. Avogardro's hypothesis

  3. Berzelius hypothesis

  4. Law of gaseous volume
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  1. $2.1 N _ { A }$
  2. $3 N _ { A }$
  3. $6 N _ { A }$
  4. $ N _ { A }$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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:

  1. $1.66 \times 10^{-26}$
  2. $1.66 \times 10^{25}$
  3. $1.66 \times 10^{-24} x No$
  4. $6.024 \times 10^{25}$
Reveal answer Fill a bubble to check yourself
D Correct answer
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
$= 6.024 \times 10^{25} atom$

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

Which of the following represents the Avogadro number?

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Avogadro's number (6.022 x 10^23) represents the number of particles (atoms or molecules) in exactly one mole of a substance, regardless of the temperature or pressure.

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

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.

  1. N

  2. 2N

  3. N/2

  4. 4N
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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.

  1. x

  2. x/2

  3. x/4

  4. 2x
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

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

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?

  1. 2X

  2. X

  3. 0.5X

  4. 3X
Reveal answer Fill a bubble to check yourself
B Correct answer
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.