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

What is the mass of $6.022\times { 10 }^{ 23 }$ formula units of ${({NH} _{4})} _{2}{SO} _{4}$?

  1. $234.11\ g$
  2. $132.11\ g$
  3. $210.29\ g$
  4. $342.14\ g$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$1\space mole$ of $(NH _4) _2SO _4$ has $6.023 \times 10^{23}$ formula units.

So, the mass of $6.023 \times 10^{23}$ formula units of $(NH _4) _2SO _4$. is molar mass of $(NH _4) _2SO _4$

Molar mass of $(NH _4) _2SO _4$ $= 2(14 + 4) + 32 + 4\times 16 = 132 \space g$

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

A mixture of helium and argon contains 3 moles of $He$ for every 2 moles of $Ar$. The partial pressure of argon in the mixture is

  1. two thirds the total pressure

  2. one third the total pressure

  3. three fifths the total pressure

  4. two fifths the total pressure
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The partial pressure of any gas is the product of mole fraction and total pressure


$P _{Ar}=\dfrac{2}{2+3}.P _{total}$

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

What could be better than a dozen $(12)$ donuts? How about a baker's dozen $(13)$ of donuts? Another large unit of measurement is known as Avogadro's number $(6.022\times 10^{23})$.
What is TRUE about Avogadro's number?

  1. Avogadro's number is the number of particles in one mole of any element.
  2. The molar mass of a substance will contain $6.022\times 10^{23}$ molecules.
  3. There are $6.022\times 10^{23}g$ of carbon in $12$ mol of $C - 12$.
  4. $6.022\times 10^{23}$ atoms of any element will have the exact same mass regardless of the identity of the element.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Avagadro constant i.e. $6.023 \times 10^{23}$ particles is the number of constituent particles, usually atoms or molecules, that are contained in the amount of substance given by $1\space mole$. 

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

In the ideal gas equation, the unit of universal gas constant R is?

  1. Mole-atm/K

  2. Litre/mole

  3. Litre-atm/mole.K

  4. erg/K
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In ideal gas equation,


$R=\dfrac{PV}{nT}$ where, 
$P$ is the pressure in 'Atmosphere (atm)'
$V$ is the volume in Litre
$n$ is the number of moles
$T$ is the Temperature in Kelvin (K) 

$ \therefore $Units of $R$= litre.atm/mol.K

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

A sample of gas has a volume of 0.2 litres measured at 1 atm pressure and $0^oC$. At the same pressure, at $273^oC$, its volume will become:

  1. 0.1 litre

  2. 0.4 litre

  3. 0.8 litre

  4. 0.6 litre
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Charles's law


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

$\dfrac{0.2}{273}=\dfrac{V}{546}$

$V=0.4\ litres$

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

A gas is initially at $1$ atm pressure. To compress it to $1/4$ th of its initial volume, pressure to be applied is:

  1. $1$ atm
  2. $2$ atm
  3. $4$ atm
  4. $1/4$ atm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to boyle's law,


$P _1V _1=P _2V _2$

$\Rightarrow 1.V=\frac{V}{4}.P _2$

$\Rightarrow P _2=4\ atm$

Hence, the correct option is $C$