Tag: quantitative chemistry

Questions Related to quantitative chemistry

$2K(s)+2{H} _{2}O(l)\rightarrow 2KOH(aq)+{H} _{2}(g)$
If $3.0$ moles of potassium react with excess water, what volume of hydrogen gas will be produced?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $1.5L$

  2. $22.4L$

  3. $67.2L$

  4. $33.6L$

Show answer
Correct Option: D
Explanation:

Given, $2K(s) + 2H _2O(l) \rightarrow 2KOH(aq) + H _2 (g)$

$2\space moles$ of Potassium on reaction gives $1 \space mole$ of Hydrogen [ 22.4 at STP]
$2\space moles$ of $K \rightarrow 22.4 \space Litres $ of $H _2$
$2\space moles$ of $K = \dfrac{3\times 22.4}{2} = 33.6 \space Litres$ of $H _2$
So, $33.6\space Litres$ of Hydrogen are produced.

Hydrogen, oxygen and carbon dioxide are taken in containers of $2 l$ volume each. Compare the ratio of the number of molecules of the three gases respectively, under same conditions of temperature and pressure.

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. 1:8:22

  2. 1:1:1

  3. 1:16:44

  4. 1:8:44

Show answer
Correct Option: B
Explanation:

Using ideal gas law: PV =nRT

n = $\dfrac{V}{RT}$
here P, R and T= Constant, V = 2l
hence number of moles also equal  
the ration of moles equal to 1:1:1
 answer is B

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

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $234.11\ g$

  2. $132.11\ g$

  3. $210.29\ g$

  4. $342.14\ g$

Show answer
Correct Option: B
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 $(NH _4) _2SO _4$ $= 2(14 + 4) + 32 + 4\times 16 = 132 \space g$

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?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  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.

Show answer
Correct Option: A
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 $1\space mole$. 

One mole of any substance contains $6.022\times 10^{23}$ atoms/molecules. Number of molecules of $H 2SO _4$ present in $100$mL of $0.02$M $H _2SO _4$ solution is _________?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $12.044\times 10^{20}$ molecules

  2. $6.022\times 10^{23}$ molecules

  3. $1\times 10^{23}$ molecules

  4. $12.044\times 10^{23}$ molecules

Show answer
Correct Option: A
Explanation:

Moles of $H _2SO _4=$ Molarity of $H _2SO _4\times $ Volume of solution $(L)$


$=0.02\times 0.1$


$=2\times 10^{-3}$ moles

No. of $H _2SO _4$ molecules $=2\times 10^{-3}\times 6.022\times 10^{23}=12.044\times 10^{20}$ molecules


Therefore, the correct option is A.

Cations absorb $6.023\times 10^{22}$ electrons for their reduction. How many equivalents of the ion are reduced?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $0.1$

  2. $0.01$

  3. $0.001$

  4. $0.0001$

Show answer
Correct Option: A
Explanation:

1 equivalent of ion absorbs 6. 023 $\times 10^{23}$ electrons 

No. of equivalents reduced = $\dfrac{6.023\times 10^{22}}{6.023 \times  10^{23}}$= 0.1

The number of gram molecule of oxygen in $6.02 \times 10^{24}$ CO molecules is :

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. 10 gm molecules

  2. 5 gm molecules

  3. 1 gm molecules

  4. 0.5 gm molecules

Show answer
Correct Option: B
Explanation:

Given :


$6.02\times 10^{24}$ $CO$ molecules


We know,

$1$ mole $CO$ equivalent to $6.023\times 10^{23}$ molecules of $CO$

$6.023\times 10^{23}$ molecules of $CO$ contain $6.023\times 10^{23}$ atoms of $O$

Then, $6.02\times 10^{24}$ $CO$ molecules contain $6.02\times 10^{24}$ atoms of $O$

$\Rightarrow$ no. of gram atoms of $O=\cfrac {6.02\times 10^{24}}{6.02\times 10^{23}}$

$=10gm$ atoms  $\longrightarrow 1$

As oxygen is a diatomic molecule.

No. of gm of molecules of oxygen=$\cfrac {10gm\quad atoms}{2\quad atoms/molecule}=5gm$ molecules

Therefore, the correct option is B.

The number of g-atom of oxygen in $6.02\times { 10 }^{ 24 }$ $CO$ molecule is

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. $1$

  2. $0.5$

  3. $5$

  4. $10$

Show answer
Correct Option: D
Explanation:

One molecule of $CO$ contains one oxygen atom
$\therefore 6.02\times { 10 }^{ 24 }\quad $ molecules of $CO$ contain $6.02\times { 10 }^{ 24 }$ oxygen atoms
$6.02\times { 10 }^{ 23 }$ atoms of oxygen $\equiv$ $1g$ atom of oxygen
$\therefore 6.02\times { 10 }^{ 24 }$ atoms of oxygen $\equiv$ $10g$ atom of oxygen.

At room temperature and pressure, two flasks of equal volumes are filled with $H _2$ and $SO _2$ separately. Particles which are equal in number, in the two flasks are:

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. atoms

  2. electrons

  3. molecules

  4. neutrons

Show answer
Correct Option: C
Explanation:

At a given volume at constant temperature and pressure, two gases have equal no. of moles 

hence, the no. of molecules will be same in both flasks.

Which of the following statement about Avogadro's hypothesis is correct?

chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

  1. Under similar conditions of temperature and pressure, gases react with each other in simple ratio.

  2. Under similar conditions of temperature and pressure, equal volumes of all gases contain same number of molecules

  3. At NTP all gases contain same number of molecules

  4. Gases always react with gases only at the given temperature and pressure

Show answer
Correct Option: B
Explanation:

Avogadro’s Law states that under same conditions of temperature and pressure, equal volume of all the gases contain equal number of molecules.