Chemistry

Mole Concept and Stoichiometry

354 Questions

The mole concept is a core area of chemistry focusing on the quantitative relationships between reactants and products in chemical reactions. Questions cover molecular mass calculations, stoichiometric conversions, and determining the number of molecules. This topic is essential for most science entrance and competitive examinations.

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Mole Concept and Stoichiometry Questions

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

Statement 1: The number of gram molecules of oxygen in $6.02 \times 10^{24}\ CO$ molecules is 5.0.
Statement 2: The value of Avogadro number is $6.02 \times 10^{23}$

  1. Statement 1 is True, statement 2 is True, Statement 2 is a correct explanation of statement 1.

  2. Statement 1 is True, statement 2 is True, Statement 2 is not a correct explanation of statement 1.

  3. Statement 1 is True, Statement 2 is False.

  4. Statement 1 is False, Statement 2 is True.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$6.02\times 10^{24}$ molecules of $CO=6.02\times 10^{23}\times 10$ i.e.., 10 moles of CO.
10 moles of CO contains 10 gm atoms of oxygen i.e.  5 gm molecules of oxygen.
hence the correct answer is A the given assertion is correct and reason is the correct explanation to the assertion.

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

14 g of nitrogen contains $3.01 \times 10^{23}$ nitrogen molecules.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

1 mole nitrogen contains $6.02\times10^{23}$ nitrogen molecules.

Thus 14 gram nitrogen will contain $14/28.Na=0.5Na=3.01\times10^{23}$ nitrogen molecules. ( Molecular weight of nitrogen is 28)

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

What is the mass of $6.022\times { 10 }^{ 23 }$ molecules of ${NH} _{3}$?

  1. $45.06g$
  2. $19.06\ g$
  3. $17.04g$
  4. $31.02g$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$1\space mole$ of $NH _3$ has $6.023 \times 10^{23}$ molecules of $NH _3$.

So, the mass of $6.023 \times 10^{23}$ molecules of $NH _3$. is the mass of $1\space mole$ of $NH _3$  i.e. molar mass of $NH _3.$ 
Molar mass $= 14.01 + 3(1.01) = 17.04 \space g$

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

How many molecules of water are present in a $0.25\ mole$ of $H _2O$?

  1. $6.0\times{10}^{22}$
  2. $4.5\times 10^{23}$
  3. $1.5\times{10}^{23}$
  4. $18\times 10^{23}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$1\space mole$ of a compound has $6.023\times 10^{23}$ molecules in it.

$\Rightarrow 1\space mole =$$6.023\times 10^{23}$ molecules
$ 0.25\space mole = x$ molecules
$\Rightarrow x = (\dfrac{6.023}{4}) \times 10^{23}$$= 1.5\times 10^{23}$ molecules of water.

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

How many atoms of hydrogen are present in $7.8\ g$ of $Al{(OH)} _{3}$?

  1. $6.0\times {10}^{22}$
  2. $1.8\times {10}^{23}$
  3. $1.7\times {10}^{23}$
  4. $5.1\times {10}^{22}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Molar mass of $Al(OH) _3 = 27 + 3\times 16 + 3\times 1 = 78\space g$

So, no. of moles of $Al(OH) _3 = \dfrac{7.8}{78} = 0.1\space moles$
$1\space mole$ of $Al(OH) _3$ has $6.023 \times 10^{23}$ atoms.
So, $0.1\space moles$ has $6.023 \times 10^{22}$ atoms.

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 quantitative chemistry avogadro hypothesis avogadro's law avogadro law

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 _________?

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

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

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

  1. 10 gm molecules

  2. 5 gm molecules

  3. 1 gm molecules

  4. 0.5 gm molecules
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  1. $1$
  2. $0.5$
  3. $5$
  4. $10$
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

The charge required to deposit 40.5 g of Al(atomic mass=27.0 g) from the fused ${ Al } _{ 2 }{ \left( { SO } _{ 4 } \right) } _{ 3 }$ is :

  1. $4.34\times { 10 }^{ 5 }C$
  2. $43.4\times { 10 }^{ 5 }C$
  3. $1.44\times { 10 }^{ 5 }C$

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The reaction is Al^3+ + 3e- -> Al. 1 mole of Al (27g) requires 3 Faradays (3 * 96500 C). For 40.5g, the moles of Al = 40.5 / 27 = 1.5 moles. Charge = 1.5 * 3 * 96500 = 4.5 * 96500 = 434250 C, which is 4.34 * 10^5 C.

Multiple choice imperfections in solids solid state the solid state chemistry

The composition of a sample of iron oxide is $Fe _{0.93}O _{1.0}$. What percentage of iron is present in the form of Fe(III)?

  1. $5.053$
  2. $10.053$
  3. $15.053$

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the percentage amount of Fe(III) be x and the amount of Fe(II) be $1-x$. Hence,  
$3x+2(1-x) = 2/0.93 = 2.15053$
On solving, we get, $x = 0.15053$
So, % of Fe(III) = 15.053

Multiple choice biology food and it's constituents energy giving food carbohydrate and its test biological molecules

The ratio between hydrogen and oxygen in carbohydrate is

  1. $5 : 1$
  2. $4 : 3$
  3. $3 : 1$
  4. $2 : 1$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Monosaccharide is the simplest form of carbohydrate which is composed of carbon, hydrogen and oxygen. The basic formula of the monosaccharide is C$ _n$H$ _{2n}$O$ _n$. These are considered as simplest form of sugar. The ratio between the hydrogen and oxygen is 2:1. For example, fructose is a monosaccharide with five carbon atom, ten hydrogen and five oxygen.
So, the correct answer is option D.
Multiple choice biology food and it's constituents energy giving food carbohydrate and its test biological molecules

How much energy is utilised in the synthesis of one gram mole of glucose?

  1. $673$ kcal
  2. $686$ kcal
  3. $666$ kcal
  4. $696$ kcal.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$686$ kcal energy is utilised in the synthesis of one gram mole of glucose. 

When $1$ mol of glucose means $180$ g of glucose reacts with oxygen under standard conditions, so $686$ kcal is released in the reaction.
Hence, the correct option is B.

Multiple choice chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

In the equation,


$4M + 8 CN^- + 2 H _2O + O _2 \longrightarrow 4[M(CN) _2]^- + 4 OH^-$

the metal M is:

  1. Copper

  2. Silver

  3. Gold

  4. Zinc
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

Cyanide process, also called Macarthur-Forrest Process, method of extracting silver and gold from their ores by dissolving them in a dilute solution of sodium cyanide or potassium cyanide. 


The process was invented in 1887 by the Scottish chemists John S. MacArthur, Robert W. Forrest, and William Forrest.

$4Ag + 8 CN^- + 2 H _2O + O _2 \longrightarrow 4[Ag(CN) _2]^- + 4 OH^-$


$4Au + 8 CN^- + 2 H _2O + O _2 \longrightarrow 4[Au(CN) _2]^- + 4 OH^-$


Hence options B & C are correct.

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

What is the density of an iron block which has a volume of ${12 cm^3}$ and a mass of 96g?

  1. ${ 8 kg/m ^3}$
  2. ${80 kg /m ^3}$
  3. ${8000 kg /m ^3}$
  4. ${800 kg/ m ^3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

As we know, Density $d = \dfrac{Mass, M}{ Volume, V}$


In this case, an iron block which has a volume of ${12 cm^3}$ = ${0.12 m^3}$ and a mass of $96 g = 0.096 kg$.

Therefore, Density $d =\dfrac{ 0.096}{0.12} = 8 kg/m^{ 3 }$.

Hence, the density of the iron block is 8 $kg/m^{ 3 }$.