Chemistry

Mole Concept and Stoichiometry

365 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.

molecular mass calculationsstoichiometric conversionsmole fraction problemsheavy water reactionsoxidation calculations

Mole Concept and Stoichiometry Questions

Multiple choice

How many milligrams in a gram?

  1. 10

  2. 100

  3. 1000

  4. 10 000
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The metric system defines 1 gram as equal to 1000 milligrams. This is a standard unit conversion.

Multiple choice chemistry mix and separate different types of mixtures homogenous and heterogenous mixtures all about mixtures

Mixture of $MgCO _{3}$ & $NaHCO _{3}$ on strong heating gives $CO _{2}$ & $H _{2}O$ in $3 : 1$ mole ratio. The weight $\%$ of $NaHCO _{3}$ present in the mixture is :

  1. $30\%$
  2. $80\%$
  3. $40\%$
  4. $50\%$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Heating MgCO3 gives CO2, and heating NaHCO3 gives CO2 and H2O. Let x be moles of MgCO3 and y be moles of NaHCO3. The total CO2 is x + 0.5y and H2O is 0.5y. Given (x + 0.5y) / (0.5y) = 3/1, we find x = y. Calculating the mass percentage based on molar masses (MgCO3=84, NaHCO3=84) leads to 50%.

Multiple choice physics units and measurement: error analysis significant figures significant figures and rounding of digits units and measurements

A packet contains silver powder of mass $20.23g\pm 0l01g$. Some of the powder of mass $5.75g\pm 0.01g$ is taken out from it. The mass of the powder left back is

  1. $14.48g\pm 0.00g$
  2. $14.48g\pm 0.02g$
  3. $14.5g\pm 0.1g$
  4. $14.5g\pm 0.2g$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When subtracting values, the absolute uncertainties are added. 20.23 - 5.75 = 14.48, and 0.01 + 0.01 = 0.02.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

$2.33$g of compound X(empirical formula $CoH _{12}N _4Cl _3)$ upon treatment with excess $AgNO _3$ solution produces $1.435$g of a white precipitate. The primary and secondary valences of cobalt in compound X, respectively, are.
[Given : Atomic mass: $Co=59, Cl=35.5, Ag=108$].

  1. $3, 6$
  2. $3, 4$
  3. $2, 4$
  4. $4, 3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since $0.01$ mole of $X$ produces $0.01$ mole of $AgCl$,hence one $Cl^-$ is out of coordination sphere or complex is $[CO(NH _3) _4Cl _2]Cl$ AND HENCE $CO(3+)$,has $6$ coordination number

Multiple choice chemistry surface chemistry enzyme catalysis catalysis proteins and enzymes

Determine the surface area of a catalyst that adsorbs $10^3cm^3$ nitrogen at STP per gram in order to form mono layer. The effective area occupied by nitrogen molecule on the surface is $0.1602\times { 10 }^{ -14 }\quad { cm }^{ 2 }$

  1. $579m^2$
  2. $449 m^2$
  3. $579cm^2$

  4. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Volume of N2 gas = 10^3 cm^3 = 1000 cm^3 at STP. Number of moles = 1000 / 22400 = 0.0446 mol. Number of molecules = 0.0446 * 6.022 * 10^23 = 2.686 * 10^22 molecules. Total surface area = (Number of molecules) * (Area per molecule) = 2.686 * 10^22 * 0.1602 * 10^-14 cm^2 = 4.303 * 10^7 cm^2 = 4303 m^2, which does not match any of the provided numerical options (579 m^2, 449 m^2, 579 cm^2), making none of these correct.

Multiple choice chemistry nitrogen and sulfur ammonia and fertilizers preparation of ammonia-laboratory method and haber's process ammonia

$NH _3$ is formed in the following steps
I. $Ca+2C\rightarrow CaC _2$    50% yield
II. $CaC _2+N _2\rightarrow CaCN _2+C$   100% yield
III. $CaCN _2+3H _2O\rightarrow 2NH _3+CaCO _3$        50% yield
To obtain 2 moles $NH _3$, calcium required is:

  1. 1 mol

  2. 2 mol

  3. 3 mol

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

It can be easily observed from the reaction given that 1mole of Ca is required to get 2 moles of $NH _3$

Multiple choice chemistry nitrogen and sulfur ammonia and fertilizers preparation of ammonia-laboratory method and haber's process ammonia

In Haber's process $50.0\ g$ of $N _{2}(g)$ and $10.0\ g$ of $H _{2}(g)$ are mixed to produced $NH _{3}(g)$. What are the number of moles of $NH _{3}(g)$ formed?

  1. $3.33$
  2. $2.36$
  3. $2.01$
  4. $5.36$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$N _2 + 3H _2 \rightarrow2NH3$
Here.
28 g $N _2$ reacts with 6 g of $H _2$
So,
50 g of $N _2$ react with $\dfrac{6}{28}\times50 g -H _2 = 10.7 g$ but we have only 10g so $H _2$ is limiting reagent..

6 g $H _2$ gives 34g $NH _3$
10g $H _2$ will give $\dfrac{34}{6}\times10=56.67g -NH _3$
So number of moles of $NH _3$ formed is,
$=\dfrac{Given-mass}{Molar-mass}=\dfrac{56.67}{17}=3.33-moles$
Multiple choice

What is the chemical formula for carbon dioxide?

  1. CO2

  2. CH4

  3. H2O

  4. O2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical formula for carbon dioxide is CO2.

Multiple choice

What is the chemical formula for carbon dioxide?

  1. CO2

  2. CH4

  3. NH3

  4. O2

  5. H2O
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemical formula for carbon dioxide is CO2.

Multiple choice

What is the chemical formula for methane?

  1. CO2

  2. CH4

  3. NH3

  4. O2

  5. H2O
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The chemical formula for methane is CH4.

Multiple choice

What is the chemical formula for ammonia?

  1. CO2

  2. CH4

  3. NH3

  4. O2

  5. H2O
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The chemical formula for ammonia is NH3.

Multiple choice

What is the chemical formula for nitrogen?

  1. CO2

  2. CH4

  3. NH3

  4. O2

  5. N2
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The chemical formula for nitrogen is N2.

Multiple choice

What is the chemical formula for carbon monoxide?

  1. CO2

  2. CH4

  3. CO

  4. O2

  5. H2O
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The chemical formula for carbon monoxide is CO.