Chemistry

Chemical Equilibrium and Stoichiometry

103 Questions

Chemical equilibrium and stoichiometry questions cover equilibrium constants, percent yield, and the Haber process. These concepts test your ability to calculate reaction outcomes and purity. Practice these to excel in physical chemistry sections of competitive tests.

Equilibrium constant calculationsStoichiometric yieldHaber processPercent purityHomogenous equilibrium

Chemical Equilibrium and Stoichiometry Questions

Multiple choice

A traditional chemist can synthesize _____________ compounds per year.

  1. 100-200

  2. 200-300

  3. 300-400

  4. 400-500
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Traditional synthetic chemists working manually can typically synthesize 100-200 new compounds per year. This estimate reflects the time-intensive nature of purification, characterization, and optimization required for each novel compound in classical synthetic workflows.

Multiple choice

For which of the following reactions is Kp equal to Kc?

  1. H2(g) + I2(g) <------> 2HI(g)

  2. 2C(s) + O2(g) <------> 2CO(g)

  3. N2(g) + 3H2(g) <------> 2NH3(g)

  4. CaCO3(s) <------> CaO(s) + CO2(g)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The relation between Kp and Kc is given as Kp = Kc(RT)∆ng………………∆ng is the difference between the number of moles of gaseous products and reactants.For this reaction ∆ng is 0. Hence Kp = Kc. Hence this is the correct answer.

Multiple choice

If K1, K2 be the equilibrium constants of two individual reactions and K3 is the equilibrium constant of a reaction obtained by addition of these two reactions, then correct relation between K1, K2 and K3 will be

  1. K3 = K1/K2

  2. K1 = K3/K2

  3. K1 = K2.K3

  4. K2 = K1.K3
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct as the given option may be written as K3  =  K1.K2And when two reactions are added to give the third reaction then equilibrium constant of the third reaction is always the product of the equilibrium constant of the individual reactions. 

Multiple choice

Which of the following is an example of homogenous equilibrium?

  1. Ca(OH)2(s) + H2O(aq) ⇌ Ca2+(aq) + 2OH- (aq)

  2. Ag2O(s) + 2HNO3(aq) ⇌ 2AgNO3(aq) + H2O(l)

  3. Fe3+(aq) + SCN-(aq) ⇌ Fe(SCN)2+(aq)

  4. Ni(s) + 4CO(g) ⇌ Ni(CO)4(g)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This answer is correct because all the reactants and products are in the aqueous phase hence, represent homogenous equilibria.

Multiple choice

Using the following data 2CH4 (g) + 3O2 (g) → 2CO (g) + 4H2O (g); ΔG° = -1088 kJ CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g); ΔG° = -801 kJ Calculate ΔG° for the reaction 2 CO (g) + O2 (g) → 2CO2 (g)

  1. 1028 KJ

  2. -1028 KJ

  3. 514 KJ
    • 514 KJ

  5. -1889 KJ
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

2CH4 (g) + 3O2 (g) → 2CO (g) + 4H2O (g) ΔG° = -1088 kJ  (Eq. 1) CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g); ΔG° = -801 kJ     (Eq. 2)

Reversed Eq. 1 2CO (g) + 4H2O (g) →2CH4 (g) + 3O2 (g); ΔG° = -(-1088 kJ) (Eq. 3) 2 x Eq. 2 2CH4 (g) + 4O2 (g) → 2CO2 (g) + 4H2O (g); ΔG° = 2 x (-801 kJ) (Eq. 4) On adding eq. 3 and eq. 4, we get 2CO (g) + O2 (g) → 2CO2 (g); ΔG° = -(-1088 kJ) - 2 x (-801 kJ) = -514 KJ

Multiple choice

The Kp for the formation of ammonia at 250 0C is 1.42x10-5 atm. Find the Kc for this reaction.

  1. 0.057

  2. 0.0057

  3. 0.57

  4. 0.66
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The equation for the above reaction is

N2  + 3H2 -----------------> 2NH3   (Δ n = 2 - (1+3)  = -2)

Kp = 1.42x10-5

T = 273 + 500

     = 773 K

R = 0.0821 L.atm/mol.K

By substituting the values in the following expression, we have

Kc = Kp/ (RT) Δ n

1.42x10-5/ (0.0821 x 773)-2 = 0.057

Multiple choice

Consider the following equilibrium SO2 (g) + ½ O2 (g) ⇌ SO3 (g), $\Delta$H = –23.5 kCal mo1–1 The formation of SO3 is favoured by

  1. compression and decreasing the temperature

  2. compression and increasing the temperature

  3. expansion and increasing the temperature

  4. expansion and decreasing the temperature
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The reaction is exothermic (delta H < 0) and involves a decrease in moles of gas (1.5 moles to 1 mole). According to Le Chatelier's principle, decreasing temperature favors the exothermic direction, and increasing pressure (compression) favors the side with fewer moles of gas.

Multiple choice reactions of acids and bases properties of acids and bases acids, bases and salts acids and bases chemistry

Ist & IInd dissociation const. for oxalic acid is $K _{1}$  and $K _{2}$  which is right statement is : 

  1. $K _{2}$ ,$K _{1}$ are equal
  2. $K _{2}$ is 1000 times greater thean $K _{1}$
  3. $K _{2}$ is $\frac{1}{1000}$ time than $K _{1}$

  4. All correct
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Oxalic acid H2C2O4 is a diprotic acid. The first dissociation (H2C2O4 → HC2O4- + H+) is easier than the second (HC2O4- → C2O4²- + H+) because removing H+ from a negatively charged species (HC2O4-) is harder. K2 is typically 1/1000 of K1.

Multiple choice botany photosynthesis action spectrum and absorption spectrum spectrum of electromagnetic radiation chloroplast and pigments of photosynthesis site of photosynthesis

Amount of $ C{ O} _{ 2 } $ mixed  annually is about 

  1. $70\times 1{ 0 }^{10 } Kg $
  2. $ 70\times 1{ 0 }^{11 } Kg$
  3. $ 70\times 1{ 0 }^{13 } Kg $
  4. $ 70\times 1{ 0 }^{13 } g $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

David Keeling started measuring the annual CO2 production from an observatory in Hawaii. He found the amount to be $70\times 1 { 0 } ^ { 10 } Kg$.
So, the correct option is '$70\times 1 { 0 } ^ { 10 } Kg$'

Multiple choice chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

${N} _{2}(g)+3{H} _{2}(g)\rightleftharpoons 2{NH} _{3}(g)+heat$
For the reaction above, what is the effect on the equilibrium position when the pressure is decreased?

  1. Increased production of products

  2. Increased production of reactants

  3. Fluctuations in the amounts of reactants and products

  4. No impact on the equilibrium

  5. Cannot be determined
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The given reaction is :-

${ N } _{ 2 }\left( g \right) +3{ H } _{ 2 }\left( g \right) \rightleftharpoons 2{ NH } _{ 3 }\left( g \right) +heat$
In this equilibrium, the forward reaction is accompanied by decrease in total no. of moles of gaseous species. If pressure on the system is decreased, the equilibrium shifts to the direction in which no. of moles increases as per Le Chatelier's principle. So, the backward reaction is favoured and reactants production is increased.

Multiple choice chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

Which of the following statements is incorrect ?

  1. In equilibrium mixture of ice water kept in perfectly insulated flask mass of ice and water does not change with time .

  2. The intensity of red colour increase when oxalic acid is added to a solution containing iron (III) nitrate and potassium thioyanate .

  3. On addition of catalyst equilibrium constant value is not affected .
  4. Equilibrium constant for a reaction with negative $\triangle H$ value decreases as the temperature increases .
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Adding oxalic acid to a solution containing iron(III) nitrate and potassium thiocyanate forms stable Fe-oxalate complexes, which consumes free Fe3+ ions. According to Le Chatelier's principle, this shifts the equilibrium for the formation of the red iron-thiocyanate complex backward, causing the red color to fade, not increase. Thus, statement B is incorrect.

Multiple choice chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

Two flasks A and B of an equal volume containing 1 mole and 2 moles of O$ 3$ respectively are heated to the same temperature. When the reaction $2O _3 \rightleftharpoons 3O _2$ practically stops, then both the flasks shall have __________.

  1. the same ratio: $[O _2]/[O _3]$
  2. the same ratio: $[O _2]^{3/2}/[O _3]$
  3. only $O _2$

  4. the same time to reach equilibrium
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For the given reaction,
$K _c = \displaystyle \frac{[O _2]^3}{[O _3]^2}= constant$     so  $\displaystyle \sqrt{K _c} = \frac{[O _2]^{3/2}}{[O _3]} = constant$
Same for both containers. Kc won't change as flasks are heated to same temperature. 

Multiple choice chemistry chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction

The approach to the following equilibrium was observed kinetically from both directions:
$ Pt{ Cl } _{ 4 }^{ -2 }+H _{ 2 }O\rightleftharpoons Pt(H _{ 2 }O)CI _{ 3 }+Cl^{ - } $
At $ 25^o C,$  it was found that  $ -\dfrac { d[PtC{ l } _{ 4 }^{ 2- }] }{ dt } =(3.9  \times 10^{ -5 } s^{ -1 }) [PtC{ l } _{ 4 }^{ 2- }]-(2.1  \times 10^{ -3 } L mol^{ -1 }s^{ -1 }) [Pt(H _{ 2 }O)C{ l } _{ 3 }^{ - }][Cl^{ - }] $
The value of $ K _{eq} $ (equilibrium constant) for the complexation of the fourth $ cl^- $ by $ Pt( II ) $ is

  1. $ 53.8 mol L^{-1} $
  2. $ 0.018 mol L^{-1} $
  3. $ 53.8 L mol^{-1} $
  4. $ 0.018 L mol^{-1} $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At equilibrium, the rate of the forward reaction equals the rate of the backward reaction. Setting the two rate expressions equal: (3.9e-5)[PtCl4^2-] = (2.1e-3)[Pt(H2O)Cl3^-][Cl^-]. The equilibrium constant Keq = [Pt(H2O)Cl3^-][Cl^-] / [PtCl4^2-] = 3.9e-5 / 2.1e-3 = 0.01857. The question asks for the complexation of the fourth Cl-, which is the reverse of the given reaction, so K = 1/0.01857 = 53.8.