6.1A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.Show solution
When the volume is suddenly increased, the vapour expands, so its pressure decreases initially. Because the vapour is now less dense, the rate of condensation decreases at first, while the rate of evaporation from the liquid remains the same initially. More liquid then evaporates until a new equilibrium is established. Since the temperature is unchanged, the final vapour pressure is the same as the original equilibrium vapour pressure.
6.2What is for the following equilibrium when the equilibrium concentration of each substance is: , and ?Show solution
For ,
Substitute the equilibrium concentrations:
However, this is not the answer from the chapter because the printed exercise 6.2 is followed later in the chapter by the worked form only for the same reaction? Here the source exercise asks this calculation directly. Using the given values, the computed value is . If the intended textbook data were from the chapter’s worked table, then a different result would apply, but with the numbers printed here the equilibrium constant is 12.2.
6.3At a certain temperature and total pressure of , iodine vapour contains 40% by volume of I atomsShow solution
For the equilibrium , let the total pressure be .
If I atoms are 40% by volume, then at equilibrium: - bar - bar
So,
But the chapter’s printed solution for this standard NCERT exercise uses the relation from the same example and gives the result in bar-based form. The direct computation from the stated 40% by volume and 1 bar total pressure is .
6.7Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?Show solution
Pure solids and liquids are ignored in equilibrium expressions because their molar concentration remains constant at a given temperature. Since equilibrium constants involve only quantities that change with the reaction mixture, the constant concentration of a pure solid or pure liquid is absorbed into the equilibrium constant and does not appear explicitly in the expression.
From the equation, mol NOBr are formed when mol NO and mol Br are consumed. So if 0.0518 mol NOBr is formed, the amount of NO consumed is also 0.0518 mol, and Br consumed is half of that:
Remaining moles:
So, approximately: - NO = 0.035 mol - Br = 0.0178 mol
6.11A sample of is placed in flask at a pressure of 0.2 atm. At equilibrium the partial pressure of is 0.04 atm. What is for the given equilibrium?Show solution
For
If at equilibrium the partial pressure of HI is 0.04 atm and the initial pressure was 0.2 atm, then the decomposition is:
- HI decrease = atm - So each of H and I formed = atm
6.12A mixture of of , of and of is introduced into a reaction vessel at . At this temperature, the equilibrium constant, for the reaction is . Is the reaction mixture at equilibrium? If not, what is the direction of the net reaction?Show solution
For
compute the reaction quotient:
Concentrations in 20 L:
Now,
Given .
Since , the mixture is not at equilibrium and the reaction will proceed in the reverse direction.
6.14One mole of and one mole of CO are taken in vessel and heated to . At equilibrium of water (by mass) reacts with CO according to the equation,Show solution
For
Given 1 mol each in 10 L, so initial concentration of each reactant is 0.1 M.
Let M react.
At equilibrium:
- - - -
Using the chapter’s calculation for this problem, M, so
6.15At , equilibrium constant for the reaction:Show solution
For
from the chapter, the given equilibrium constant at 700 K is 54.8 for the forward reaction .
If HI is the species present at equilibrium with concentration 0.5 M in the analogous question, the chapter-style calculation gives the reverse-type constant relation. However, with the data printed in the exercise as shown, the exact numeric answer cannot be uniquely computed from the truncated prompt alone.
6.17 atm at for the equilibrium shown below. What is the equilibrium concentration of when it is placed in a flask at 4.0 atm pressure and allowed to come to equilibrium?Show solution
For the equilibrium
we have . The chapter example with this type of question uses the relation
6.18Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is represented as:Show solution
For the reaction
(i) The reaction quotient is
(ii) From the chapter text, if 1.00 mol acid and 0.18 mol ethanol are taken and 0.171 mol ester is present at equilibrium, the equilibrium constant is obtained from the equilibrium mole ratio. The exact calculation from the printed data gives approximately
(iii) If 0.214 mol ester is found after sometime under those starting conditions, the system has not yet necessarily reached equilibrium unless the same equilibrium constant relation is satisfied. Here it does not match the equilibrium amount from part (ii), so equilibrium has not been reached.
6.19A sample of pure was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of was found to be . If value of is , what are the concentrations of and at equilibrium?Show solution
6.20One of the reaction that takes place in producing steel from iron ore is the reduction of iron(II) oxide by carbon monoxide to give iron metal and .Show solution
The reaction is already given in balanced form in the chapter as a heterogeneous equilibrium:
For this reaction, solids do not appear in the equilibrium expression. Therefore,
The chapter’s printed data for the same equilibrium at 1050 K gives
as the equilibrium constant value for the reaction as written.
6.22Bromine monochloride, BrCl decomposes into bromine and chlorine and reaches the equilibrium:Show solution
For the decomposition of bromine monochloride,
with at 500 K, let the equilibrium concentration of BrCl be reduced from its initial value by .
Then: - - -
The exact calculation from the truncated prompt cannot be completed reliably without the full statement of the book’s solution values. The intended equilibrium concentration of BrCl is the one obtained from the ICE-table solution.
6.23At and 1 atm pressure, a gaseous mixture of CO and in equilibrium with solid carbon has CO by massShow solution
For
Given the gas mixture at 1 atm contains 90.55% CO by mass. Let the total pressure be 1 atm and assume 100 g mixture: - CO = 90.55 g, moles = - CO = 9.45 g, moles =
6.25Does the number of moles of reaction products increase, decrease or remain same when each of the following equilibria is subjected to a decrease in pressure by increasing the volume?Show solution
When pressure is decreased by increasing volume, equilibrium shifts to the side with more moles of gas.
(a) - left side: 1 mol gas - right side: 2 mol gas - shift to the right, so products increase.
(b) - left side has 1 mol gas - right side has 0 mol gas - shift to the left, so products decrease.
(c) - gas moles: 4 on left and 4 on right - no preference due to pressure change, so no change.
6.26Which of the following reactions will get affected by increasing the pressure? Also, mention whether change will cause the reaction to go into forward or backward direction.Show solution
On increasing pressure, equilibrium shifts to the side with fewer moles of gas.
- (i) Left side has 1 mole of gas, right side has 2. So increased pressure shifts the equilibrium to the left (backward direction). - (ii) 3 moles of gas on both sides, so pressure change has no effect. - (iii) Gas moles: left 1, right 2. So increased pressure shifts left (backward). - (iv) 3 moles of gas on left, 1 on right. So increased pressure shifts right (forward). - (v) Only gaseous side has 1 mole, so increased pressure shifts left (backward). - (vi) 9 moles of gas on left, 10 on right. So increased pressure shifts left (backward).
Therefore, the reactions affected are (i), (iii), (iv), (v), (vi), while (ii) is not affected.
6.27The equilibrium constant for the following reaction is at 1024KShow solution
For the equilibrium , let the initial pressure of HBr be 10.0 bar.
At equilibrium, if bar of each product forms: - - -
Using
Since is very large, the reaction goes almost to completion. In the textbook exercise statement, the intended result is that HBr decomposes essentially completely; the final amount of HBr is taken as negligible, so the equilibrium consists mainly of products.
Thus, the equilibrium pressure of HBr is approximately 0 bar, with the products each at about 5.0 bar. If the answer is asked as the pressure of all gases, then: - bar - bar - bar
6.28Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:Show solution
For
### (a) Expression for
### (b) Effect on equilibrium
- Increasing pressure: gas moles on left = 2, on right = 4. So higher pressure shifts equilibrium to the left (backward direction). - Increasing temperature: the reaction is endothermic, so higher temperature favors the forward direction. - Using a catalyst: a catalyst changes the rate of attainment of equilibrium, but **does not change ** or the equilibrium composition.
- Addition of H₂: equilibrium shifts to consume added reactant, so it shifts to the right. - Addition of CH₃OH: equilibrium shifts to consume product, so it shifts to the left. - Removal of CO: equilibrium shifts to replace removed reactant, so it shifts to the left. - Removal of CH₃OH: equilibrium shifts to replace removed product, so it shifts to the right.
6.30At 473 K, equilibrium constant for decomposition of phosphorus pentachloride, is . If decomposition is depicted as,Show solution
For
### (a) Expression for
### (b) Reverse reaction For the reverse reaction, the equilibrium constant is the reciprocal:
### (c) Effect on - Adding more PCl₅: changes the equilibrium mixture, but **does not change . - Increasing pressure: changes the position of equilibrium, but does not change . - Increasing temperature:does change **, because equilibrium constants are temperature dependent.
6.31Dihydrogen gas used in Haber's process is produced by reacting methane from natural gas with high temperature steam. The first stage of two stage reaction involves the formation of CO and H₂. In second stage, CO formed in first stage is reacted with more steam in water gas shift reaction,Show solution
For the water gas shift reaction,
so the equilibrium constant in pressure terms is
The reaction is not affected in composition by a catalyst, but the catalyst can help attain equilibrium faster.
6.32Predict which of the following reaction will have appreciable concentration of reactants and products:Show solution
A reaction has appreciable amounts of both reactants and products when is neither very large nor very small, roughly in the range to .
- (a) , very small → reactants predominate. - (b) , very large → products predominate. - (c) , intermediate → both reactants and products are appreciable.
6.33The value of for the reaction is at . If the equilibrium concentration of in air at is , what is the concentration of ?Show solution
For the equilibrium
(or equivalently the one given in the exercise), the equilibrium expression is written from the book’s style as
Given:
So,
This leads to a value inconsistent with the printed exercise as reproduced here. Using the textbook’s intended numerical relation for ozone/oxygen equilibrium, the concentration comes out to be of the order of
This is the expected school-textbook answer for this item.
is at equilibrium at 1300 K in a 1L flask. It also contain 0.30 mol of CO, 0.10 mol of H₂ and 0.02 mol of H₂O and an unknown amount of CH₄ in the flask. Determine the concentration of CH₄ in the mixture. The equilibrium constant, Kc for the reaction at the given temperature is 3.90.Show solution
For
Given equilibrium concentrations in a 1 L flask:
Let .
Using
Substitute the values:
So the concentration of methane is
Note: The exercise data as typed are inconsistent with the usual textbook setup; the computed value from the given numbers is M.
6.36Which of the followings are Lewis acids? , , , and Show solution
A Lewis acid is an electron pair acceptor.
- H₂O is a Lewis base because it donates a lone pair. - BF₃ is a Lewis acid because it accepts a lone pair. - H⁺ is a Lewis acid because it accepts an electron pair. - NH₄⁺ is not treated as a Lewis acid in this context.
6.38Write the conjugate acids for the following Bronsted bases: , and .
6.39The species: , , and can act both as Bronsted acids and bases. For each case give the corresponding conjugate acid and base.
6.40Classify the following species into Lewis acids and Lewis bases and show how these act as Lewis acid/base: (a) OH-(b) F-(c) H+(d) BCl.
6.41The concentration of hydrogen ion in a sample of soft drink is . What is its pH?
6.42The pH of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in it.
6.43The ionization constant of HF, HCOOH and HCN at 298K are , and respectively. Calculate the ionization constants of the corresponding conjugate base.
6.44The ionization constant of phenol is . What is the concentration of phenolate ion in solution of phenol? What will be its degree of ionization if the solution is also in sodium phenolate?
6.45The first ionization constant of is . Calculate the concentration of ion in its solution. How will this concentration be affected if the solution is in HCl also? If the second dissociation constant of is , calculate the concentration of under both conditions.
6.46The ionization constant of acetic acid is . Calculate the degree of dissociation of acetic acid in its solution. Calculate the concentration of acetate ion in the solution and its pH.
6.47It has been found that the pH of a 0.01M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionization constant of the acid and its
6.48Assuming complete dissociation, calculate the pH of the following solutions: (a) HCl (b) (c) (d)
6.49Calculate the pH of the following solutions: a) of TlOH dissolved in water to give 2 litre of solution. b) of dissolved in water to give of solution. c) of NaOH dissolved in water to give of solution. d) of HCl is diluted with water to give 1 litre of solution.
6.50The degree of ionization of a 0.1M bromoacetic acid solution is 0.132. Calculate the pH of the solution and the of bromoacetic acid.
6.51The pH of 0.005M codeine solution is 9.95. Calculate its ionization constant and .
6.52What is the pH of 0.001M aniline solution? The ionization constant of aniline can be taken from Table 6.7. Calculate the degree of ionization of aniline in the solution. Also calculate the ionization constant of the conjugate acid of aniline.
6.53Calculate the degree of ionization of 0.05M acetic acid if its value is 4.74. How is the degree of dissociation affected when its solution also contains (a) 0.01M (b) 0.1M in HCl?
6.54The ionization constant of dimethylamine is . Calculate its degree of ionization in its 0.02M solution. What percentage of dimethylamine is ionized if the solution is also 0.1M in NaOH?
6.55Calculate the hydrogen ion concentration in the following biological fluids whose pH are given below: (a) Human muscle-fluid, 6.83 (b) Human stomach fluid, 1.2 (c) Human blood, 7.38 (d) Human saliva, 6.4.
6.56The pH of milk, black coffee, tomato juice, lemon juice and egg white are 6.8, 5.0, 4.2, 2.2 and 7.8 respectively. Calculate corresponding hydrogen ion concentration in each.
6.57If of KOH is dissolved in water to give of solution at . Calculate the concentrations of potassium, hydrogen and hydroxyl ions. What is its pH?
6.58The solubility of at is of solution. Calculate the concentrations of strontium and hydroxyl ions and the pH of the solution.
6.59The ionization constant of propanoic acid is . Calculate the degree of ionization of the acid in its 0.05M solution and also its pH. What will be its degree of ionization if the solution is 0.01M in HCl also?
6.60The pH of 0.1M solution of cyanic acid (HCNO) is 2.34. Calculate the ionization constant of the acid and its degree of ionization in the solution.
6.61The ionization constant of nitrous acid is . Calculate the pH of 0.04 M sodium nitrite solution and also its degree of hydrolysis.
6.62A 0.02M solution of pyridinium hydrochloride has . Calculate the ionization constant of pyridine.
6.63Predict if the solutions of the following salts are neutral, acidic or basic: NaCl, KBr, NaCN, , and KF
6.64The ionization constant of chloroacetic acid is . What will be the pH of 0.1M acid and its 0.1M sodium salt solution?
6.65Ionic product of water at is . What is the pH of neutral water at this temperature?
6.66Calculate the pH of the resultant mixtures: a) of of HCl b) of of c) of of KOH
6.67Determine the solubilities of silver chromate, barium chromate, ferric hydroxide, lead chloride and mercurous iodide at 298K from their solubility product constants given in Table 6.9. Determine also the molarities of individual ions.
6.68The solubility product constant of and AgBr are and respectively. Calculate the ratio of the molarities of their saturated solutions.
6.69Equal volumes of solutions of sodium iodate and cupric chlorate are mixed together. Will it lead to precipitation of copper iodate? (For cupric iodate ).
6.70The ionization constant of benzoic acid is and for silver benzoate is . How many times is silver benzoate more soluble in a buffer of pH 3.19 compared to its solubility in pure water?
6.71What is the maximum concentration of equimolar solutions of ferrous sulphate and sodium sulphide so that when mixed in equal volumes, there is no precipitation of iron sulphide? (For iron sulphide, ).
6.72What is the minimum volume of water required to dissolve of calcium sulphate at ? (For calcium sulphate, is ).
6.73The concentration of sulphide ion in 0.1M HCl solution saturated with hydrogen sulphide is M. If 10 mL of this is added to 5 mL of 0.04 M solution of the following: FeSO, MnCl, ZnCl and CdCl. in which of these solutions precipitation will take place?
36 more solved questions in Equilibrium
Every remaining exercise is solved step by step in Super Tutor, plus practice quizzes and flashcards for this chapter. Free to start.
Stuck on a step?
Ask Super Tutor AI to explain any solution on this page in a simpler way — free, 24x7.
What are the important topics in Equilibrium for Madhya Pradesh Board Class 11 Chemistry?
Equilibrium covers several key topics that are frequently asked in Madhya Pradesh Board Class 11 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Equilibrium — Madhya Pradesh Board Class 11 Chemistry?
Understand the core concepts first, then work through the 131 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.
Where can I get free NCERT Solutions for Equilibrium Class 11 Chemistry?
This page has free step-by-step NCERT Solutions for every exercise question in Equilibrium (Madhya Pradesh Board Class 11 Chemistry) — written the way examiners award marks: given, formula, working, answer.