Chapter 6. Equilibrium

Class 11 Chemistry Chapter 6 Equilibrium Internal Questions and Answers :

Problem 6.1 :  The following concentrations were obtained for the formation of from  and  at equilibrium at 500K.

 M ,  M and  M . Calculate equilibrium constant.

Problem 6.2 : At equilibrium, the concentrations of   M,  M and  M in a sealed vessel at 800K. What will be  for the reaction

Problem 6.3 :   ,  and  are at equilibrium at 500 K and having concentration 1.59M  , 1.59M  and 1.41 M  . Calculate  for the reaction,   

Problem 6.4 : The value of  at 800K for the reaction, .Calculate equilibrium concentrations of  , ,  and  at 800 K, if only  and  are present initially at concentrations of 0.10M each.

Problem 6.5 : For the equilibrium,  the value of the equilibrium constant,  is  at 1069 K. Calculate the   for the reaction at this temperature?

Problem 6.6 :  The value of  for the reaction, is 3.0 at 1000 K. If initially  bar and  bar and pure graphite is present, calculate the equilibrium partial pressures of  and  .

Problem 6.7 : The value of  for the reaction,  is   . At a given time, the composition of reaction mixture is  M. In which direction the reaction will proceed?

Problem 6.8 :  13.8g of  was placed in a 1L reaction vessel at 400K and allowed to attain equilibrium ,

The total pressure at equilbrium was found to be 9.15 bar. Calculate  and partial pressure at equilibrium .

Problem 6.9 : 3.00 mol of  kept in 1L closed reaction vessel was allowed to attain equilibrium at 380K. Calculate composition of the mixture at equilibrium. = 1.80

Problem 6.10 :  The value of  for the phosphorylation of glucose in glycolysis is 13.8 kJ/mol. Find the value of  at 298 K.

Problem 6.11 : Hydrolysis of sucrose gives,

Equilibrium constant  for the reaction is  at 300K. Calculate  at 300K.

Problem 6.12 : What will be the conjugate bases for the following Brönsted acids: ,  and  ?

Problem 6.13 :  Write the conjugate acids for the following Brönsted bases:   and   .

Problem 6.14 : The species:  ,  ,  and  can act both as Bronsted acids and bases. For each case give the corresponding conjugate acid and conjugate base.

Problem 6.15 : Classify the following species into Lewis acids and Lewis bases and show how these act as such:   (a)   (b)    (c)   (d)

Problem 6.16 :  The concentration of hydrogen ion in a sample of soft drink is  M. what is its pH ?

Problem 6.17 :  Calculate pH of a  M solution of HCl .

Problem 6.18 :  The ionization constant of HF is  . Calculate the degree of dissociation of HF in its 0.02 M solution. Calculate the concentration of all species present (  ,  and HF) in the solution

and its pH .

Problem 6.19 :  The pH of 0.1M monobasic acid is 4.50. Calculate the concentration of species  , and  at equilibrium. Also, determine the value of  and   of the monobasic acid.

Problem 6.20 : Calculate the pH of 0.08M solution of hypochlorous acid, . The ionization constant of the acid is  . Determine the percent dissociation of .

Problem 6.21 : The pH of 0.004M hydrazine solution is 9.7. Calculate its ionization constant  and  .

Problem 6.22 :  Calculate the pH of the solution in which 0.2M  and 0.1M  are present. The  of ammonia solution is 4.75.

Problem 6.23 : Determine the degree of ionization and pH of a 0.05M of ammonia solution. The ionization constant of ammonia can be taken from Table 6.7. Also, calculate the ionization constant of the conjugate acid of ammonia.

Problem 6.24 :  Calculate the pH of a 0.10M ammonia solution. Calculate the pH after 50.0 mL of this solution is treated with 25.0 mL of 0.10M HCl. The dissociation constant of ammonia,   

Problem 6.25 : The  of acetic acid and  of ammonium hydroxide are 4.76 and 4.75 respectively. Calculate the pH of ammonium acetate solution.

Problem 6.26 :  Calculate the solubility of  in pure water, assuming that neither kind of ion reacts with water. The solubility product of  ,  .

Problem 6.27 : The values of  of two sparingly soluble salts  and  are   and respectively. Which salt is more soluble? Explain.

Problem 6.28 :  Calculate the molar solubility of  in 0.10 M . The ionic product of  is    .

Class 11 Chemistry Chapter 6 Equilibrium Exercise Questions and Answers :

6.1 A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.

a) What is the initial effect of the change on vapour pressure?

b) How do rates of evaporation and condensation change initially?

c) What happens when equilibrium is restored finally and what will be the final vapour pressure?

6.2 What is Kc for the following equilibrium when the equilibrium concentration of each substance is:   and  ?

6.3 At a certain temperature and total pressure of 10 5 Pa, iodine vapour contains 40% by volume of  atoms

   

Calculate  for the equilibrium.

6.4 Write the expression for the equilibrium constant,  for each of the following reactions:

6.5 Find out the value of K c for each of the following equilibria from the value of :

6.6 For the following equilibrium,  at 1000 K

     

Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is  , for the reverse reaction?

6.7 Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?

6.8 Reaction between  and  takes place as follows:

     

If a mixture of 0.482 mol  and 0.933 mol of  is placed in a 10 L reaction vessel and allowed to form  at a temperature for which  , determine the composition of equilibrium mixture.

6.9 Nitric oxide reacts with  and gives nitrosyl bromide as per reaction given below:

   

When 0.087 mol of  and 0.0437 mol of  are mixed in a closed container at constant temperature, 0.0518 mol of  is obtained at equilibrium. Calculate equilibrium amount of  and  .

6.10 At 450K,  /bar for the given reaction at equilibrium.

  

What is  at this temperature ?

6.11 A sample of (g) is placed in flask at a pressure of 0.2 atm. At equilibrium the partial pressure of (g) is 0.04 atm. What is  for the given equilibrium ?

    

6.12 A mixture of 1.57 mol of  , 1.92 mol of  and 8.13 mol of  is introduced into a 20 L reaction vessel at 500 K. 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?

6.13 The equilibrium constant expression for a gas reaction is,

      

Write the balanced chemical equation corresponding to this expression.

6.14 One mole of  and one mole of  are taken in 10 L vessel and heated to 725 K. At equilibrium 40% of water (by mass) reacts with  according to the equation,

     

Calculate the equilibrium constant for the reaction.

6.15 At 700 K, equilibrium constant for the reaction:   is 54.8. If 0.5 mol  of (g) is present at equilibrium at 700 K, what are the concentration of (g) and  (g) assuming that we initially started with (g) and allowed it to reach equilibrium at 700K ?

6.16 What is the equilibrium concentration of each of the substances in the equilibrium when the initial concentration of  was 0.78 M ?

6.17   atm at 899 K 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?

6.18 Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is represented as:

 

(i) Write the concentration ratio (reaction quotient),  , for this reaction (note: water is not in excess and is not a solvent in this reaction)

(ii) At 293 K, if one starts with 1.00 mol of acetic acid and 0.18 mol of ethanol, there is 0.171 mol of ethyl acetate in the final equilibrium mixture. Calculate the equilibrium constant.

(iii) Starting with 0.5 mol of ethanol and 1.0 mol of acetic acid and maintaining it at 293 K, 0.214 mol of ethyl acetate is found after sometime. Has equilibrium been reached?

6.19 A sample of pure  was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of  was found to be  mol  . If value of  is  , what are the concentrations of   and  at equilibrium?

  

6.20 One 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  .

      ;   atm at 1050K

What are the equilibrium partial pressures of  and  at 1050 K if the initial partial pressures are:  atm and  atm?

6.21 Equilibrium constant,  for the reaction

        at 500 K is 0.061

At a particular time, the analysis shows that composition of the reaction mixture is 3.0 mol  , 2.0 mol and 0.5 mol  . Is the reaction at equilibrium? If not in which direction does the reaction tend to proceed to reach equilibrium?

6.22 Bromine monochloride,  decomposes into bromine and chlorine and reaches the equilibrium:   for which  at 500 K. If initially pure  is present at a concentration of  mol  , what is its molar concentration in the mixture at equilibrium?

6.23 At 1127 K and 1 atm pressure, a gaseous mixture of  and  in equilibrium with soild carbon has 90.55%  by mass

  

Calculate for this reaction at the above temperature.

6.24 Calculate a) and b) the equilibrium constant for the formation of  from  and  at 298K

   

Where   kJ/mol

  kJ/mol

  kJ/mol

6.25 Does 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?

(a) 

(b) 

(c) 

6.26 Which 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.

(i) 

(ii) 

(iii) 

(iv) 

(v) 

(vi) 

6.27 The equilibrium constant for the following reaction is  at 1024K

  

Find the equilibrium pressure of all gases if 10.0 bar of  is introduced into a sealed container at 1024K.

6.28 Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:

  

 (a) Write as expression for  for the above reaction.

(b) How will the values of  and composition of equilibrium mixture be affected by

(i) increasing the pressure

(ii) increasing the temperature

(iii) using a catalyst?

6.29 Describe the effect of:

(a) addition of

(b) addition of

(c) removal of

(d) removal of  on the equilibrium of the reaction:

         

6.30 At 473 K, equilibrium constant  for decomposition of phosphorus pentachloride, PCl 5 is   . If decomposition is depicted as,

       ;   kJ

a) Write an expression for  for the reaction.

b) What is the value of  for the reverse reaction at the same temperature?

c) What would be the effect on  if (i) more  is added (ii) pressure is increased

(iii) the temperature is increased ?

6.31 Dihydrogen 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  and  . In second stage,  formed in first stage is reacted with more steam in water gas shift reaction,

 

If a reaction vessel at 400 °C is charged with an equimolar mixture of  and steam such that  bar, what will be the partial pressure of  at equilibrium?   at 400°C

6.32 Predict which of the following reaction will have appreciable concentration of reactants and products:

(a) 

(b)

(c)

6.33 The value of  for the reaction  is  at 25°C. If the equilibrium concentration of  in air at 25°C is  , what is the concentration of  ?

6.34 The reaction,  is at equilibrium at 1300 K in a 1L flask. It also contain 0.30 mol of , 0.10 mol of  and 0.02 mol of  and an unknown amount of  in the flask. Determine the concentration of  in the mixture. The equilibrium constant,  for the reaction at the given temperature is 3.90.

6.35 What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species:

6.36 Which of the followings are Lewis acids?   and

6.37 What will be the conjugate bases for the Brönsted acids:  and ?

6.38 Write the conjugate acids for the following Brönsted bases:  and

6.39 The species:  ,  ,  and  can act both as Brö nsted acids and bases. For each case give the corresponding conjugate acid and base.

6.40 Classify the following species into Lewis acids and Lewis bases and show how these act as Lewis acid/base: (a)  (b)  (c)   (d)  .

6.41 The concentration of hydrogen ion in a sample of soft drink is  M. What is its  ?

6.42 The  of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in it.

6.43 The ionization constant of ,  and  at 298K are  ,  and  respectively. Calculate the ionization constants of the corresponding conjugate base.

6.44 The ionization constant of phenol is  . What is the concentration of phenolate ion in 0.05 M solution of phenol? What will be its degree of ionization if the solution is also 0.01M in sodium phenolate?

6.45 The first ionization constant of   is . Calculate the concentration of  ion in its 0.1M solution. How will this concentration be affected if the solution is 0.1M in  also? If the second dissociation constant of  is  , calculate the concentration of  under both conditions.

6.46 The ionization constant of acetic acid is   . Calculate the degree of dissociation of acetic acid in its 0.05 M solution. Calculate the concentration of acetate ion in the solution and its  .

6.47 It 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   .

6.48 Assuming complete dissociation, calculate the  of the following solutions:

(a) 0.003 M HCl (b) 0.005 M NaOH (c) 0.002 M HBr (d) 0.002 M KOH

6.49 Calculate the  of the following solutions:

a) 2 g of TlOH dissolved in water to give 2 litre of solution.

b) 0.3 g of  dissolved in water to give 500 mL of solution.

c) 0.3 g of NaOH dissolved in water to give 200 mL of solution.

d) 1mL of 13.6 M HCl is diluted with water to give 1 litre of solution.

6.50 The degree of ionization of a 0.1M bromoacetic acid solution is 0.132. Calculate the   of the solution and the  of bromoacetic acid.

6.51 The  of 0.005M codeine ( ) solution is 9.95. Calculate its ionization constant and  .

6.52 What 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.

6.53 Calculate 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 ?

6.54 The 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?

6.55 Calculate the hydrogen ion concentration in the following biological fluids whose  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.

6.56 The  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.

6.57 If 0.561 g of KOH is dissolved in water to give 200 mL of solution at 298 K. Calculate the concentrations of potassium, hydrogen and hydroxyl ions. What is its  ?

6.58 The solubility of  at 298 K is 19.23 g/L of solution. Calculate the concentrationsn of strontium and hydroxyl ions and the  of the solution.

6.59 The ionization constant of propanoic acid is  . Calculate the degree of ionization of the acid in its 0.05M solution and also its  . What will be its degree of ionization if the solution is 0.01M in HCl also?

6.60 The  of 0.1M solution of cyanic acid () is 2.34. Calculate the ionization constant of the acid and its degree of ionization in the solution.

6.61 The ionization constant of nitrous acid is  . Calculate the  of 0.04 M sodium nitrite solution and also its degree of hydrolysis.

6.62 A 0.02M solution of pyridinium hydrochloride has   . Calculate the ionization constant of pyridine.

6.63 Predict if the solutions of the following salts are neutral, acidic or basic:

    , ,  ,  ,  and

6.64 The ionization constant of chloroacetic acid is  . What will be the  of 0.1M acid and its 0.1M sodium salt solution?

6.65 Ionic product of water at 310 K is . What is the  of neutral water at this temperature?

6.66 Calculate the pH of the resultant mixtures:

a) 10 mL of 0.2M  + 25 mL of 0.1M HCl

b) 10 mL of 0.01M  + 10 mL of 0.01M

c) 10 mL of 0.1M  + 10 mL of 0.1M KOH

6.67 Determine 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.

6.68 The solubility product constant of  and  are  and   respectively. Calculate the ratio of the molarities of their saturated solutions.

6.69 Equal volumes of 0.002 M solutions of sodium iodate and cupric chlorate are mixed together. Will it lead to precipitation of copper iodate? (For cupric iodate  ).

6.70 The ionization constant of benzoic acid is  and  for silver benzoate is . How many times is silver benzoate more soluble in a buffer of   compared to its solubility in pure water?

6.71 What 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,  ).

6.72 What is the minimum volume of water required to dissolve 1g of calcium sulphate at 298 K? (For calcium sulphate,  is ).

6.73 The 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:  and . in which of these solutions precipitation will take place?