EQUILIBRIUM

1. EQUILIBRIUM

An equilibrium represents a state in a process when the observable properties such as colour, temperature, pressure, concentration etc. do not show any change.
A. Types of equilibrium
Equilibrium is of two types
i. Physical equilibrium ii. Chemical equilibrium
Physical equilibrium
Equilibrium in physical processes is called physical equilibrium.
B. Chemical equilibrium
Equilibrium associated with chemical reaction is known as chemical equilibrium.
Types of physical equilibrium
Physical equilibrium is of three types
i. Solid-liquid equilibrium
Ice    water
Rate of melting = Rate of freezing
ii. Liquid-gas equilibrium
Water  vapours
Rate of vaporisation = Rate of condensation
iii. Solid-gas equilibrium
It occurs only in those solids which sublimise on heating.
For example: Ammonium chloride, iodine, camphor.

2. EQUILIBIUM RELATING TO DISSOLUTION OF SOLIDS IN LIQUIDS OR GASES IN LIQUIDS
Equilibrium between a solid and its solution is indicated by saturated solution.
Solubility
The maximum amount of the solute in grams which dissolves in 100 g of the solvent at a given temperature to form the saturated solution is known as the solubility. Solubility of the solid in solution is constant at constant temperature.
The equilibrium may be represented as
Sugar (in solution)  Sugar (solid)
Equilibrium between a gas and its solution in a liquid
The equilibrium may be represented as
(present in solution)
(Note)
Henry’s law
The mass of gas that dissolve in a given mass of a solvent at any temperature is proportional to the pressure of the gas above the surface of the solvent. Mathematically,
or  (k is a constant)


EXAMPLE
EXAMPLE:1 During bottling a carbonated beverage was made by saturating flavoured water at 00C with  at a pressure of 4.0 atm. Later, the bottle was opened and the soft drink is allowed to come at equilibrium at  with air containing  at a pressure of  atm. Find the concentration of  in the freshly bottled soda and in the soda after it had stood open and come to equilibrium. The Henry’s constant for aqueous solution of  are
At   mol
At  mol
SOLUTION: For opened bottled soft drink.

For freshly bottled soft drink



3. SOME GERNERALISATIONS ASSOCIATED WITH PHYSICAL EQUILIBRIA
A. Solid  liquid equilibrium is obtained only at a particular temperature. This temperature is the melting point of solid of freezing point of the liquid.
B. In liquid  gas equilibrium, the pressure of the vapours of the liquid above the liquid surface is called vapour pressure. It is constant at a given temperature. At equilibrium the molecules in two phases have equal kinetic energy. Addition of salt flowers the vapour pressure.
Some features of physical equilibrium
Process Conclusion
Liquid  Vapour
constant at given
temperature
Solid  Liquid
(s) Melting point is fixed at constant pressure
Solute (s) solute
(solution)
  Concentration of solute in solution is constant at a
Sugar  sugar
(solution)
given temperature
Gas (g) Gas (aq) [Gas (aq)]/[Gas (g)]
is constant at a given temperature
[ is constant at a given temperature.
4. GENERAL CHARACTESTICS OF EQUILIBRIA INVOLVING PHYSICAL PROCESS
A. At the equilibrium, the measurable properties of the system become constant.
B. The equilibrium is dynamic in nature.
C. The equilibria involving gases can be attained only in closed containers.
D. At equilibrium, the ratio of the species present in two different phases is constant at a constant temperature.
For example:
 System,
 constant
This is known as equilibrium constant.
E. At equilibrium, the concentrations of the different substances involved become constant at a constant temperature.
F. The value of equilibrium constant represent the extent to which the process proceeds before equilibrium is achieved.
5. EQUILIBRIUM IN CHEMICAL SYSTEMS
Chemical equilibrium can be attained in eversible chemical reactions carried in closed container. Gaseous species escape from an open vessel and the equilibrium cannot be attained.
Red Alert
At equilibrium, the rate of forward reaction becomes equal to the rate of backward reaction. At equilibrium state, Rate of forward reaction = Rate of backward reaction. It is shown graphically as follows:


6. HOMOGENEOUS AND HETEROGENEOUS REACTIONS    
Reactions in which all the reactants and products are in one phase is called homogeneous reaction.
For example:
Reaction in which the reactants and products are in more then one phase is called heterogeneous reaction.
For example:
7. CHARACTERSTICS OF CHEMICAL EQUILIBIUM
A. The observable properties of the system become constant once the equilibrium is reached.
B. The equilibrium is obtained only in the reactions carried in closed vessels.
C. The equilibrium is of dynamic nature.
D. A catalyst cannot alter the equilibrium point.
E. The free energy change at equilibrium state in zero.
F. In a reversible reaction, chemical equilibrium can be attained from either sides.
Check Your Grasp
1. A reaction reaches a state of chemical equilibrium only when
A. the reactants and the products are reacting
B. the concentrations of the reactants and products become equal.
C. The products react together at the same rate at which they are formed.
D. All the reactants and the products are in the same state of matter.
2. When  and  are mixed and equilibrium is attained, then
A. Amount of HI formed is equal to the amount of  dissociated
B. HI dissociation stops
C. reaction completes
D. none of these.
8. LAW OF MASS ACTION
According to law of mass action the rate of a reaction is directly proportional to the product of the molar concentrations (active masses) of the reactants with each concentration term raised to the power equal to the number of times that reactants appear in the balanced chemical equation.

According to law of mass action:
Rate of forward reaction,

Where  is rate constant for the forward reaction
Rate of backward reaction,
Where  is rate constant for the backward reaction. At equilibrium,
Rate of forward reaction = Rate of backward reaction.
7. In the equilibrium reaction involving the dissociation of
The equilibrium constant is given by
A. B.
C. D.
11. CHARACTERSTICS OF EQUILIBIUM CONSTANT
A. Variation of K with temperature
Equilibrium constant varies with temperature. Its variation with temperature can be described by the following relation

Where  Enthalpy change,  and Eequilibrium constant at temperature  and  respectively.
R= Universal gas constant. This equation is known as

Van’t Hoff equation.
B. The different form of above equation is

Note
C. Van’t Hoff reaction isotherm
It is an equation which gives the relationship between standard free energy change  of a reaction and its equilibrium constant
In
i. The value of the equilibrium constant does not depend upon the initial molar concentrations of the reactants and products. However, it depends upon their molar concentrations in the equilibrium state.
Addition if reactants or products donot change the value of the equilibrium constant.
ii. For a reversible reaction, the equilibrium constant for the backward reaction is inverse of the equilibrium constant for the forward reaction.
Red Alert  
D. Properties of K
i. When the equation is revered, the new equilibrium constant is 1/K.
ii. When equation is divided by 2, the new equilibrium constant is .
iii. When the equation is multiplied by 2, the new equilibrium constant is .
iv. When the equation is divided in two steps, the new equilibrium constant is
v. The value of equilibrium constant gives an idea about the extent to which a reaction has processed at a given temperature before equilibrium. is attained.
E. Estimation of extent of reaction:
Numerical value of equilibrium constant reflects that how far the reaction proceeds before the equilibrium state is reached.
i. If  products predominate over reactants. If  is very large, the reaction proceeds nearly to the completion.
ii. If , reactants predominate over products. If  is very small, the reaction proceeds hardly at all.
iii. If  is in the large  to  appreciable concentrations of both reactants and products are present.
EXAMPLE
EXAMPLE:4 .  For the equilibrium, . If the vapour pressure of water at  is 4.58 torr, at which relative humidities will  be deliquescent (absorb moisture) when exposed to the air at  essentially.
SOLUTION: We have


Or  atm
torr
Vapour pressure of water at  torr
Hydrate will efforesce below 2.77 torr or at
Relative humidity
So,  will be absorbing above 60.5 relative humidity.
TRICK
Prediction of relative amount of reactants and products on the basis of magnitude of equilibrium constant (K)
i. if  then, amount of reactant > amount of product
ii. If  then, amount of reactant <amount of product
iii. Lower the value of equilibrium constant greater will be the stability of the compound formed.
iv. The units of equilibrium constant depend upon the units in which the concentrations of the different species are expressed.
Check Your Grasp
8. The equilibrium constant in a reversible chemical reaction at a given temperature
A. depends on the initial concentration of the reactants
B. depends on the concentration of one of the products at equilibrium
C. does not depend on the initial concentrations of reactants
D. is not characteristic of the reaction.
9.  and  are the velocity constants of forward and backward reactions. The equilibrium constant K of the reaction is
A.   B.
C. D.
10. In the two gaseous reaction (i) and (ii), at
A.
B.
The equilibrium constants  and  are related as
A. B.
C. D.
12. FACTORS INFLUNCING THE STATE OF EQUILIBRIUM : LE-CHATELIER ‘S PRINCIPLE
According to this principle, “If a system is equilibrium is subjected to a change in any factor (temperature, pressure, concentration), which determine the equilibrium, the point of equilibrium is shifted in that direction which tends to nullify the effect of the change.”
A. Effect of change of temperature
i. The increase in temperature shifts the equilibrium in the direction of the endothermic reaction.
ii. The decrease in temperature shifts the equilibrium in the directions of the exothermic reaction.




Red Alert
Effect of temperature on equilibrium constant (K)
i. For endothermic reactions
When temperature is increased,  increases.
ii. For exothermic reactions
When temperature is increased,  decreases
iii.  For the reactions having zero heat of reaction, temperature has no effect on the value of K.
B. Effect of change of pressure
i. Increase in pressure shifts the equilibrium in the direction of decreasing gaseous moles.
ii. Decrease in pressure shifts the equilibrium in the direction of increasing gaseous moles.
iii. Pressure has no effect if the gaseous reactants and products have equal number of moles.
Check Your Grasp
11. For reaction at equilibrium, Le- Chatelier’s principle predicts the effects of
A. temperature and pressure
B. temperature and volume
C. pressure and volume
D. only volume
12. Which one of the following information’s can be obtained on the basis of Le – Chatelier’s principle?
A. Dissociation constant of a weak acid
B. Entropy change in a reaction
C. Equilibrium constant of a chemical reaction
D. Shift equilibrium position on changing value of a constant.
13. The reaction  is endothermic. The forward reaction is
A. Flavoured by decrease in temperature
B. Flavoured by decrease in pressure
C. Unchanged on hanging pressure
D. equilibrium point shifts by adding catalyst
14. Consider the reaction equilibrium
kJ
On the basis of Le – Chatelier’s principle, the condition favourable for the forward reaction is
A. increasing temperature as well as pressure
B. lowering the temperature and increasing the pressure
C. any value of temperature and pressure
D. lowering of temperature as well as pressure
15. The yield of  in the reaction
kcal is affected by
A. Change in pressure and temperature
B. Change in temperature and concentration of
C. Change in pressure and concentration of
D. Change in pressure, temperature and concentration of
C. Effect of change of concentration
i. The increase in the concentration of any of the reactants shifts the equilibrium toward forwards direction.
ii. The increase in the concentration of any of the products shifts the equilibrium towards backward direction.
D. Effect of catalyst on equilibrium
A catalyst has no effect on the equilibrium point. This is because the catalyst increases the speed of both the forward and backward reactions to the same extent. It merely. It merely helps to attain the equilibrium earlier.
E. Effect of change of volume
i. The increase in the volume shifts the equilibrium in the direction of increasing moles.
ii. The decrease in the volume shifts the equilibrium in the direction of decreasing moles.
iii. The change in volume will not have any effect on the reaction where number of moles of reactants is equal to number of moles of products.
32. The gaseous reaction
is most favoured at:
A. low temperature and high pressure
B. high temperature and high pressure
C. high temperature and low pressure
D. low temperature and low pressure
33.  reaction in a lime kiln goes to completion because
A. CaO does not react to  to give
B. Backward reaction is very slow
C.  formed escape out
D. none of these.
34. For a reaction if  the forward reaction is favoured by:
A. low pressure B. high pressure
C. high temperature D. low temperature
35. In a lime kiln, to get higher yield of , the measure that can be taken is
A. to remove CaO
B. to add more
C. to maintain high temperature
D. to pump out
36. In a reversible reaction, the catalyst
A. increase the activation energy of the backward reaction.
B. increase the activation energy of the forward reaction
C. decrease the activation energy of both, forward and backward reaction.
D. decreases the activation energy of forward reaction.
16. ELECTOLYTE
A substance which either in molten state or in aqueous solution conduct electricity is known as electrolyte.
Types of electrolytes
A. Strong electrolytes
The electrolyte which are almost completely ionized are called strong electrolytes.
For example:  etc.

B. Weak electrolytes
The electrolytes which are ionised to smaller extent are known as weak electrolytes.
For example:  etc.
Expressing the strength of electrolyte
Strength of an electrolyte is expressed in terms of degree of ionisation ().
Number of molecules of the
Degree of ionisation,
Dissociation
Separation of ions from ionic compound.
Ionisation
Separation of ions when neutral polar molecule dissolved in water.
Red Alert
For strong electrolyte,  is almost equal to 1. For weak electrolyte,  has a value smaller than 1.
17. OSTWALD’S DILUTION LAW
In case of a weak electrolyte at a given temperature, the degree of ionisations is inversely proportional to the square root of the molar concentration or directly proportional to square root of the volume of the solution which contains one mole of the electrolyte.
Misconcepts
The misconcept is that this law is applicable to all type of electrolytes. The concept is that it is applicable only to weak electrolytes.
For weak electrolytes

And
Where K is known as ionisation constant.
Red Alert
For weak acids :
And
For weak bases;
and
Check Your Grasp
37. Ostwald’s dilution law is applicable to
A. strong electrolytes only
B. Weak electrolytes only
C. non-electrolytes
D. strong as well as weak electrolytes.
38. % ionistion of a weak acid can be calculated using the formula
A. B.
C. both correct D. none is correct
39. Theory of ionization was given by
A. Faraday B. Rutherford
C. Arrhenius D. Graham
40. The degree of ionization of a substance
A. decreases with dilution
B. increases with dilution
C. may increase or decrease with dilution
D. is not affected with dilution.
18. THEORIES OF ACIDS AND BASES
Acid : An acid is a substance with sour taste. It turns blue litmus red. It liberates hydrogen with active metal like sodium, calcium, magnesium etc.
Aqueous solution of an acid is characterized by  or  ions.
Base : A base is a substance with bitter taste. It turns red litmus blue. It has a soapy touch.
Aqueous solution of a base is characterized by  ions.
Three theories have been given to explain acidic and basic characters of the substances. These are:
A. Arrhenius concept of acids and bases
According to Arrhenius concept of acids and bases, an acid is a substance which gives  ions in the aqueous solution whereas a base is a substance which gives  ions in the aqueous solution.
i. The relative strengths of weak acids and weak bases are generally compared in terms of their dissociation constants
as : For weak acids:

For weak bases:
Where , ,  and  are dissociation constants for acids , , and bases ,  respectively. ,  are the degree of dissociation for acids and bases respectively.
Red Alert
ii. Arrhenius theory is valid for aqueous solutions only.
iii. Arrhenius theory does not account for the basicity of substances like, ammonia which do not possess a hydroxyl group.
iv. Expressing  for weak acids

B. Bronsted Lowry concept of acids and bases
According to Bronste-Lowry concept of acids and bases, an acid is a substance which can lose a proton and a base is a substance which can accepts a proton.
i. Conjugate acid-base pair: An acid-base pair which differs by a proton is called conjugate acid-base pair. Conjugate acid  Conjugate base + .


ii. Amphoteric substance: A substance which can act both as an acid as well as base in different reactions is called amphoteric substance. Water has dual role. In case of reaction with HCl water acts as a base while in case of ammonia it acts as an acid by donating a proton. Bronsted Lowry concept is applicable to both aqueous as well as non aqueous solutions.
Red Alert
Comparison of relative strength of acids and bases.
i. A strong acid has a weak conjugate base and vice versa. Similary, a strong base has a weak conjugate acid and vice versa. For example : Increasing order of acidic strength is . is the strongest acid and  is a weakest acid. Order of strength of their respective conjugate bases is
hence  is the strongest base.
ii. A base in contact with a strong acid behaves as a strong base while a base in contact with a weak acid behaves as a weak base.
Note
Comparison of Bronsted-Lowry and Arrhenius concepts
i. All Arrhenius acids are Bronsted acids.
ii. All Arrhenius bases are not Bronsted bases.
C. Lewis concept of acids and bases
According to Lewis concept of acids and bases, an acid is a substance which can accept a pair of electrons whereas a base is a substance which can donate a pair of electrons.
i. Types of Lewis bases
1. Neutral molecules containing a lone pair of electrons on the central atom like  , ,  etc.
2. All negative ions like , , , , , etc.
ii. Types of Lewis acids
1. Molecules having central atom with incomplete octet For example: ,  etc.
2. Simple cations. For example : , , etc.
3. Molecules having central atom with empty - orbitals for example: , , ,  etc.
4. Molecules containing multiple bonds between different atoms. For example:
? EXCEPTIONS
 is a strong acid but it can even act as a base. This is possible, when  is mixed with another acid which is stronger than it.
Misconcepts
The misconcept is that pH value for acid can be more than 7. The concept is for M HCl solution, pH is not 8, because acid solutions always have pH < 7. For this solution, pH=6.96.
F. For weak acid/base, the pH shall depend on its degree of ionisation. For example, pH of weak acid HA is given as

equivalent conc.  C


Also since  of weak acid

Hene
EXAMPLE
EXAMPLE:2 100 mL of 0.01 N HCl is mixed with 400 mL of 0.02N  solutions at . The pH of resulting solution is
A. 2.73 B. 3
C. 0 D. 4.1




SOLUTION: Resulting normality





Check Your Grasp
51. An aqueous solution whose pH=1.2 is
A. acidic B. neutral
C. basic D. amphoteric
52. The pH of pure water at  is close to
A. 0 B. 7
C. 2 D. 9
53. pH of a solution is defined by the expression
A. log   B.
C. D.
54. The term pH comes from
A. pure hydrogen content.
B. “pure voir hydrogen ’’ which implies potential of hydrogen.
C. purity of hydrogen ions in solution.
D. name of the scientist associated.
55. A pH of signifies
A. pure water B. neural solution
C. basic solution D. acidic solution
56. For a solution at 298 K, the sum of pH and pOH will be equal to
A. zero
B. B. fourteen
C. a negative number
D. infinity



23. COMMON ION EFFECT
When in a solution of acetic acid (weak electrolyte), sodium acetate (a strong electrolyte) having same common ion  is added, it results in the decrease in ionization of acetic acid according to Le- Chatelier’s principle and pH increases. This is called
Common ion effect.


Similarly, addition of  to a solution of  (weak electrolyte) results in the decreases in dissociation of .Thus, common ion effect is defined as,
“the suppression of the dissociation of a weak electrolyte by the addition of a strong electrolyte having same common ion”.
24. ACID BASE NEUTRALISATION (FORMATION OF SALT)
Acid + base
Different types of solutions are formed during acid base neutralisation depending upon the nature of acid and base.
A. A solution of strong acid and strong base is neutral.
B. A solution of strong acid and weak base is acidic.
C. A solution of weak acid and strong base is basic.
D. A solution of weak acid and weak base may be acidic, basic or neutral depending upon their relative strength.
TRICK
Nature of solution is governed by the strong component.
Type of salts
A. Acidic salts
Salts formed by the incomplete neutralisation of polyprotic acide which still contain some acidic hydrogen are called acidic salts.
For example: , , , , etc.
B. Basic salts
Salts formed by incomplete neutralisation of poly acidic bases which still contain one or more hydroxyl groups.
For example:
C. Mixed salts give more than one anions or cations on dissolving in water. For example:  gives and .
Red Alert
When a salt is dissolved in water to produce ions, the process is always endothermic since energy is required to break salt into ions.
Check Your Grasp
57. When  is added to a solution of-
A. only the concentration of ions increases
B. only the concentration of  ions decreases
C. the concentration of  ions decreases
D. the concentration of  as well as  ions decreases.


58. Which one of the following is acid salt?
A. B.
C. D.
59. Which one is not an acid salt?
A. B.
C. NaCl D. Both (a) and (b)
60. Neutralization of an acid with a base, invariably results in the production of
A. B.
C.  and D.
26. ROLE OF INCDICATOR IN ACID-BASE TITRATION (VOLUMETRIC ANALYSIS)
An indicator is a substance which is used to determine the end point in a titration. pH indicators are either weak acids or weak bases.
Two theories have been proposed to explain the change of colour of indicators.
A. Ostwald’s theory
According to this theory the colour change is due to ionisation of the acid-base indicator. The unionised form has different colour than the ionised form.
B. Quinonoid theory
According to this theory the acid-base indicators exist in two tautomeric forms having different structures benzenoid form and quinonoid form. These two forms have different colours.
Note
Sr.No. Indicator pH range Colour change
1. Methyl orange Pink to yellow
2. Methyl red Red to yellow
3. Red litmus Red to blue
4. Phenol red Yellow to Red
5. Phenolphthalein Colourless to pink
The colour change and the pH range of some common indicators

Red Alert
The suitable indicators of the following titrations are
A. Strong acid versus strong base – Phenolphthalein,                                                                              
methyl red and
methyl orange
B. Weak acid versus strong base – Phenolphthalein
C. Strong acid versus weak base – Methyl red and methyl orange. - Methyl red and
methyl orange.
D. Weak acid versus weak base – No suitable indicator.
E. During titration with  no indicator is used because  is a self indicator.
Check Your Grasp
61. The pH indicators are
A. salt of strong acids and strong bases
B. salts of weak acids and weak bases
C. either weak acids or weak bases
D. either strong acids or strong bases.


62. Identify the indicator used to litrate  solution with
A. phenolphthalein B. dilute
C. methyl orange D. none
26. SALT HYDROLYSIS
Hydrolysis is a process in which a salt reacts with water to form acid and base.
Salt + water  acid + base
Salt hydrolysis is reverse of neutralisation reaction.
Types of salt hydrolysis
There are four cases of salt hydrolysis. These are as follows:
A. Hydrolysis of salts of strong acids and strong bases
i. Examples of these salts are , , , , ,  etc.



ii. since , the resulting solution is neutral and its pH is 7.
Red Alert
iiii. Salts of strong acids and strong bases do not undergo hydrolysis. They simply forms ions in the solution
EXAMPLE
EXAMPLE:3 Mark the incorrect statement regarding  solution
A. Solution can act as a buffer solution
B. For the solution,
C. Solution involves only anionic hydrolysis
D. Degree of hydrolysis is equal to
Solution salt of a weak base an a week acid. It involves cationic as well as anionic hydrolysis.
Check Your Grasp
70. An acidic buffer solution can be prepared by mixing equimolar amounts of
A. formic acid and sodium formate
B.  and
C.  and
D.  and KOH
71. What is incorrect about buffer solution?
A. It contains a weak acid and its conjugate base
B. It contains a weak base and its conjugate acid
C. It shows change in pH on adding small amount of acid or base
D. All of the above.
29. SOLUBILITY EQUILIBRIA
Solubility equilibria for a particular salt is represented by the saturated solution of the salt at a given temperature. The state of equilibrium exists between the salt present at the bottom of the container and the ions formed in solution.

(in solution)

Solubility product constant
Solubility product of an electrolyte at a particular temperature is defined as the product of the molar concentration of its ions in a saturated solution, each concentration raised to the power equal to the number of ions produced on dissociation of one molecule of the substance i,e., for the electrolyte.


yS
At equilibrium
is known as solubility product constant.
A. A salt in solution will be precipitated at a given temperature only if the product of the ionic concentration is more than its  values. A salt with more than its   value.
B. The relative solubilities of salts in water can be compared in terms of  values. A salt with more  value is more soluble.
A
A
A is more soluble in water than AgBr.
Application of solubility product and common ion effect
i. The concept of solubility product helps in predicting the formation of a precipitate. In general,
A. If ionic product , no precipitate is formed
B. if ionic product , a precipitate is formed.
ii. In predicting the solubility of a sparingly soluble salt.
A. For AB type
S
B. For B type
S
C. For
S
D. For  type
S
Where A is cationic part and B is anionic part. And S is the solubility,  is solubility product constant.

iii. In qualitative analysis
The separation and identification of various basic radicals into different groups is based upon () solubility product principle and (b) common ion effect.
iv. Purification of common salt
saturated solution of impure common salt is prepared and insoluble impurities are filtered off.  gas is passed through this solution.
N
H
The concentration of  ions increases due to ionization of . Thus the ionic product  exceeds the solubility product and pure sodium chloride precipitates out from the solution.
V. Salting out a soap
Soaps are sodium o potassium  salts of higher fatty acids. As the solubility of soap in not much, any soap present in the solution is salted out by the addition of sodium chloride, which increase the conc. of  ions. Thus, the ionic product of   exceeds the solubility product of soap and, therefore, soap precipitates out from the solution. This is called salting out of soap.
EXAMPLE
EXAMPLE:4 If the solubility of calcium phosphate  is ‘a’ mol , the solubility product is equal to
A.   B.
C. D.
SOLUTION:

Check Your Grasp
72. Precipitation takes place when the ionic product
A. equals the solubility product
B. exceeds the solubility product
C. is less then the solubility product
D. is almost zero.
73. Which of the following is most soluble?
A.
B. MnS
C.
D.