SoluBility ncert
Content
Solubility Solubility of a substance is its maximum amount that can be dissolved in a specified amount of solvent at a specified temperature concentration of solute in such a solution is its solubility.
depends on a number of factors important amongst which are the lattice enthalpy of the salt and the solvation enthalpy of the ions in a solution if in a nearly saturated solution, the dissolution process is endothermic (sol H > 0), the solubility should increase with rise in temperature and if it is exothermic (sol H < 0) the solubility should decrease. As dissolution is an exothermic process, the solubility should decrease with increase of temperature
Soluble Solubility > 0.1M Slightly 0.01M<Solubility< 0.1M Soluble Sparingly Solubility < 0.01M Soluble
The solubility of a solid in a liquid is significantly affected by temperature Changes Solubility of gases in liquids decreases with rise in temperature. the solubility of most salts in water increases with rise of temperature. The solubility of gases increase with increase of pressure The solubility of the gas will increase until a new equilibrium is reached resulting in an increase in the pressure of a gas above the solution and thus its solubility increases. higher the value of KH at a given pressure, the lower is the solubility of the gas in the liquid (in henry law ) Scuba divers must cope with high concentrations of dissolved gases while breathing air at high pressure underwater. Increased pressure increases the solubility of atmospheric gases in blood. When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries and creates a medical condition known as bends, which are painful and dangerous to life. To avoid bends, as well as, the toxic effects of high concentrations of nitrogen in the blood, the tanks used by scuba divers are filled with air diluted with helium (11.7% helium, 56.2% nitrogen and 32.1% oxygen For most of the ionic compounds, sol H0 is positive and the dissociation process is endothermic. Therefore the solubility of most salts in water increases with rise of temperature We shall now consider the equilibrium
between the sparingly soluble ionic salt and its saturated aqueous solution equation: K = {[Ba2+][SO4 2–]} / [BaSO4] For a pure solid substance the concentration remains constant and we can write Ksp = K[BaSO4] = [Ba2+][SO4 2–] (7.39) We call Ksp the solubility product constant or simply solubility product The experimental value of Ksp in above equation at 298K is 1.1 10–10. This means that for solid barium sulphate in equilibrium with its saturated solution, the product of the concentrations of barium and sulphate ions is equal to its solubility product constant. zirconium phosphate of molecular formula (Zr4+)3(PO4 3–)4. It dissociates into 3 zirconium cations of charge +4 and 4 phosphate anions of charge –3. [Zr4+] = 3S and [PO4 3–] = 4S and Ksp = (3S)3 (4S)4 = 6912 (S)7 or S = {Ksp / (33 44)}1/7 = (Ksp / 6912)1/7 polymers have poor solubility Leaching is often used if the ore is soluble in some suitable solvent.
Zone refining
This method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal The solubility of salts of weak acids like phosphates increases at lower pH Ni(OH)2 is more soluble than AgCN. The fluorides are relatively less soluble than the chlorides owing to their high lattice energies For dissolution of solids in liquids, the solubility is constant at a given temperature Certain water soluble organic compounds like phenolphthalein and bromothymol blue behave as weak acids and exhibit different
colours in their acid (HIn) and conjugate base (In– ) forms. calcium chloride) are so soluble that they are hygroscopic in nature and even absorb water vapour from atmosphere lithium fluoride) have so little solubility that they are commonly termed as insoluble.
Cupric sulphide has such a low solubility
During boiling, the soluble Mg(HCO3)2 is converted into insoluble Mg(OH)2 and Ca(HCO3)2 is changed to insoluble CaCO3. It is because of high solubility product of Mg(OH)2 as compared to that of MgCO3, that Mg(OH)2 is precipitated All these halides are soluble in water. The low solubility of LiF in water is due to its high lattice enthalpy whereas the low solubility of CsI is due to smaller hydration enthalpy of its two ions. Other halides of lithium are soluble in ethanol, acetone and ethylacetate; LiCl is soluble in pyridine also increased covalent character of lithium compounds which is responsible for their solubility in organic solvents LiF and Li2O are comparatively much less soluble in water than the corresponding compounds of other alkali metals Lithium and magnesium oxides and hydroxides are much less soluble and their hydroxides decompose on heating LiCl and MgCl2 are soluble in ethanol Sodium dichromate is more soluble than potassium dichromate Solvay Process low solubility of sodium hydrogencarbonate whereby it gets precipitated in the reaction of sodium chloride potassium hydrogencarbonate is too soluble
to be precipitated by the addition of ammonium hydrogencarbonate to a saturated solution of potassium chloride. Sodium carbonate is readily soluble in water Sodium hydroxide is readily soluble in water to give a strong alkaline solution Calcium and magnesium chloride, being more soluble than sodium chloride sodium chloride solubility of 36.0 g in 100 g of water at 273 K. its solubility does not increase appreciably with increase in temperature. alkaline earth metals oxides except BeO are basic in nature and react with water to form sparingly soluble hydroxides. MO + H2O M(OH) Beryllium halides are essentially covalent and soluble in organic solvents
Carbonates of alkaline earth metals are insoluble in water and can be precipitated by addition of a sodium or ammonium carbonate solution to a solution of a soluble salt of these metals. BeSO4, and MgSO4 are readily soluble in water The greater hydration enthalpies of Be2+ and Mg2+ ions overcome the lattice enthalpy factor and therefore their sulphates are soluble in water. Among alkaline earth metal hydroxides, the anion being common the cationic radius will influence the lattice enthalpy. Since lattice enthalpy decreases much more than the hydration enthalpy with increasing ionic size, the solubility increases as we go down the group. The size of anions being much larger compared to cations, the lattice enthalpy will remain almost constant within a particular group. Since the hydration enthalpies decrease down the group, solubility will decrease as found for alkaline earth metal carbonates and sulphates The chlorides of both beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the
chlorides are soluble in organic solvents and are strong Lewis acids. Calcium hydroxide is sparingly soluble in water water soluble calcium hydrogencarbonate. Calcium carbonate is almost insoluble in water
hydroxides and carbonates of sodium and potassium are easily soluble in water while the corresponding salts of magnesium and calcium are sparingly soluble in water LiF almost insoluble in water whereas LiCl soluble not only in water but also in aceton BeO is almost insoluble but BeSO4 is soluble in water, (ii) BaO is soluble but BaSO4 is insoluble in water,
LiI is more soluble than KI in ethanol.
Orthoboric acid, H3BO3 is sparingly soluble in water but highly soluble in hot water. Carbon monoxide almost water insoluble gas low Carbon dioxide solubility in water With water, it forms carbonic acid, H2CO3 which is a weak dibasic acid
Aluminium trifluoride is insoluble in anhydrous HF but dissolves on addition of NaF. Aluminium trifluoride precipitates out of the resulting solution when gaseous BF3 is bubbled through
hydrogen chloride gas (HCl) is highly soluble in water Nitrogen has a very low solubility in water (23.2 cm3 per litre of water at 273 K and 1 bar pressure) Ammonia gas is highly soluble in water. Its aqueous solution is weakly basic due to the formation of OH– ions. NH3(g) + H2O(l) l NH4 + (aq) + OH– (aq) White phosphorus insoluble in water but soluble in carbon disulphide It dissolves in boiling NaOH solution in an inert atmosphere giving PH3. Red phosphorus
insoluble in water as well as in carbon disulphide
Phosphine is slightly soluble in water. Dioxygen is solubility in water
Rhombic sulphur
is insoluble in water but dissolves to some extent in benzene, alcohol and ether. It is readily soluble in CS
Monoclinic sulphur (-sulphur)
is soluble in CS2 Sulphur dioxide is soluble in water.
insoluble fluorides (fluorspar CaF2, cryolite Na3AlF6 and fluoroapatite 3Ca3(PO4)2.CaF2) Fluorine and chlorine react with water. Bromine and iodine are only sparingly soluble in water but are soluble in various organic solvents such as chloroform, carbon tetrachloride, carbon disulphide and hydrocarbons to give coloured solutions iodine oxides, I2O4 , I2O5, I2O7 are insoluble solids Chlorine is soluble in water. All the noble gases are sparingly soluble in water Potassium permanganate is not very soluble in water The haloalkanes are only very slightly soluble in water chemical stability of DDT and its fat solubility compounded the problem Solubility of alcohols and phenols in water is due to their ability to form hydrogen bonds with water molecules Alcohols are soluble in Lucas reagent (conc. HCl and ZnCl2) while their halides are immiscible and produce turbidity in solution The solubility decreases with increase in size of alkyl/aryl (hydrophobic) group of akyl hallide
the solubility of aldehydes and ketones decreases rapidly on increasing the length of alkyl chain The solubility of corboxallic acid decreases with increasing number of carbon atoms All aldehydes and ketones are fairly soluble in organic solvents like benzene, ether, methanol, chloroform, etc. The hydrogensulphite addition compound is water soluble
Benzoic acid, the simplest aromatic carboxylic acid is nearly insoluble in cold water. Carboxylic acids are also soluble in less polar organic solvents like benzene, ether, alcohol, chloroform, etc. Lower aliphatic amines are soluble in water because they can form hydrogen bonds with water molecules. However, solubility decreases with increase in molar mass of amines due to increase in size of the hydrophobic alkyl part Higher amines are essentially insoluble in water. Amines are soluble in organic solvents like alcohol, ether and benzene. Amine salts are soluble in water but insoluble in organic solvents like ether. alcohols are more polar than amines and form stronger intermolecular hydrogen bonds than amines Benzenesulphonyl chloride (C6H5SO2Cl), it is soluble in alkali N, N-diethylbenzene sulphonamide does not contain any hydrogen atom attached to nitrogen atom, it is not acidic and hence insoluble in alkali. Benzenediazonium chloride is readily soluble in water and is stable in cold but reacts with water when warmed Benzenediazonium fluoroborate is water insoluble Amylose is water soluble Amylopectin is insoluble in water Globular proteins are usually soluble in water. Insulin and albumins are the common examples of globular proteins. Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds) are insoluble in water
Amino acids are
water-soluble proteins are generally insoluble in water Fat soluble vitamins: Vitamins which are soluble in fat and oils but insoluble in water vitamins A, D, E and K. B group vitamins and vitamin C are soluble in water Water soluble vitamins must be supplied regularly in diet because they are readily excreted in urine and cannot be stored (except vitamin B12) in our body Natural rubber is soluble in non-polar solvents only treatment for acidity was administration of antacids, such as sodium hydrogencarbonate or a mixture of aluminium and magnesium hydroxide. However, excessive hydrogencarbonate can make the stomach alkaline and trigger the production of even more acid. Metal hydroxides are better alternatives because of being insoluble, these do not increase the pH above neutrality Only sodium and potassium soaps are soluble in water and are used for cleaning purposes all soaps are made by boiling fats or oils with suitable soluble hydroxide Hard water contains calcium and magnesium ions. These ions form insoluble calcium and magnesium soaps respectively when sodium or potassium soaps are dissolved in hard water. These insoluble soaps separate as scum in water and are useless as cleansing agent
depends on a number of factors important amongst which are the lattice enthalpy of the salt and the solvation enthalpy of the ions in a solution if in a nearly saturated solution, the dissolution process is endothermic (sol H > 0), the solubility should increase with rise in temperature and if it is exothermic (sol H < 0) the solubility should decrease. As dissolution is an exothermic process, the solubility should decrease with increase of temperature
Soluble Solubility > 0.1M Slightly 0.01M<Solubility< 0.1M Soluble Sparingly Solubility < 0.01M Soluble
The solubility of a solid in a liquid is significantly affected by temperature Changes Solubility of gases in liquids decreases with rise in temperature. the solubility of most salts in water increases with rise of temperature. The solubility of gases increase with increase of pressure The solubility of the gas will increase until a new equilibrium is reached resulting in an increase in the pressure of a gas above the solution and thus its solubility increases. higher the value of KH at a given pressure, the lower is the solubility of the gas in the liquid (in henry law ) Scuba divers must cope with high concentrations of dissolved gases while breathing air at high pressure underwater. Increased pressure increases the solubility of atmospheric gases in blood. When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries and creates a medical condition known as bends, which are painful and dangerous to life. To avoid bends, as well as, the toxic effects of high concentrations of nitrogen in the blood, the tanks used by scuba divers are filled with air diluted with helium (11.7% helium, 56.2% nitrogen and 32.1% oxygen For most of the ionic compounds, sol H0 is positive and the dissociation process is endothermic. Therefore the solubility of most salts in water increases with rise of temperature We shall now consider the equilibrium
between the sparingly soluble ionic salt and its saturated aqueous solution equation: K = {[Ba2+][SO4 2–]} / [BaSO4] For a pure solid substance the concentration remains constant and we can write Ksp = K[BaSO4] = [Ba2+][SO4 2–] (7.39) We call Ksp the solubility product constant or simply solubility product The experimental value of Ksp in above equation at 298K is 1.1 10–10. This means that for solid barium sulphate in equilibrium with its saturated solution, the product of the concentrations of barium and sulphate ions is equal to its solubility product constant. zirconium phosphate of molecular formula (Zr4+)3(PO4 3–)4. It dissociates into 3 zirconium cations of charge +4 and 4 phosphate anions of charge –3. [Zr4+] = 3S and [PO4 3–] = 4S and Ksp = (3S)3 (4S)4 = 6912 (S)7 or S = {Ksp / (33 44)}1/7 = (Ksp / 6912)1/7 polymers have poor solubility Leaching is often used if the ore is soluble in some suitable solvent.
Zone refining
This method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal The solubility of salts of weak acids like phosphates increases at lower pH Ni(OH)2 is more soluble than AgCN. The fluorides are relatively less soluble than the chlorides owing to their high lattice energies For dissolution of solids in liquids, the solubility is constant at a given temperature Certain water soluble organic compounds like phenolphthalein and bromothymol blue behave as weak acids and exhibit different
colours in their acid (HIn) and conjugate base (In– ) forms. calcium chloride) are so soluble that they are hygroscopic in nature and even absorb water vapour from atmosphere lithium fluoride) have so little solubility that they are commonly termed as insoluble.
Cupric sulphide has such a low solubility
During boiling, the soluble Mg(HCO3)2 is converted into insoluble Mg(OH)2 and Ca(HCO3)2 is changed to insoluble CaCO3. It is because of high solubility product of Mg(OH)2 as compared to that of MgCO3, that Mg(OH)2 is precipitated All these halides are soluble in water. The low solubility of LiF in water is due to its high lattice enthalpy whereas the low solubility of CsI is due to smaller hydration enthalpy of its two ions. Other halides of lithium are soluble in ethanol, acetone and ethylacetate; LiCl is soluble in pyridine also increased covalent character of lithium compounds which is responsible for their solubility in organic solvents LiF and Li2O are comparatively much less soluble in water than the corresponding compounds of other alkali metals Lithium and magnesium oxides and hydroxides are much less soluble and their hydroxides decompose on heating LiCl and MgCl2 are soluble in ethanol Sodium dichromate is more soluble than potassium dichromate Solvay Process low solubility of sodium hydrogencarbonate whereby it gets precipitated in the reaction of sodium chloride potassium hydrogencarbonate is too soluble
to be precipitated by the addition of ammonium hydrogencarbonate to a saturated solution of potassium chloride. Sodium carbonate is readily soluble in water Sodium hydroxide is readily soluble in water to give a strong alkaline solution Calcium and magnesium chloride, being more soluble than sodium chloride sodium chloride solubility of 36.0 g in 100 g of water at 273 K. its solubility does not increase appreciably with increase in temperature. alkaline earth metals oxides except BeO are basic in nature and react with water to form sparingly soluble hydroxides. MO + H2O M(OH) Beryllium halides are essentially covalent and soluble in organic solvents
Carbonates of alkaline earth metals are insoluble in water and can be precipitated by addition of a sodium or ammonium carbonate solution to a solution of a soluble salt of these metals. BeSO4, and MgSO4 are readily soluble in water The greater hydration enthalpies of Be2+ and Mg2+ ions overcome the lattice enthalpy factor and therefore their sulphates are soluble in water. Among alkaline earth metal hydroxides, the anion being common the cationic radius will influence the lattice enthalpy. Since lattice enthalpy decreases much more than the hydration enthalpy with increasing ionic size, the solubility increases as we go down the group. The size of anions being much larger compared to cations, the lattice enthalpy will remain almost constant within a particular group. Since the hydration enthalpies decrease down the group, solubility will decrease as found for alkaline earth metal carbonates and sulphates The chlorides of both beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the
chlorides are soluble in organic solvents and are strong Lewis acids. Calcium hydroxide is sparingly soluble in water water soluble calcium hydrogencarbonate. Calcium carbonate is almost insoluble in water
hydroxides and carbonates of sodium and potassium are easily soluble in water while the corresponding salts of magnesium and calcium are sparingly soluble in water LiF almost insoluble in water whereas LiCl soluble not only in water but also in aceton BeO is almost insoluble but BeSO4 is soluble in water, (ii) BaO is soluble but BaSO4 is insoluble in water,
LiI is more soluble than KI in ethanol.
Orthoboric acid, H3BO3 is sparingly soluble in water but highly soluble in hot water. Carbon monoxide almost water insoluble gas low Carbon dioxide solubility in water With water, it forms carbonic acid, H2CO3 which is a weak dibasic acid
Aluminium trifluoride is insoluble in anhydrous HF but dissolves on addition of NaF. Aluminium trifluoride precipitates out of the resulting solution when gaseous BF3 is bubbled through
hydrogen chloride gas (HCl) is highly soluble in water Nitrogen has a very low solubility in water (23.2 cm3 per litre of water at 273 K and 1 bar pressure) Ammonia gas is highly soluble in water. Its aqueous solution is weakly basic due to the formation of OH– ions. NH3(g) + H2O(l) l NH4 + (aq) + OH– (aq) White phosphorus insoluble in water but soluble in carbon disulphide It dissolves in boiling NaOH solution in an inert atmosphere giving PH3. Red phosphorus
insoluble in water as well as in carbon disulphide
Phosphine is slightly soluble in water. Dioxygen is solubility in water
Rhombic sulphur
is insoluble in water but dissolves to some extent in benzene, alcohol and ether. It is readily soluble in CS
Monoclinic sulphur (-sulphur)
is soluble in CS2 Sulphur dioxide is soluble in water.
insoluble fluorides (fluorspar CaF2, cryolite Na3AlF6 and fluoroapatite 3Ca3(PO4)2.CaF2) Fluorine and chlorine react with water. Bromine and iodine are only sparingly soluble in water but are soluble in various organic solvents such as chloroform, carbon tetrachloride, carbon disulphide and hydrocarbons to give coloured solutions iodine oxides, I2O4 , I2O5, I2O7 are insoluble solids Chlorine is soluble in water. All the noble gases are sparingly soluble in water Potassium permanganate is not very soluble in water The haloalkanes are only very slightly soluble in water chemical stability of DDT and its fat solubility compounded the problem Solubility of alcohols and phenols in water is due to their ability to form hydrogen bonds with water molecules Alcohols are soluble in Lucas reagent (conc. HCl and ZnCl2) while their halides are immiscible and produce turbidity in solution The solubility decreases with increase in size of alkyl/aryl (hydrophobic) group of akyl hallide
the solubility of aldehydes and ketones decreases rapidly on increasing the length of alkyl chain The solubility of corboxallic acid decreases with increasing number of carbon atoms All aldehydes and ketones are fairly soluble in organic solvents like benzene, ether, methanol, chloroform, etc. The hydrogensulphite addition compound is water soluble
Benzoic acid, the simplest aromatic carboxylic acid is nearly insoluble in cold water. Carboxylic acids are also soluble in less polar organic solvents like benzene, ether, alcohol, chloroform, etc. Lower aliphatic amines are soluble in water because they can form hydrogen bonds with water molecules. However, solubility decreases with increase in molar mass of amines due to increase in size of the hydrophobic alkyl part Higher amines are essentially insoluble in water. Amines are soluble in organic solvents like alcohol, ether and benzene. Amine salts are soluble in water but insoluble in organic solvents like ether. alcohols are more polar than amines and form stronger intermolecular hydrogen bonds than amines Benzenesulphonyl chloride (C6H5SO2Cl), it is soluble in alkali N, N-diethylbenzene sulphonamide does not contain any hydrogen atom attached to nitrogen atom, it is not acidic and hence insoluble in alkali. Benzenediazonium chloride is readily soluble in water and is stable in cold but reacts with water when warmed Benzenediazonium fluoroborate is water insoluble Amylose is water soluble Amylopectin is insoluble in water Globular proteins are usually soluble in water. Insulin and albumins are the common examples of globular proteins. Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds) are insoluble in water
Amino acids are
water-soluble proteins are generally insoluble in water Fat soluble vitamins: Vitamins which are soluble in fat and oils but insoluble in water vitamins A, D, E and K. B group vitamins and vitamin C are soluble in water Water soluble vitamins must be supplied regularly in diet because they are readily excreted in urine and cannot be stored (except vitamin B12) in our body Natural rubber is soluble in non-polar solvents only treatment for acidity was administration of antacids, such as sodium hydrogencarbonate or a mixture of aluminium and magnesium hydroxide. However, excessive hydrogencarbonate can make the stomach alkaline and trigger the production of even more acid. Metal hydroxides are better alternatives because of being insoluble, these do not increase the pH above neutrality Only sodium and potassium soaps are soluble in water and are used for cleaning purposes all soaps are made by boiling fats or oils with suitable soluble hydroxide Hard water contains calcium and magnesium ions. These ions form insoluble calcium and magnesium soaps respectively when sodium or potassium soaps are dissolved in hard water. These insoluble soaps separate as scum in water and are useless as cleansing agent
