Solubility and Solubility Product

The ability or property of any substance that can dissolve in a solvent is known to be solubility or in other words, solubility is the number of grams of solute in one litre of a saturated solution. The substance mentioned here can be solute and the solvent can be solid, liquid or gaseous.

Factors affecting the solubility

  1. Temperature: As the temperature increases the solubility increases
  2. Pressure
  3. Common ion effect: It reduces the solubility
  4. pH
  5. Size of solute molecules

Solubility Product

Solubility represents the dissolution of a substance whereas the solubility product is the mathematical description of the dissolved ion concentration. At a particular temperature and pressure, the solubility product will be constant. The constant is known as ‘solubility product constant’ It shows the equilibrium between the dissolved and undissolved species.

The solubility product constant is denoted as Ksp. It depends only on temperature.

Consider a simple reaction

aA ↔ bB + cC

Here B and C are dissolved products whereas A is undissolved one. Therefore the solubility product constant can be expressed as

Ksp = [B]b.[C]c

Example: BaSO4 ↔ Ba2+ + SO42-

The solubility product constant Ksp =  [Ba2+][SO42-]

Problems on solubility product

  1. The solubility of BaSO4 is 3.9*10-5 mol/L at 25℃. Calculate Ksp value of BaSO4.

Solution:

BaSO4 ↔ Ba2+ + SO42-

Ksp =  [Ba2+][SO42-]

= S x S = S2

= (3.9*10-5)(3.9*10-5)

= 1.520*10-9

Enzyme catalyst

Catalysts are those which helps in the enhancement of the reaction without itself being changed by the reaction. Enzymes are the proteins produced by living cells. The enzyme catalyzes biochemical reactions.

Enzyme catalyst increases the chemical reactions which further convert substrate into products. In an enzyme-catalyzed reaction, the substrate binds reversibly to the active site of the enzyme.

Mechanism of an Enzyme-Catalyzed Reaction

Mechanism of an Enzyme-Catalyzed Reaction
Mechanism of an Enzyme-Catalyzed Reaction

The enzyme molecule binds molecule specifically and reversibly to the substrate molecule which then converted into the products by forming and breaking the chemical bonds. The enzyme catalyst enhances the reaction

E(enzyme) + S(substrate) ↔ ES(enzyme-substrate complex)  ↔ E(enzyme) + P(product)

Characteristics of Enzyme-Catalysed reaction

  • It is efficient as the molecules involved in the catalysis can change the millions of molecules in the substrate
  • The enzyme will not be same it varies as the same cannot be used more than one reaction.
  • The enzyme can work at its optimum temperature effectively.
  • It also has an optimal pH which ranges between 5 to 7 which makes an enzyme effective.
  • Enzyme activity is increased by the coenzymes like Na+ and CO2+

Summary

  • Solubility is the number of grams of solute in one litre of a saturated solution whereas the solubility product is the mathematical description of the dissolved ion concentration
  • The solubility product constant is denoted as Ksp
  • The enzyme catalyst enhances a biochemical reaction.

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