NTSE Notes on "Acids, Bases, Salts and pH"

These are basic theories and concepts of chemistry chapter (Acids, Bases, Salts and pH) Learn And Practice For NTSE Examinations.

·   Acids => Acids are the substances          that taste sour, turn t blue litmus red      and liberate H₂ gas on reaction with      me metals.

·Bases => Bases are substances that        are bitter in taste, slippery in touch        and turn red litmus blue. Acids and bases neutralize each other.

·   Arrhenius Concept => According to Arrhenius, acids are substances that              produce hydrogen ions when mixed with water, and bases are substances that        produces that produce hydroxyl ions(OH^‑) when mixed with water.

   For example: HCI (aq) + CI ^- (aq); HCI is an acid.

   NaOH (aq)  à Na⁺ (aq) + OH^‑ (aq) ; NaOH is base.

·   Strong Acids and Strong Bases => Strong acids (or bases) dissociate                   completely and weak acids (or bases) dissociate to a smaller extent.

  Examples of  Strong acids: H₂SO₄, HNO₃, HCI, HCIO₄   

  Examples of Strong bases: KOH, NaOH, Ba(OH)₂    

  Examples of  Weak acids: CH₃ COOH, HCOOH, HF  

  Examples of  Weak bases: NH₄OH, Ca(OH)₂

·   Acid-Base Indicator  => There are many substances which show one colour in     acid medium and different  colour in basic         medium. Such substances are       known as acid-base indicator.

·   Acids Dilution => Acids are always diluted by adding acid into water and not       by adding water into acid.

·   Acids Definition Further => Later on, we have also defined acid as a substance   which donates proton (H⁺) and base is one which  accepts proton (H⁺). The           acidity or alkalinity of a solution can be expressed in terms of hydrogen ion   concentration.

 Neutral solution à  [H⁺] = 10^-7 mol/L

 Acid solution à [H⁺] > 10^-7 mol/L

· pH Scale => The pH scale was introduced by Soreness to express acidity or           basicity of a solution. The pH is defined as pH = - log₁₀ [H⁺)

  the negative logarithm of the hydrogen ion concentration in moles per liter.

  

  For, Neutral solution :    pH = 7

       Acid solution:     pH < 7

       Basic solution:    pH > 7

as H⁺ ion increases, pH decreases and as OH^- ion increases, pH increases.

·   Salts => Salts are formed when acid and base neutralize each other. Salts are         electrolytes which contain positive and negative radicals.

·   Types of Salt Formation =>

·   Salts having the same positive or negative radicals are said to belong to a family.

  Sodium salt family: NaCI, Na₂SO₄, NaNO₃

  Potassium family: KCI, KNO₃

  Chloride salts family: NaCI, KCI

  Sulphate salts family: Na₂SO_4, (NH₄)₂SO₄

·   Salts formed by the neutralization of strong acid and strong base are called as       neutral salts. Example: NaCI (sodium chloride).

·  Salts formed by the neutralization of strong acid and weak base are called as         acidic salts. Example: NH₄CI (ammonium chloride).

· Salts formed by the neutralization of weak acid and strong base are called as          basic salts. Example: CH₃COONa (sodium acetate).