Class 11th

5.34. The temperature at which the vapour pressure of a liquid is equal to external pressure is called boiling point of liquid.

5.33. Molecules of liquids are held together byattractive intermolecular forces. Liquids havedefinite volume because molecules do notseparate from each other. However, moleculesof liquids can move past one another freely, therefore, liquids can flow, can be poured andcan assume the shape of the container in whichthese are stored.

(a) Phosphorous, chlorine and sulphur are the non metals which can show disproportionation reaction. The reactions shown are:

P_4? + 3OH^? + 3H₂? O? PH₃? + 3H₂? PO₂^?

? Cl₂? + 2OH^? ? Cl^? + ClO^? + H₂? O

S₈? +12OH^? ?4S^2? +2S₂? O₃^2? ? +6H₂? O

(b) Copper, gallium and indium are the metals that show disproportionation reaction. 

The reactions are shown below.

2Cu⁺? Cu²⁺ + Cu

3Ga⁺? Ga³⁺ + 2Ga

3In⁺? In³⁺ + 2In

5.32.  (c) F₂

5.31.  (b) frictional resistance

5.30.  (a) decreases

The balanced chemical reaction for the redox reaction between chlorine and sulphur dioxide is:

Cl₂? + SO₂? + 2H₂? O → 2Cl⁻ + SO₄²⁻ ? + 4H⁺.

5.29.  (b) increases by three times

The unbalanced chemical reaction is:
Mn³⁺ (aq) → Mn²⁺ (aq) + MnO₂? (s) + H⁺ (aq)
The oxidation half reaction is,  
Mn³⁺ (aq) → MnO₂? (s).
To balance oxidation number, one electron is added on R.H.S.
Mn³⁺ (aq) → MnO₂? (s) + e⁻
4 protons are added to balance the charge.
Mn³⁺ (aq) → MnO₂? (s) + 4H⁺ (aq) + e⁻
2 water molecules are added to balance O atoms.
The reduction half reaction is Mn³⁺ (aq) → Mn²⁺ (aq).
An electron is added to balance oxidation number.
Mn³⁺ (aq) + e⁻ → Mn²⁺ (aq)
Two half-cell reactions are added to obtain balanced chemical equation.
2Mn³⁺ (aq) + 2H₂? O (l) → Mn2+ (aq) + MnO₂? (s) + 4H⁺ (aq)