Question 2
How can you explain higher stability of BCl₃ as compared to TlCl₃?

Question 3
Why does boron trifluoride behave as a Lewis acid?

Question 4
Consider the compounds, BCl₃ and CCl₄. How will they behave with water? Justify.

Question 5
Is boric acid a protic acid? Explain.

Question 9
What are electron deficient compounds? Are BCl₃ and SiCl₄ electron deficient species? Explain.

Question 11
What is the state of hybridisation of carbon in
(a) CO^2-₃
(b) diamond
(c) graphite?

Question 13
Rationalise the given statements and give chemical reactions :
(i) Lead(II) chloride reacts with Cl₂ to give PbCl₄.
(ii) Lead(IV) chloride is highly unstable towards heat.
(iii) Lead is known not to form an iodide, PbI₄.

Question 18
How is excessive content of CO₂ responsible for global warming?

Question 20
What happens when
(a) Borax is heated strongly,
(b) Boric acid is added to water,
(c) Aluminium is treated with dilute NaOH,
(d) BF₃ is reacted with ammonia?

Question 21
Explain the following reactions
(a) Silicon is heated with methyl chloride at high temperature in the presence of copper;
(b) Silicon dioxide is treated with hydrogen fluoride;
(c) CO is heated with ZnO;
(d) Hydrated alumina is treated with aqueous NaOH solution

Question 22
Give reasons:
(i) Conc. HNO₃ can be transported in aluminium container.
(ii) A mixture of dilute NaOH and aluminium pieces is used to open drain.
(iii) Graphite is used as lubricant.
(iv) Diamond is used as an abrasive.
(v) Aluminium alloys are used to make aircraft body.
(vi) Aluminium utensils should not be kept in water overnight.
(vii) Aluminium wire is used to make transmission cables.

Question 23
Explain why is there a phenomenal decrease in ionisation enthalpy from carbon to silicon?

Question 24
How would you explain the lower atomic radius of Ga as compared to Al?

Question 25
What are allotropes? Sketch the structure of two allotropes of carbon namely diamond and graphite. What is the impact of structure on physical properties of two allotropes?

Question 26
(a) Classify following oxides as neutral, acidic, basic or amphoteric:
CO, B₂O₃, SiO₂, CO2, Al₂O₃, PbO₂, Tl₂O₃
(b) Write suitable chemical equations to show their nature.

Question 29
What do you understand by
(a) inert pair effect
(b) allotropy and
(c) catenation?

Question 31
Write balanced equations for:
(i) BF₃ + LiH →
(ii) B₂H₆ + H₂O →
(iii) NaH + B₂H₆ →
(iv) H₃BO₃  
(v) Al + NaOH →
(vi) B₂H₆ + NH₃ →

Question 33
An aqueous solution of borax is
(a) neutral (b) amphoteric (c) basic (d) acidic

Question 34
Boric acid is polymeric due to
(a) its acidic nature (b) the presence of hydrogen bonds (c) its monobasic nature (d) its geometry

Question 35
The type of hybridisation of boron in diborane is
(a) sp    (b) sp²   (c) sp³    (d) dsp²

Question 36
Thermodynamically the most stable form of carbon is
(a) diamond (b) graphite (c) fullerenes (d) coal

Question 37
Elements of group 14
(a) exhibit oxidation state of +4 only
(b) exhibit oxidation state of +2 and +4
(c) form M^2-and M⁴⁺ion
(d) form M²⁺and M⁴⁺ions