Class 11 Chemistry - Chapter The p Block Elements NCERT Solutions | Write balanced equations for: (i) BF3

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?

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.

Write reactions to justify amphoteric nature of aluminium.

Why does boron trifluoride behave as a Lewis acid?

Discuss the pattern of variation in the oxidation states of
(i) B to Tl and (ii) C to Pb.

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

A certain salt X, gives the following results.

(i) Its aqueous solution is alkaline to litmus.

(ii) It swells up to a glassy material Yon strong heating.

(iii) When conc. H₂SO₄ is added to a hot solution of X, white crystal of an acid Z separates out.

Write equations for all the above reactions and identify X, Y and Z.

(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.

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.

An aqueous solution of borax is

(a) neutral (b) amphoteric (c) basic (d) acidic

How do you account for the formation of ethane during chlorination of methane?

What are hybridisation states of each carbon atom in the following compounds ?

(i) CH₂=C=O,

(ii) CH₃CH=CH₂,

(iii) (CH₃)₂CO,

(iv) CH₂=CHCN,

(v) C₆H₆

What will be the minimum pressure required to compress 500 dm³ of air at 1 bar to 200 dm³ at 30°C?

What are the common physical and chemical features of alkali metals?

Calculate the molecular mass of the following:
(i) H₂O
(ii) CO₂
(iii) CH₄

Assign oxidation number to the underlined elements in each of the following species:

(a) NaH₂PO₄

(b) NaHSO₄

(c) H₄P₂O₇

(d) K₂MnO₄

(e) CaO₂

(f) NaBH₄

(g) H₂S₂O₇

(h) KAl(SO₄)₂.12 H₂O

What is the basic theme of organisation in the periodic table?

Explain the formation of a chemical bond.

Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only.

A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure?

What do you mean by Biochemical Oxygen Demand (BOD)?

Write the expression for the equilibrium constant, K_c for each of the following reactions:

(i)   2NOCl (g)   ↔   2NO (g) + Cl₂ (g)

(ii)  2Cu(NO₃)₂ (s) ↔  2CuO (s) + 4NO₂ (g) + O₂ (g)

(iii) CH₃COOC₂H₅(aq) + H₂O(l) ↔  CH₃COOH (aq) + C₂H₅OH (aq)

(iv) Fe³⁺ (aq) + 3OH^– (aq) ↔  Fe(OH)₃ (s)

(v) I₂ (s) + 5F₂ ↔  2IF₅ 

How do you count for the following observations?

(a) Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.

(b) When concentrated sulphuric acid is added to an inorganic mixture containing chloride, we get colourless pungent smelling gas HCl, but if the mixture contains bromide then we get red vapour of bromine. Why?

Statues and monuments in India are affected by acid rain. How?

Distinguish between a sigma and a pi bond.

Describe the bulk preparation of dihydrogen by electrolytic method. What is the role of an electrolyte in this process?

A sample of HI_(g) is placed in flask at a pressure of 0.2 atm. At equilibrium the partial pressure of HI_(g) is 0.04 atm. What is K_p for the given equilibrium ?

2HI (g) ↔ H₂ (g) + I₂ (g)

Which of the following carbocation is most stable ?

Calculate the entropy change in surroundings when 1.00 mol of H₂O(l) is formed under standard conditions. Δ_fH⁰ = –286 kJ mol^–1.

Explain why BeH₂ molecule has a zero dipole moment although the Be–H bonds are polar.