Class 11 Chemistry - Chapter The p Block Elements NCERT Solutions | Boric acid is polymeric due to (a) it

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.

Write balanced equations for:

(i) BF₃ + LiH →

(ii) B₂H₆ + H₂O →

(iii) NaH + B₂H₆ →

(iv) H₃BO₃ 

(v) Al + NaOH →

(vi) B₂H₆ + NH₃ →

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.

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?

Why do elements in the same group have similar physical and chemical properties?

Anything that influences the valence electrons will affect the chemistry of the element. Which one of the following factors does not affect the valence shell?
(a) Valence principal quantum number (n)
(b) Nuclear charge (Z)
(c) Nuclear mass
(d) Number of core electrons.

Describe the usefulness of water in biosphere and biological systems.

The reaction:

CH₃CH₂I + KOH(aq) → CH₃CH₂OH + KI

is classified as :

(a) electrophilic substitution

(b) nucleophilic substitution

(c) elimination

(d) addition

Kp = 0.04 atm at 899 K for the equilibrium shown below. What is the equilibrium concentration of C₂H₆ when it is placed in a flask at 4.0 atm pressure and allowed to come to equilibrium?

C₂H₆ (g) ↔ C₂H₄ (g) + H₂ (g)

Draw formulas for the first five members of each homologous series beginning with the following compounds.

(a) H-COOH

(b) CH₃COCH₃

(c) H-CH=CH₂

Describe the importance of the following: (i) limestone (ii) cement (iii) plaster of paris.

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)

Define octet rule. Write its significance and limitations.

Enthalpy of combustion of carbon to CO₂ is -393.5 kJ mol^-1. Calculate the heat released upon formation of 35.2 g of CO₂ from carbon and dioxygen gas.