Class 11 Chemistry - Chapter The p Block Elements NCERT Solutions | Explain what happens when boric acid is

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?

Pressure is determined as force per unit area of the surface. The SI unit of pressure, Pascal is as shown below:

1Pa = 1N m^–2

If mass of air at sea level is 1034 g cm^–2, calculate the pressure in Pascal.

Consider the reaction of water with F₂ and suggest, in terms of oxidation and reduction, which species are oxidised or reduced.

A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Calculate

(i) empirical formula,

(ii) molar mass of the gas, and

(iii) molecular formula.

Carbon monoxide gas is more dangerous than carbon dioxide gas. Why?

In Milikan’s experiment, static electric charge on the oil drops has been obtained by shining X-rays.

If the static electric charge on the oil drop is –1.282 × 10^–18C, calculate the number of electrons present on it.

An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.

Why is it necessary to use acetic acid and not sulphuric acid for acidification of sodium extract for testing sulphur by lead acetate test?

Explain the formation of H₂ molecule on the basis of valence bond theory.

At 0°C, the density of a certain oxide of a gas at 2 bar is same as that of dinitrogen at 5 bar. What is the molecular mass of the oxide?

What do you mean by green chemistry? How will it help decrease environmental pollution?