Science (English Medium) कक्षा ११ - CBSE Question Bank Solutions

Give reasons: Aluminium alloys are used to make aircraft body.

Give reasons: Aluminium utensils should not be kept in water overnight.

Give reasons: Aluminium wire is used to make transmission cables.

When metal X is treated with sodium hydroxide, a white precipitate (A) is obtained, which is soluble in excess of NaOH to give soluble complex (B). Compound (A) is soluble in dilute HCl to form compound (C). The compound (A) when heated strongly gives (D), which is used to extract the metal. Identify (X), (A), (B), (C) and (D). Write suitable equations to support their identities.

The type of hybridisation of boron in diborane is ______.

Explain the significance of sodium, potassium, magnesium and calcium in biological fluids.

State as to why sodium is found to be more useful than potassium?

Saline hydrides are known to react with water violently producing fire. Can CO₂, a well-known fire extinguisher, be used in this case? Explain.

Arrange the following:

NaH, MgH₂ and H₂O in order of increasing reducing property.

How can saline hydrides remove traces of water from organic compounds?

What do you expect the nature of hydrides is, if formed by elements of atomic numbers 15, 19, 23 and 44 with dihydrogen? Compare their behaviour towards the water.

Justify that the following reaction is redox reaction:

\[\ce{CuO(s) + H2(g) → Cu(s) + H2O(g)}\]

Justify that the following reaction is redox reaction:

\[\ce{Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)}\]

Justify that the following reaction is redox reaction:

\[\ce{4BCl3(g) + 3LiAlH4(s) → 2B2H6(g) + 3LiCl(s) + 3 AlCl3(s)}\]

Justify that the following reaction is redox reaction:

\[\ce{2K(s) + F2(g) → 2K+F– (s)}\]

Justify that the following reaction is redox reaction:

\[\ce{4 NH3(g) + 5 O2(g) → 4NO(g) + 6H2O(g)}\]

Fluorine reacts with ice and results in the change: \[\ce{H2O(s) + F2(g) → HF(g) + HOF(g)}\]

Justify that this reaction is a redox reaction.

Suggest a list of the substances where carbon can exhibit oxidation states from –4 to +4 and nitrogen from –3 to +5.

While sulphur dioxide and hydrogen peroxide can act as oxidising as well as reducing agents in their reactions, ozone and nitric acid act only as oxidants. Why?

How do you count for the following observations?

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?