Science (English Medium) Class 11 - CBSE Question Bank Solutions

Calculate the amount of carbon dioxide that could be produced when 2 moles of carbon are burnt in 16 g of dioxygen.

What is the concentration of sugar (C₁₂H₂₂O₁₁) in mol L^–1 if its 20 g are dissolved in enough water to make a final volume up to 2 L?

If the density of methanol is 0.793 kg L^–1, what is its volume needed for making 2.5 L of its 0.25 M solution?

A sample of drinking water was found to be severely contaminated with chloroform, CHCl₃, supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass).

1. Express this in percent by mass.
2. Determine the molality of chloroform in the water sample.

Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation:

\[\ce{N2 (g) + 3H2 (g) → 2NH3 (g)}\]

(i) Calculate the mass of ammonia produced if 2.00 × 10³ g dinitrogen reacts with 1.00 × 10³ g of dihydrogen.

(ii) Will any of the two reactants remain unreacted?

(iii) If yes, which one and what would be its mass?

Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040 (assume the density of water to be one).

An electron is in one of the 3d orbitals. Give the possible values of n, l and m_l for this electron.

The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus?

What is meant by hybridisation of atomic orbitals?

Describe the shapes of sp, sp²,sp³ hybrid orbitals.

Describe the change in hybridisation (if any) of the Al atom in the following reaction.

\[\ce{AlCl_3 + Cl- -> AlCl_4-}\]

Is there any change in the hybridisation of B and N atoms as a result of the following reaction?

\[\ce{BF3 + NH3 → F3B.NH3}\]

Considering x-axis as the internuclear axis which out of the following will not form a sigma bond and why?

1. 1s and 1s
2. 1s and 2px
3. 2py and 2py
4. 1s and 2s.

Which hybrid orbitals are used by carbon atoms in the following molecules?

CH₃–CH₃

For the reaction at 298 K,

\[\ce{2A + B → C}\]

ΔH = 400 kJ mol^-1 and ΔS = 0.2 kJ K^-1 mol^-1

At what temperature will the reaction become spontaneous considering ΔH and ΔS to be constant over the temperature range?

For the reaction

\[\ce{2A_{(g)} + B_{(g)} → 2D_{(g)}}\]

ΔU^θ = –10.5 kJ and ΔS^θ= –44.1 JK^–1.

Calculate ΔG^θ for the reaction, and predict whether the reaction may occur spontaneously.

Why is benzene extra ordinarily stable though it contains three double bonds?

Write down the products of ozonolysis of 1, 2-dimethylbenzene (o-xylene). How does the result support Kekulé structure for benzene?

Give a brief description of the principle of the following technique taking an example.

Distillation 

What is the difference between distillation, distillation under reduced pressure and steam distillation ?