List of top Chemistry Questions asked in CBSE Class XI

The reaction, \(CO(g) + 3H_2(g) \leftrightarrow CH_4(g) + H_2O(g)\) is at equilibrium at 1300 K in a 1L flask. It also contain 0.30 mol of CO, 0.10 mol of \(H_2\) and 0.02 mol of \(H_2O\) and an unknown amount of \(CH_4\) in the flask. Determine the concentration of \(CH_4\) in the mixture. The equilibrium constant, \(K_c\) for the reaction at the given temperature is 3.90.

Why is a solution of potassium hydroxide used to absorb carbon dioxide evolved during the estimation of carbon present in an organic compound?

The value of \(K_c\) for the reaction  \(3O_2 \,(g) \leftrightarrow 2O_3 \,(g)\) is \(2.0 ×10^{–50}\) at 25°C. If the equilibrium concentration of \(O_2\) in air at 25°C is \(1.6 ×10^{–2}\), what is the concentration of \(O_3\)?

What are hybridization states of each carbon atom in the following compounds? 
\(CH_2=C=O,\, CH_3CH=CH_2\),\((CH_3)_2CO, \,CH_2=CHCN, \,C_6H_6.\)

Will CCl₄ give white precipitate of AgCl on heating it with silver nitrate? Give reason for your answer.

Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation ?

Name a suitable technique of separation of the components from a mixture of calcium sulphate and camphor.

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

Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen, sulphur and halogens.

Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?

Write Lewis symbols for the following atoms and ions: \(S\) and \(S ^{2-}\) ; \(Al\) and \(Al ^{3+}\) ; \(H\) and \(H ^-\)

Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.

The following data are obtained when dinitrogen and dioxygen react together to form different compounds: 
          Mass of dinitrogen                Mass of dioxygen 
(i)              14 g                                            16 g 
(ii)             14 g                                             32 g 
(iii)            28 g                                             32 g 
(iv)            28 g                                             80 g 

1. Which law of chemical combination is obeyed by the above experimental data? Give its statement.
2. Fill in the blanks in the following conversions: 
   (i)1 km = ...................... mm = ...................... pm 
   (ii) 1 mg = ...................... kg = ...................... ng 
   (iii) 1 mL = ...................... L = ...................... dm³

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 per cent by mass.
2. Determine the molality of chloroform in the water sample.

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 2L?

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

Describe the method, which can be used to separate two compounds with different solubilities in a solvent S.

Identify the reagents shown in bold in the following equations as nucleophiles or electrophiles. 
(a) \(CH_3COOH+HO^{–6} \rightarrow CH_3COO^–+H_2O\) 
(b) \(CH_3COCH^{3+} C^–N\rightarrow (CH_3)_2C(CN)(OH)\)
(c) \(C_6H_6 + CH_3C+O^+ \rightarrow C_6H_5COCH_3\)

Calculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41 g mL^–1 and the mass per cent of nitric acid in it being 69%.

What are electrophiles and nucleophiles? Explain with examples.

Which of the two, \(O+2NCH_2CH_2O^- \,or \,CH_3CH_2O^–\)is expected to be more stable and why?

Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wavenumber (v) of the yellow light

Give the IUPAC names of the following compounds:

(f) Cl₂CHCH₂OH

An ion with mass number 37 possesses one unit of negative charge. If the ion conatins 11.1% more neutrons than the electrons, find the symbol of the ion.

Calculate the oxidation number of Sulphur, chromium, and nitrogen in
\(H_2SO_5\), \(Cr_2O_7^{2−}\) and \(NO_3^−\). Suggest structure of these compounds. Count for the fallacy.