List of top Chemistry Questions asked in CBSE CLASS XII

Write the reactions taking place at anode and cathode in a dry cell.

(i) Give a chemical test to distinguish between ethanal and propanal.

(ii) Which of the following acids is stronger and why ?

\( \mathrm{CH_2FCOOH} \) and \( \mathrm{CH_2ClCOOH} \)

(iii) Complete the given equation :

\( \mathrm{C_6H_5-C(=O)-O-C(=O)-CH_3} \xrightarrow{\mathrm{H_2O}} \)

(a) Arrange the following compounds in the decreasing order of their acidic strength :

Phenol, 4-Nitrophenol, 2,4,6-Trinitrophenol

(b) Why are alcohols more soluble in water than hydrocarbons of comparable molecular masses ?

(c) Name the reagent used in the oxidation of a primary unsaturated alcohol to an aldehyde.

(a) What happens when chlorobutane is treated with Na metal in the presence of dry ether ?

(b) Arrange the following compounds in increasing order of their boiling points :

1-Bromobutane, 1-Iodobutane, Butane, 1-Chlorobutane

A reaction is of first order with respect to A and of second order with respect to B. What will happen to the rate of reaction if (i) only the concentration of B is increased to three times, and (ii) A is taken in excess ?

Assertion (A) : Out of \( \mathrm{[Co(en)_3]^{3+}} \) and \( \mathrm{[Co(CN)_6]^{3-}} \), coordination compound \( \mathrm{[Co(en)_3]^{3+}} \) is a more stable complex.

Reason (R) : Ethane-1,2-diamine is a chelating ligand.

Assertion (A) : Phosphorus halides are preferred over thionyl chloride for the preparation of alkyl halides from alcohols.

Reason (R) : Reaction of alcohols with thionyl chloride forms pure alkyl halides.

(i) Which element in 3d series of transition elements does not exhibit variable oxidation states ? Give reason.

(ii) Explain why \( \mathrm{Cu^{+}} \) is colourless in aqueous solution, whereas \( \mathrm{Cu^{2+}} \) is coloured.

Assertion (A) : Aromatic carboxylic acids do not undergo Friedel-Crafts reaction.

Reason (R) : Carboxyl group is deactivating and the catalyst aluminium chloride gets bonded to carboxyl group.

(i) Why do Zr and Hf exhibit similar properties ?

(ii) "\( E^\circ \) for \( \mathrm{Mn^{3+}/Mn^{2+}} \) couple is more positive than that for \( \mathrm{Fe^{3+}/Fe^{2+}} \)." Justify the statement.

[Atomic number : Mn = 25, Fe = 26]

The correct order of reactivity of alcohols with Lucas reagent is :

The relationship between \( \mathrm{E^{\circ}_{(cell)}} \) and \( \Delta_r G^{\ominus} \) is :

The quantity of electricity in Faraday, required to reduce 1 mol of \( \mathrm{Cr_2O_7^{2-}} \) to \( \mathrm{Cr^{3+}} \) is :

Functional groups present in amino acids are :

Assertion (A) : The volume of an ideal solution is equal to the sum of the volumes of the two components, i.e., \( \Delta_{mix}V = 0 \).

Reason (R) : The intermolecular forces of attraction between the solute-solvent molecules are weaker than those between the solute-solute and solvent-solvent molecules.

Which of the following statements is true about a galvanic cell consisting of Cu and \( \mathrm{H_2} \) electrodes ?

[Given : \( \mathrm{E^{\circ}_{Cu^{2+}/Cu}} = +0.34\ \mathrm{V} \), \( \mathrm{E^{\circ}_{H^+/H_2,\,Pt}} = +0.00\ \mathrm{V} \)]

The products of the following reaction are :

\( \mathrm{C_6H_5CH_2OC_6H_5} \xrightarrow{\mathrm{HI}} \)

(i) \( \mathrm{C_6H_5CH_2I} \)

(ii) \( \mathrm{C_6H_5OH} \)

(iii) \( \mathrm{C_6H_5OCH_3} \)

A galvanic cell functions like an electrolytic cell when :

According to Alfred Werner, the secondary valence(s) of the central metal atom/ion in a complex :

Identify the incorrect statement from the statements given in the options.

Match Column I with Column II and choose the correct option :

Phenol, on heating with conc. \( \mathrm{HNO_3} \), gives :

Which of the following elements exhibits maximum number of oxidation states ?

Which of the following reactions is used for the preparation of Aniline ?