Chemistry MCQs for NEET — Practice Questions with Answers

The NCERT defines Wurtz-Fittig reaction as: 'A mixture of an alkyl halide and aryl halide gives an alkylarene when treated with sodium in dry ether and is called Wurtz-Fittig reaction.'

The NCERT states, 'Aryl halides also give analogous compounds when treated with sodium in dry ether, in which two aryl groups are joined together. It is called Fittig reaction.'

The NCERT highlights this: 'Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons. It is therefore necessary to avoid even traces of moisture from a Grignard reagent.'

The NCERT defines organometallic compounds as 'compounds containing carbon-metal bonds'. $CH_3MgBr$ (a Grignard reagent) has a carbon-magnesium bond, making it an organometallic compound.

The NCERT biographical note states, 'While attempting to find an efficient catalyst for the process of methylation, he noted that Zn in diethyl ether had been used for this purpose and wondered whether the Mg/ether combination might be successful.'

The synthesis of toluene from bromobenzene (an aryl halide) and methyl bromide (an alkyl halide) using sodium in dry ether fits the description of the Wurtz-Fittig reaction: 'A mixture of an alkyl halide and aryl halide gives an alkylarene when treated with sodium in dry ether and is called Wurtz-Fittig reaction.'

Diphenyl consists of two phenyl groups joined together. This outcome is characteristic of the Fittig reaction, which uses 'Aryl halides also give analogous compounds when treated with sodium in dry ether, in which two aryl groups are joined together. It is called Fittig reaction.'

According to the NCERT text under '6.1.5 General Characteristics of Equilibria Involving Physical Processes', point (iii) states: 'All measurable properties of the system remain constant.' Option 1 is incorrect because equilibrium is possible only in a closed system. Option 2 is incorrect because opposing processes occur at the same rate, and the condition is dynamic but stable. Option 4 is incorrect because the magnitude of such quantities at any stage indicates the extent to which the physical process has proceeded before reaching equilibrium.

The NCERT text states: 'When the rates of the forward and reverse reactions become equal, the concentrations of the reactants and the products remain constant. This is the stage of chemical equilibrium. This equilibrium is dynamic in nature...' Options 1 and 4 describe specific cases of equilibrium, not a general characteristic. Option 2 contradicts the dynamic nature of equilibrium.

The NCERT text specifically states: 'Thus, at equilibrium, the rate of evaporation is equal to the rate of condensation.' This indicates a dynamic equilibrium where opposing processes occur at equal rates.