Chemistry

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54. Options (i) and (iii) are correct since nucleophiles are negatively charged or electron rich (as contains lone pair of electrons) species. 

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Alkali metals are ionic in nature due to their larger size. They have +1 oxidation states. Alkali metals forms three types of oxides such as peroxides, superoxides and normal oxides. The basic character of normal oxides increases from lithium oxide to caesium oxide.

The halides of alkali metals are also ionic except lithium halide. Lithium halide is covalent in nature because of small size and high polarizing power.

Oxosalts of alkali metal are solid water-soluble ionic compounds. Oxosalts of lithium show different properties due to small size of lithium.

This is a Multiple Choice Questions as classified in NCERT Exemplar

55. Options (i) and (iii) are correct since nucleophiles are negatively charged or electron rich (as contains lone pair of electrons) species. 

This is a Multiple Choice Questions as classified in NCERT Exemplar

53. Options (i) and (ii) are correct since two or more compounds with same molecular formula but different functional groups are known as functional isomers. In the given compounds- 

I. Aldehydic group. II. Ketonic group. III. Ketonic group. IV. Aldehydic group. So, II and III, I and IV are not functional isomers.

This is a Multiple Choice Questions as classified in NCERT Exemplar

52. Option (ii) II and III since in position isomerism, two or more compounds differ in the position of substituents, functional group, or multiple bonds but their molecular formula is same. In pentanone-2 and pentanone-3, position of ketonic group is different. CH₃-CH₂-CH₂-CO-CH₃ and CH₃ - CH₂-CO-CH₂- CH₃

This is a Multiple Choice Questions as classified in NCERT Exemplar

51. Options (ii) and (iii) are correct since the electrophiles are positively charged or electron deficient species. They act as Lewis acids. AlCl₃, SO₃are Lewis acids while  NO₂⁺, CH₃⁺, CH₃-C⁺ = O are positively charged species. Therefore, the species involved in the above-mentioned options act as electrophiles.

This is a Multiple Choice Questions as classified in NCERT Exemplar

50. Options (i), (iii) and (iv) are correct since the spatial arrangement of groups or atoms can be checked by doing two interchanges and bringing the H atom below the plane of the paper. Then find out the sequence of the left-out groups in a particular order whether clockwise or anticlockwise starting from the atom with the highest atomic number to the atom with lower atomic numbers. So, out of the given options option (ii) has the same spatial arrangement as (A) while in rest three spatial arrangements are different.

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49. Options (i) and (iv) are correct since only in these two compounds all the carbon atoms are having same hybridization i.e., sp hybridized in option (i) and sp2 hybridized in option (iv).

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48. Option (ii) is correct since the arrow shows the direction of electron transfer. In the given reaction, the electron flows from π bond towards the electron-deficient H⁺ group . This can be represented as-

This is a Multiple Choice Questions as classified in NCERT Exemplar

47. Bromine is found to be more electronegative than Carbon which leads to heterolytic fission. Due to the higher electronegativity the electrons displace from carbon to Br. Therefore, CH₃ gets positive charge and Br gets negative charge and hence option (ii) is found to be the correct one.