Chemistry

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The flame is due to the excitation of the electron from its higher energy state to the lower energy states. Due to the small atomic and ionic size of beryllium and magnesium, electrons are tightly bound to the atom. The electrons of Be and Mg does not gain excitation from the energy provided by the flame. Hence they do not show any flame in the flame test.

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64. Option (iii) i.e., Both A and R are not correct is the answer since sulphur is estimated by Carius method in the form of white precipitate of BaSO₄ on heating with fuming and BaCl₂. If light yellow solid is obtained means impurities are present. It is filtered, washed and then dried to get pure BaSO₄ . 

This is a short answer type question as classified in NCERT Exemplar

The lewis structure of O₂^– ion is,

Oxygen atom having no charge has 6 electrons, so its oxidation number is zero. Oxygen atoms containing −1 charge have 7 electrons, so its oxidation number is −1. The average oxidation state of oxygen in this ion is, =1/2

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63. Option (iv) i.e., A is not correct, but R is correct is the answer since hybridization of C can be found out by counting σ bonds and π bonds present on C atom. This can be shown as-

If C has 3σ bonds then it is sp² hybridized. If C has 2σ bonds then it is sp hybridized.

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In the Solvay process, carbon dioxide is transferred through a concentrated solution of ammoniacontaining sodium chloride, which forms ammonium carbonate followed by ammonium hydrogen carbonate. The chemicals in ammonium hydrogen carbonate are different and are heated to form sodium carbonate. NH₃ is found in a solution containing NH₄Cl that is heated and treated with Ca (OH)₂? The reaction of (NH₄)2CO₃ with NaCl provides two products, Na₂CO₃ and NH₄Cl both soluble in water which do not shift to the right balance.

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Ionic compounds are formed from the alkali metals due to their large ionic size and low ionization enthalpy. Thus, they are soluble in water. But, due to the small ionic size, high ionization enthalpy, and high electronegativity of lithium, it forms compounds of covalent nature and thus, are soluble in organic solvents.

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62. Option (i) i.e.,  

Both A and R are correct, and R is the correct explanation of A is the answer as when two or more compounds differ in the position of substituent atom or functional group on the carbon skeleton, they are known as position isomers and this phenomenon is termed as position isomerism. Pent-2-ene and pent-l-ene are position isomers because they differ in the position of the double bond. 

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61. Option (iv)

i.e.,   A is not correct, but R is correct is the answer. This is because canonical structures always have more energy than the resonance hybrid. Resonance hybrids are always found to be more stable than any of the canonical structures since the delocalization of electrons lowers the orbitals energy and gives stability.

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BeSO₄ and MgSO₄ readily soluble in water while CaSO₄, SrSO₄ and BaSO₄ are insoluble The greater hydration enthalpy of Be²⁺ and Mg²⁺ ions overcome the lattice enthalpy factor and therefore, their sulfates are soluble.

This is a Assertion Type Questions as classified in NCERT Exemplar

60. Option (i)

i.e.,   Both A and R are correct, and R is the correct explanation of A is the answer. Since the liquids are having sufficient difference in their boiling points. Liquids having different boiling points vaporize at different temperatures. The vapours are cooled, and the liquids so formed are collected separately.