Class 11th

This is a Long Type Questions as classified in NCERT Exemplar

The factors that affects electron gain enthalpy are as follows:

(a) Effective nuclear charge with its increase the electron gain enthalpy also increases

(b) Atomic size with its increase the electron gain enthalpy decreases

(c) The e-e - repulsion with its increase the electron gain enthalpy decreases

(d) Whenever there exists half filled or completely filled orbital than it lead to decrease the electron gain enthalpy because it leads to give extra stability to the atom due to symmetry

The electron gain enthalpy decreases down the group and increases across the period.

This is a Matching Type Questions as classified in NCERT Exemplar

(i)→ (a), (d); (ii)→ (c); (iii)→ (a); (iv)→ (b)

This is a Matching Type Questions as classified in NCERT Exemplar

(i)→ (e); (ii)→ (d); (iii)→ (a); (iv)→ (b) ; (v)→ (c)

This is a Matching Type Questions as classified in NCERT Exemplar

(i)→ (d); (ii)→ (e); (iii)→ (a); (iv)→ (c) ; (v)→ (b)

This is a Matching Type Questions as classified in NCERT Exemplar

(i)→ (c); (ii)→ (d); (iii)→ (b); (iv)→ (a)

This is a Multiple choice Questions as classified in NCERT Exemplar

Options (i) and (ii) are correct since 75% of the solar energy reaching the earth is being absorbed by the earth's surface and this increases its temperature. The rest of the heat radiates back to the atmosphere. The average global temperature will increase to a level, and this leads to melting of polar ice caps and flooding of low-lying areas all over the earth. Increase in the global temperature increases the incidence of inectious diseases like malaria, dengue,   yellow fever etc.

This is a Multiple choice Questions as classified in NCERT Exemplar

Options (ii), (iii) and (iv)  are correct since rainwater has a pH of 5.6 due to the presence of H+ ions formed by the reaction of rainwater with carbon dioxide present in the atmosphere. The reactions can be shown as-

H₂O (l)+CO₂ (g)→H₂CO₃ (aq)

H₂CO₃ (aq)→H+ (aq)+HCO₃ (aq)

If the pH of the rainwater falls below 5.6 then it is known as acid rain. SO₂ and NO₂ after oxidation and reaction with water are major contributors to the acid rain.

2SO₂ (g)+O₂ (g)+2H₂O (l)→2H₂SO₄ (aq)

4NO₂ (g)+O₂ (g)+2H₂O (l)→4HNO₃⁻ (aq)

This is a Multiple choice Questions as classified in NCERT Exemplar

Options (i) and (ii) are correct since fertilizers contain phosphates as additives. The addition of phosphates in water enhances the growth of the algae. Such profuse growth of algae covers the water surface and reduces the oxygen concentration in water.

This is a Multiple choice Questions as classified in NCERT Exemplar

Options (iii) and (iv) are correct since clean water has BOD less than 5 ppm and polluted water has BOD value higher than 5 ppm. So, 10 BOD means highly polluted water. This process in which nutrient enriched water bodies support a dense plant population, which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is termed as Eutrophication.

This is a Multiple choice Questions as classified in NCERT Exemplar

Option (iv)

Using plastic cans for neatly storing substances is correct since use of plastic cans for neatly storing substances will not come under green chemistry because plastic is non-biodegradable and causes pollution.