16.2.5 Lewis Acids and Bases

Question 1

Lewis Acids and Bases

Answer 1

• A Lewis acid accepts electron pairs and a Lewis base donates electron pairs.
• A Lewis acid-base reaction may give rise to a Brønsted-Lowry acid.
• Baking powder contains baking soda and a Lewis acid in a solid form.

Question 2

note

Answer 2

• A Brønsted-Lowry acid donates a proton and a
  Brønsted-Lowry base accepts a proton.
• A Lewis acid accepts an electron pair and a Lewis base
  donates an electron pair.
• Coordinate covalent bonds are formed when electrons come from just one partner (nitrogen in this case).
• A Lewis acid-base reaction may give rise to a Brønsted- Lowry acid.
• For example, water (a Lewis base) reacts with carbon dioxide (a Lewis acid) to yield carbonic acid (a Brønsted-Lowry acid). Carbonic acid gives rise to carbonation in sodas and other carbonated beverages.
• Baking powder contains a Lewis acid in solid form (such as Al 2 (SO 4 ) 3 ), as well as baking soda.
• In a multi-step reaction sequence, the aluminum cation reacts with water to form a charged complex, the charged complex reacts with water to form hydronium ion, and the hydronium ion reacts with bicarbonate anion to produce carbon dioxide and water. The carbon dioxide gas causes baked goods to rise.

Question 3

Why did G. N. Lewis feel it was necessary to extend the definition of acids?

Answer 3

The new definition covered a wider range of reactions.

Question 4

Lewis acids include reactions not satisfactorily explained by the Brønsted model. For which of the following reactions is the Brønsted model satisfactory (which means the Lewis definition is not necessary)?

Answer 4

The reaction of HCl gas and water to form hydronium ions and chloride ions

Question 5

Silver chloride, AgCl, is only slightly soluble in water. The solubility can be increased by adding which of the following?

Answer 5

NH3

Question 6

Which one of the following is LEAST likely to act as a Lewis base?

Answer 6

Os3+

Question 7

Which of these species can act as a Lewis acid?

Answer 7

NO2

Question 8

Which one of the following is unlikely to act as a Lewis base?

Answer 8

Cr3+

Question 9

Which of the following statements is not true?

Answer 9

A proton can act as a Lewis base.

Question 10

Which of these species is more likely to act as a Lewis acid in reactions?

Answer 10

Mn2+

Question 11

Which of the following describes a Lewis acid?

Answer 11

An electron pair acceptor.