Acids and bases

Question 1

Arrhenius Acids

Answer 1

Produce H+ in H20

Question 2

Arrhenius bases

Answer 2

Produce OH- in H20

Question 3

Fail of Arrhenius’s theory

Answer 3

• Does not take into consideration the role of solvent
• Cannot explain why substances lacking hydroxide ions, such as NH3, are bases
• Does not describe accurately the H+ state, which does not exist as such in water

Question 4

Amphoteric substances

Answer 4

Able to act both as acid or base

Question 5

NH3 and H20 reaction

Answer 5

NH3 acts as the base that accepts H+
H2O acts as the acid that donates H+
Because the N atom of NH3 has a stronger attraction for H+ than oxygen

Question 6

Lewis’ acid and bases

Answer 6

Acids: Accept an electron pair
Bases: Donate an electron pair

Question 7

Conjugate acid-base pairs

Answer 7

In any acid-base reaction, there are two conjugate acid-base pair, related by the loss and gain of one H+

Question 8

Strengths of Acids and Bases

Answer 8

• Weak acids only partially dissociate in water
• Strong acids completely ionizes in aqueous solutions
• Strong bases ( strong electrolytes) are formed from metals of Group 1A and 2A, they dissociate completely in water
• Weak bases ( weak electrolytes), poor acceptors of H+ ions, produce very few ions in solution

Question 9

Diprotic acids

Answer 9

Acids that have two H+, which dissociate one at a time

Question 10

Direction of an acidic reaction

Answer 10

As the strength of the acid decreases, the strength of its conjugate base increases.
By comparing their relative strengths, we can determine
the direction of the reaction (to reach equilibrium, the strong acid and strong base react in the direction of the weaker acid and weaker base)

Question 11

Acid dissociation constant

Answer 11

Used to determine the strength of an acid
When Ka is small, equilibrium lies to the left, favoring the reactants
When Ka is large, equilibrium lies to the right, favoring the products

Question 12

Base dissociation constant

Answer 12

Kb
- is small, the equilibrium lies to the left, favoring the
reactants.
- is large, the equilibrium lies to the right, favoring the products.

Question 13

Why can water act either as a base or acid

Answer 13

In water it dissociates in OH- e H30+

Question 14

Water dissociation constant

Answer 14

Kw
The product of the concentrations of H3O+ and OH−.
Equal to 1.0 ́ 10−14 at 25 °C.

Question 15

pH scale

Answer 15

Used to describe the acidity of solutions
acidic < 7
neutral= 7
basic > 7
pH= - log (H3O+)
pH decreases as the [H3O+] increases.

Question 16

How to calculate the concentration

Answer 16

Si calcola facendo il rapporto tra le moli di soluto e il volume della soluzione (l solvente + l soluto)