Acids & Bases

Question 1

Why is water special?

Answer 1

It is amphiprotic, meaning it can act as a proton donor or acceptor (acid or base)

Question 2

What does an acid act as?

Answer 2

A proton donor, they give protons in the form of H^+

Question 3

What does a base act as?

Answer 3

A proton acceptor, they accept protons in the form of H^+

Question 4

What happens with NaOH and HCl, if they are placed next to each other in water?

Answer 4

The Na^+ and OH^- break up and the H^+ and Cl^- break apart, the OH^- attracts the H^+ and form H2O

Question 5

What are conjugate acid and base pairs?

Answer 5

Conjugate acid and base pairs are when you have an acid that gives away an H+ ion and becomes a base and a base which accept an H+ ion and become an acid

Question 6

What do conjugate acid and base pairs always have a difference of?

Answer 6

One H^+ ion

Question 7

What happens when water acts as a base?

Answer 7

H2O gives a proton to become a base (OH^-)

Question 8

What happens when water acts as an acid?

Answer 8

H2O accepts a proton to become an acid (H3O^+)

Question 9

Why are acids and bases conductive?

Answer 9

Acids and bases are conductive because they produce ions; acids produce hydronium ions in solution, while bases produce hydroxide ions

Question 10

Why are strong acids and bases better conductors of electricity than weak acids and bases?

Answer 10

When strong acids and bases react, they produce ions in a 1:1 mole ratio and so a large amount of ions are formed. With a higher amount of ions produced than weak acids and bases at the same concentrations, solutions of strong acids or bases have greater electrical conductivity than solutions of weak acids and bases. This is because weak acids and bases partially disassociate, whereas strong acids and bases fully dissociate.

Question 11

What is Kw?

Answer 11

The dissociation constant of water (Kc for water)

Question 12

What is the value of Kw?

Answer 12

1 x 10^-14

Question 13

How do you solve Kw problems?

Answer 13

• Make x = [H3O^+] and {OH^-]
• x^2 = 1 x 10^-14
• x = 1 x 10^-7

Question 14

What can water dissociate into?

Answer 14

Hydronium and hydroxide ions

Question 15

Describe acids in terms of pH

Answer 15

Strong acids will have high concentrations of H3O^+ ions, which will give them a lower pH (1-3)

Weak acids will have low concentrations of H3O^+ ions, which will give them a higher pH (4-6)

Question 16

Describe bases in terms of pH

Answer 16

Strong bases will have high concentrations of OH^- ions, which will give them a higher pH (11-14)

Weak bases will have low concentrations of OH^- ions, which will give them a lower pH (8-10)

Question 17

What must you remember when calculating pH?

Answer 17

To pay attention to whether the given mol/L is an acid or base. If it’s an acid, go straight to the calculation. If it’s a base, first work out [H3O^+] and then do the calculation.

Question 18

What are acidic salts?

Answer 18

Salts that produce acidic solutions when added to H2O

Question 19

How does NH4Cl produce an acidic solution?

Answer 19

When NH4Cl is added to water, dissociation occurs

NH4Cl(s) →(H2O) NH4^+(aq) + Cl^-(aq)

The NH4 ions will act as a proton donor to water

NH4^+ (aq) + H2O(l) ⇌ NH3(aq) + H3O^+(aq)

The resulting solution is acidic

Question 20

What are basic salts?

Answer 20

Salts that produce basic solutions when added to H2O

Question 21

How does Na2CO3 produce a basic solution?

Answer 21

When Na2CO3 is added to water, dissociation occurs

Na2CO3(s) →(H2O) 2Na^+(aq) + CO3^2-(aq)

The CO3^2- ions will act as a proton acceptor from water

CO3^2-(aq) + H2O(l) ⇌ HCO3^- + OH^-

The resulting solution is basic

Question 22

What happens to the concentrations of hydronium and hydroxide ions when an acid is being added to a solution?

Answer 22

The concentration of hydronium ions increases while concentration of hydroxide decreases

Question 23

What happens to the concentrations of hydronium and hydroxide ions when a base is being added to a solution?

Answer 23

The concentration of hydronium ions decreases while concentration of hydroxide increases