(CHEM) Topic 8 - Acids and bases

Bronstead-Lowry acid

Proton/hydrogen ion donor

Bronstead-Lowry base

Proton/hydrogen ion acceptor

AMPHIPROTIC definition

A species that can act as both Bronsted-Lowry acids and bases

Bronstead-Lowry bases must contain …

A lone pair

When a Bronstead-Lowry base accepts a proton it forms … with it

A dative bond

A conjugate acid-base pair differ by …

A single proton

A conjugate base has …

One less proton

A conjugate acid has …

One more proton

All Bronstead-Lowry acid-base reactions are …

A reversible process

AMPHOTERIC definition

A species that can act as both an acid and a base

2 examples of amphiprotic species’

H₂O, HCO^3-

Neutralisation reactions are (exo/endo)

Exothermic

Neutralization reactions only produce …

Salt and water

Acid + metal hydroxide →

Salt and water

Acid + metal oxide →

Salt and water

Acid + metal carbonate →

Salt and water and carbon dioxide

Acid + ammonia →

Salt (and water)

Acid + metal →

Salt and hydrogen

BASE definition

Substances that react with acids in neutralization reactions

ALKALI definiton

Solutions containing hydroxide ions that are formed when bases dissolve in water

SALT definition

Compound formed when the hydrogen ion in an acid is replaced by a metal ion (or ammonium ion)

2 examples of alkalis

NaOH, Ba(OH)₂

Examples of bases

Metal oxides/hydroxides, metal carbonates/hydrogencabonates, ammonia

What is a full ionic equation

An equation with all components broken down into ions.

What is a net ionic equation

An equation that only looks at the participating ions and disregards spectator ions

Net ionic equation for all acid + alkali reactions (with state symbols)

H⁺(aq) + OH^-(aq) → H2O(l)

One pH unit represents … change in acidity or basicity

A tenfold

pH scale describes the … of a solution

Hydrogen ion concentration

pH calculation from concentration

pH = -log[H⁺]

[H⁺] =

10^-pH

pOH calculation from concentration

pOH = -log[OH^-]

[OH^-] =

10^-pOH

What is K_w

Ion product constant of water

[H⁺(aq)] > [OH^-(aq)] (Solution is…)

Solution is acidic

[H⁺(aq)] < [OH^-(aq)] (Solution is…)

Solution is alkaline

pH + pOH =

14

What do strong and weak acids differ in?

Extent of ionization

Acid-base equlibria lie in the direction of the (stronger/weaker) conjugate?

Weaker

What happens to strong acids and bases in water?

Dissociate almost compleately

What happens to weak acids and bases in water?

Dissociate only partially

On which side does the equilibrium lay in dissociation reactions of strong acids and bases?

On the left (side of the reactant)

On which side does the equilibrium lay in dissociation reactions of weak acids and bases?

On the right (side of the products)

The stronger the acid the … its conjugate base and vice versa

Weaker

Do strong acids and bases conduct well?

Yes (in solution)

3 methods of distinguishing strength of acids/bases of same concentration

• Compare pH

• Compare conductivity

• Compare rate of reaction with reactive metals (Mg) by measuing gas productionmeasuring

Which has a higher conductivityand why: strong or weak acids/bases?

Strong - more ions to carry charge

Which will produce more gas and therefore has a higher reaction rate with reactive metals: strong or weak acids/bases?

Strong