CHEM Unit 3 - Acids and Bases

Ionisation

ionic solids forming ions in solution, with the more electronegative atom holding the shared pair of electrons.

Dissociation

breaking apart of molecules into ions in solution

Davy's Model

• acids contain replacable hydrogen, bases react to form salts and water

Hydrolysis of Neutral Species (Salts)

• neutral species will not undergo hydrolysis

Conjugate bases of strong acids

tend to be weak

Conjugate bases of weak acids

tend to be strong bases

Conjugate acids of weak bases

tend to be strongly acidic

Requirements for a Primary Standard

• high purity, low reactivity, high molar mass, not hygroscopic, be soluble in a suitable solvent

Equivalence Point

point during a titration where amount of titrant is enough to neutralise analyte solution. Number of moles matches molar ratio of equation. when neither acid nor base remain

End Point

point in which indicator changes colour permenantly

What should volumetric flask be rinsed with

rinsed with distilled water

what should beaker be rinsed with

with solution to be placed in it

what should pipette be rinsed with

rinsed with solution it will draw

what should burette be rinsed with

rinsed with titrant

what should conical flask be rinsed with

rinsed with distilled water

Buffer Capacity

• ability of a buffer to resist a change in pH

limitations of Arrhenius Theory

• acids and bases are only in aqueous solutions.

• It cannot deal with gases.

• it only accounts for substances which already have hydrogen or hydroxide in their structure

• unable to identify salts as acidic or basic

Strongest bases have (Ka values)

the lowest Ka value, but highest Kb value

neutral ions (10 of them)

• Li+

• Na+

• K+

• Mg2+

• Ca2+

• Ba2+

• Cl-

• Br-

• I-

• NO3-

Salt Hydrolysis defo

when ions in a salt are interfering with the self-ionisation of water

Amphoteric

substance that can act as both a bronsted lowry acid or base

Arrhenius Theory

• in solutions, acids produce H+ ions

• in solutions, bases produce OH- ions

• must write reversible arrow for all reactions

Bronsted-Lowry Model

• acids act as proton donors

• bases act as proton acceptors

Neutral Solution

• a solution that contains the same concentration of H+ ions as OH-

Why Strong acids/bases dont produce buffers

• to produce a buffer a reversible reaction is required

• reaction between strong acid and strong base is not reversible

Buffer

• a solution of a weak acid/conjugate base pair or base/conjugate acid that can resist a change in pH when a small amount of acid or base is added to it

• metal oxides are ___

• non-metal oxides are ___

• metal oxides are basic (e.g Cobalt Oxide)

• non-metal oxides are acidic (e.g Carbon Dioxide)