Acid + Base titrations

What is a titration

Quantitative determination of the concentration of compounds in a solution

Acid-base titration: An application of acid-base WHAT, reaction WHAT

1. WHAT

2. WHAT

3. WHAT

Acid-base titration: An application of acid-base EQUILIBRIA, reaction STOICHOMETRY

1. Strong acid - strong base

2. weak acid - strong base

3. Strong acid - weak base

How do you follow the progress of titration:

1. WHAT 

2. WHAT 

How do you follow the progress of titration:

1. Potentiometric titration  

2. Visual titrations 

Potentiometric titration you can add WHAT uses a WHAT 

Potentiometric titration you can add WATER uses a pH METER 

Visual titrations can add WHAT uses a WHAT 

Visual titrations can add WATER (concentration changes NOT moles) uses a INDICATOR 

What is a titrant

Solution in which you know the IDENTITY and CONCENTRATION of

What is a titrand / analyte

Unknown CONCENTRATION and unknown IDENTITY

What is an equivalence point:

What is an endpoint:

What is an equivalence point: Ideal, theoretical

• No limiting reagent

• Exact amount of titrant added

What is an endpoint: Actual, experimental

• Determined visually

• Value dependent on technique used

What is a ½ equivalence point

• nA = nHA

• pH = pKa

• This can help you identify the identity of the acod

Before equivalence point

• Excess H3O+ in solution

• pH determined bu [H3O+]

At equivalence point

• Acid exactly neutralized

After equivalence point

• Excess OH- in solution

• pH determine by [OH-]

Which titration would you use for determining concentration of an unknown species

• Potentiometric titration

• Visual titration

Which titration would you use for determining the IDENTITY of an unknown acid

• Potential titration

What factors affect the titration curve shape

1. [acid]

2. Identity of acid

3. [base] (only care about the number of mols)

Initial pH can be affected by WHAT

• Initial CONCENTRATION of HA (pH = -log[HA])

• STRENGTH of HA (Ka)

Volume to reach equivalence point depends on WHAT 

• Number of MOLES of HA in solution (nH3O+ = nOH-)

• CONCENTRATION of STRONG BASE used ([base] + nOH- = nH3O+)

pH at the equivalence point

• Slightly basic if titrating a WEAK ACID

• The STRONGER the HA, the WEAKER the conjugate base and the closer the pH is to 7

pH at the half-equivalence point depends on WHAT

Strength of the HA (pH = pKa → find Ka - find the identity and strength of the acid) 

Based on this graph what indicator would you use for a strong acid and for a weak acid 

Strong acid = any of the three indicators listed 

Weak acid = Phenolphthalein 

A good indicator should have a WHAT value close to the expected WHAT at the equivalence point 

A good indicator should have a pKa (In) value close to the expected pH at the equivalence point