Titration

Which solution would you place in a conical flask

• Standard solution

• Unknown concentration solution

• indicator

Choose the indicator solutions used for acid-base titration

• Phenolphtalein solution

• Methyl red solution

• Methyl orange solution

• Fluoresceine solution

From the list of indicators shown, choose one that is suitable for this reaction.

• Phenolphthalein
• Bromophenol Blue
• Bromocresol Green
• Any indicator can be used and an accurate result will be obtained.

A student wishes to determine the concentration of a weak acid by titration with a base of known concentration.

What is the most important property of the base?

• it should be weak

• it should be strong

• it should be a primary standard

• it should not react with carbon dioxide

What type of reaction is taking place here

• fertiliser

• titration

• acid

• neutralisation

Which statement best describes the equivalence point in a titration between a strong acid and a strong base?

• the point at which the first sign of a colour change occurs

• the point at which equal moles of acid and base have been added together

• the point at which the rate of the forward reaction equals the rate of the reverse reaction

HCl + NaOH → 

• NaH + ClOH
• NaCl + H₂
• NaCl + H₂O
• NaCl + Cl₂

2018 Q17

A clear, colourless liquid extract of the rhubarb plant was analysed for the concentration of oxalic acid, H2C2O4, by direct titration with a recently standardised and acidified potassium permanganate solution, KMnO4(aq).

The balanced equation for this titration is shown below.

2MnO₄^–(aq) + 5C₂O₄ ^2–(aq) + 16H⁺(aq) → 2Mn²⁺(aq) +

purple colourless colourless

10CO₂(g) + 8H₂O(l)

The steps in the titration were as follows:

Step 1 – A 20.00 mL aliquot of the rhubarb extract was placed in a 200 mL conical flask.

Step 2 – The burette was filled with acidified 0.0200 M KMnO4 solution.

Step 3 – The acidified 0.0200 M KMnO₄ solution was titrated into the rhubarb extract in the conical flask. The

titration was considered to have reached the end point when the solution in the conical flask showed a

permanent change in colour to pink. The volume of the titre was recorded.

Step 4 – The titration was repeated until three concordant results were obtained. The average of the concordant titres was 21.7 mL.

The concentration of H₂C₂O₄ in the rhubarb extract is closest to

• 5.43 × 10^–2 M

• 5.00 × 10^–2 M

• 2.17 × 10^–2 M

• 7.40 × 10^–4 M

In a titration of a strong base with a strong acid, the following procedure was used:

1. A burette was rinsed with water and then filled with the standard acid.

2. A pipette was rinsed with some base solution.

3. A conical flask was rinsed with some base solution.

4. A pipette was used to transfer a measured volume of base solution into the conical flask.

5. Indicator was added to the base sample and it was titrated to the endpoint with the acid.

Which statement is correct?

• the calculated base concentration will be correct

• the calculated base concentration will be too low

• the calculated base concentration will be too high

• no definite conclusion can be reached about the base concentration

What is the solution of unknown concentration, but known volume, called?

• Analyte

• Titrant

• Indicator

• Titration