Volumetric Analysis 2

Solid sodium hydroxide CANNOT be weighed accurately for preparing a standard solution because

• it is corrosive.

• it decomposes easily.

• it is volatile.

• it absorbs moisture from the air.

The following diagram shows the initial and final burette readings.

What was the volume of sodium hydroxide solution used?

• 28.20 cm³

• 28.80 cm³

• 29.20 cm³

• 29.80 cm³

25.0 cm³ of sodium hydroxide solution is tritrated against 0.200 mol dm^–3 hydrochloric acid until the indicator just changes colour. 27.5 cm³ of the acid are required to reach the end point.

Which of the following pieces of apparatus should be used to transfer 25.0 cm³ of the sodium hydroxide solution?

• Burette

• Measuring cyclinder

• Pipette

• Volumetric flask

25.0 cm³ of sodium hydroxide solution is tritrated against 0.200 mol dm^–3 hydrochloric acid until the indicator just changes colour. 27.5 cm³ of the acid are required to reach the end point.

Phenolphthalein is used as an indicator in the above experiment. What will be its colour change at the end point?

• From red to yellow

• From red to colourless

• From yellow to colourless

• From yellow to red

25.0 cm³ of sodium hydroxide solution is tritrated with 0.200 mol dm^–3 hydrochloric acid until the indicator just changes colour. 27.5 cm³ of the acid are required to reach the end point.

What is the molarity of the sodium hydroxide solution?

• 0.100 mol dm^-3

• 0.110 mol dm^-3

• 0.200 mol dm^-3

• 0.220 mol dm^-3

In an experiment to determine the concentration of H₂SO₄ in a brand of toilet cleanser, 10.0 cm³ of the cleanser was first diluted to 250.0 cm³ with distilled water. 25.0 cm³ of the diluted cleanser were titrated with 0.320 mol dm^–3 NaOH solution, using methyl orange as indicator.

What is the colour change of the indicator at the end point of the titration?

• From colourless to pink

• From pink to colourless

• From yellow to red

• From red to yellow

In an experiment to determine the concentration of H₂SO₄ in a brand of toilet cleanser, 10.0 cm³ of the cleanser was first diluted to 250.0 cm³ with distilled water. 25.0 cm³ of the diluted cleanser were titrated with 0.320 mol dm^–3 NaOH solution, using methyl orange as indicator.

If 29.2 cm³ of NaOH solution is used, what is the concentration of H₂SO₄ in the undiluted toilet cleanser?

• 2.30 mol dm^–3

• 4.60 mol dm^–3

• 9.20 mol dm^–3

• 11.50 mol dm^–3

In an experiment, 30.0 cm³ of a monobasic acid HA(aq) were titrated with 0.100 mol dm^–3 NaOH(aq). The following graph shows the variation of pH of the solution mixture during the titration:

What is the concentration of HA(aq)?

• 7.50 x 10^–5 mol dm^–3

• 1.50 x 10^–4 mol dm^–3

• 7.50 x 10^–2 mol dm^–3

• 1.50 x 10^–1 mol dm^–3

The table above lists the pH ranges for colour change of three acid-alkali indicators:

Which of the indicators is / are suitable for the titration in question 8?

• Bromocresol green only

• Phenolphthalein only

• Bromocresol green and methyl red only

• Methyl red and phenolphthalein only

25.0 cm³ of 0.30 mol dm^–3 sodium hydroxide solution require 20.0 cm³ of a 0.125 mol dm^–3 acid solution for complete neutralization. What is the basicity of the acid?

• 1

• 2

• 3

• 4