1)Sodium hydroxide is a strong alkali.

In terms of ionisation, what is meant by the word strong? ( 1 mark)

2) You are given solutions of sodium hydroxide and ammonia of the same concentration. Describe and give the results of a test to show that sodium hydroxide is a stronger alkali than ammonia solution. (2 marks)

1)Sodium hydroxide is a strong alkali.

In terms of ionisation, what is meant by the word strong? ( 1 mark)

• completely ionised /dissociated

2) You are given solutions of sodium hydroxide and ammonia of the same concentration. Describe and give the results of a test to show that sodium hydroxide is a stronger alkali than ammonia solution. (2 marks)

• pH paper / (pH) meter (1)

NaOH has higher pH or

• correct comparison of colours (1 mark)

Titration calculations

L.O.:

Calculate the amount of acid or alkali needed in a neutralisation reactions

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What is concentration?

The concentration of a solution is a measure of how much solute is dissolved per unit of solvent.

amount of solute is measured in moles

volume of solvent is measured in dm3

concentration is measured in mol dm-3.

concentration = amount of solute / volume of solvent

Volumes are often expressed in cm3, so a more useful equation includes a conversion from cm3 to dm3.

concentration = (no. moles × 1000) / volume

mol dm3 cm3

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Concentration, moles and volume

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Concentration calculations

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Titration calculations examples

What is the concentration of an NaOH solution if 25.0 cm3 is neutralized by 23.4 cm3 0.998 mol dm-3 HCl solution?

3. Calculate no. moles of NaOH:

0.0234 moles HCl = 0.0234 moles NaOH

4. Calculate conc. of NaOH: = (0.0234 × 1000) / 25.0

conc. = (moles × 1000) / volume

= 0.936 mol dm-3

1. Calculate no. moles HCl:

moles = (conc. × volume) / 1000

= 0.0234= (0.998 × 23.4) / 1000

2. Determine ratio of NaOH to HCl:

NaOH + HCl NaCl + H2O

ratio NaOH:NaCl = 1:1

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Titration calculations

• Task:

• Worksheet (moles14)

• Workbook 113-114