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1)Sodium hydroxide is a strong alkali

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1 1)Sodium hydroxide is a strong alkali
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)

2 1)Sodium hydroxide is a strong alkali.
In terms of ionisation, what is meant by the word strong? ( 1 mark) completely ionised /dissociated

3 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)

4 Boardworks AS Chemistry Chemical Calculations
Titration calculations L.O.: Calculate the amount of acid or alkali needed in a neutralisation reactions Moles 14

5 Boardworks AS Chemistry Chemical Calculations
What is concentration? Boardworks AS Chemistry Chemical Calculations The concentration of a solution is a measure of how much solute is dissolved per unit of solvent. concentration = amount of solute / volume of solvent amount of solute is measured in moles volume of solvent is measured in dm3 concentration is measured in mol dm-3. Volumes are often expressed in cm3, so a more useful equation includes a conversion from cm3 to dm3. Teacher notes The use of the term ‘molarity’ and the symbol ‘M’ to represent mol dm-3 are no longer recommended. It should be clarified to students that if the amount of solute is expressed as a mass, then the equation above calculates the ‘mass concentration’ (measured in g dm-3), which is different from just ‘concentration’. concentration = (no. moles × 1000) / volume mol dm3 cm3

6 Concentration, moles and volume
Boardworks AS Chemistry Chemical Calculations

7 Concentration calculations
Boardworks AS Chemistry Chemical Calculations

8 Titration calculations examples
Boardworks AS Chemistry Chemical Calculations What is the concentration of an NaOH solution if 25.0 cm3 is neutralized by 23.4 cm mol dm-3 HCl solution? 1. Calculate no. moles HCl: moles = (conc. × volume) / 1000 = (0.998 × 23.4) / 1000 = 2. Determine ratio of NaOH to HCl: NaOH + HCl ® NaCl + H2O ratio NaOH:NaCl = 1:1 3. Calculate no. moles of NaOH: moles HCl = moles NaOH 4. Calculate conc. of NaOH: conc. = (moles × 1000) / volume = ( × 1000) / 25.0 = mol dm-3

9 Titration calculations
Boardworks AS Chemistry Chemical Calculations

10 Task: Worksheet (moles14) Workbook


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