Hard water

1. In a titration 10 cm3 of sulfuric acid solution was used to neutralise 30 cm3 of 0.1 mol/dm3 potassium hydroxide solution. What was the concentration of the sulfuric acid? Number of moles of KOH V= 30 cm3 = 30/1000=0.03 dm3 n= c x v= 0.1 x 0.03 = 0.003 moles KOH 2) Number of moles of H2SO4. H2SO4 + 2KOH → K2SO4 + 2H2O 0.003 moles KOH react with 0.0015 moles of H2SO4

2. In a titration 10 cm3 of sulfuric acid solution was used to neutralise 30 cm3 of 0.1 mol/dm3 potassium hydroxide solution. What was the concentration of the sulfuric acid? 2) Number of moles of H2SO4. H2SO4 + 2KOH → K2SO4 + 2H2O 0.003 moles KOH react with 0.0015 moles of H2SO4 3) Concentration of sulfuric acid V= 10 cm3 =10/1000=0.01 dm3 C = n/ v= 0.0015/0.01= 0.15 mol / dm3

3. Hard water • L.O: • Determine whether a sample of water is hard or soft. • Consider advantages and disadvantages of hard water

4. P3 test on Monday

6. Hard water: It contains dissolved substances as calcium and magnesium salts The calcium and magnesium ions react with soap producing a precipitate called scum.

9. CaHCO3 → CaCO3 + H2O + CO2

11. In pairs: discuss advantages and disadvantages of hard water.

13. Workbook page 119.