2. Acids and Alkalis Can you think of some common, household acids and alkalis? AcidsAlkalis Vinegar Fruit Juice Baking Soda Indigestion Powder Oven Cleaner In Toothpaste USES: WASP STING IS ALKALINE IT IS NEUTRALISED BY VINEGAR AN ACID LIME AN ALAKLI IS ADDED TO ACIDIC SOIL VINEGAR IS USED AS A PRESERVATIVE AMMONIA IS USED AS A HOUSEHOLD CLEANER

3. COMMON LAB ACIDS ACID FORMULA COMMON LAB ALKALIS ALKALI FORMULA HYDROCHLORIC (hydrogen chloride) SODIUM HYDROXIDE SULPHURIC (hydrogen sulphate) POTASSIUM HYDROXIDE ETHANOICAMMONIUM HYDROXIDE NITRIC (hydrogen nitrate) LITHIUM HYDROXIDE HCl(aq) H 2 SO 4(aq) CH 3 COOH(aq) HNO 3(aq) NaOH(aq) KOH(aq) NH 4 OH(aq) LiOH(aq) Laboratory Acids and Alkalis Can you work out the FORMULAS from the name? You MUST remember the FORMULAS of these!!!

4. INDICATORS SUBSTANCES THAT CHANGE COLOUR WITH CHANGING pH pH scale Used to measure acidity or alkalinity of SOLUTIONS Scale runs from under 0 to above 14 01234567891011121314 Neutral 7 only Anything under 7 is acidic Anything above 7 is alkaline Testing for Acids and Alkalis

5. The pH scale is based on the pH of pure water being =7 When we measure the pH of a solution, we are measuring to what degree a solute has changed the pH of water Universal indicator to cover the whole range Red pink orange green blue/green blue purple Strong acid weak acid neutral weak alkali strong alkali The pH Scale

6. 1. Prepare a test solution 2. Add universal indicator (or drop onto pH paper) 3. Allow colour to develop 4. Compare with standard colour chart Rules when testing pH

7. Testing for pH Name of SolutionpHAcid / Alkali / Acid Follow the rules for “Testing pH” and test 5 different solutions

8. Non-metal Oxides Name of oxide Appearance of oxide Universal indicator Sulphur dioxide Carbon dioxide Oxides of nitrogen Hydrogen oxide Colourless, pungent gas Colourless, odourless gas Colourless or brown Pungent gas Colourless and odourless RED GREEN

9. Non-metal Oxides Oxides of carbon and sulphur are prepared by burning sulphur and carbon in air. Oxides of nitrogen are prepared by sparking air RULE: Oxides of NON-METALS make ACIDIC SOLUTIONS EXCEPTION: Oxide of HYDROGEN is NEUTRAL (water)

10. Starter question Which of the following substances when dissolved in water would produce an acidic solution 1)Magnesium oxide 2)Hydrogen oxide 3)Ammonium hydroxide 4)Phosphorus oxide Answer 4) Explanation the rule is soluble non-metal oxides make acidic solutions

11. Metal Oxides Experiment 1: 1. Add a tiny quantity of CALCIUM OXIDE into a dimple tray 2. Add a few drops of WATER 3. Test the pH of the solution with UNIVERSAL INDICATOR Name of Oxide Appearance of Oxide pH of solution

12. Metal Oxides When a metal oxide reacts with water, the METAL HYDROXIDE is formed eg Sodium oxide reacts and forms SODIUM HYDROXIDE Na 2 O (s) + H 2 O (l) 2NaOH (aq)

13. Making Metal Oxides Experiment 2: 1. Ignite a little of MAGNESIUM RIBBON 2. Allow magnesium to burn and form MAGNESIUM OXIDE 3. Drop the white ash onto a dimple tray 4. Check the pH of the SOLUTION Write the balanced equation for making MAGNESIUM OXIDE:

14. RULE: Oxides of METALS make ALKALINE SOLUTIONS HOWEVER: Like non-metal oxides, they must be SOLUBLE in water for them to change the pH of water Metal Oxides

15. Today’s plan: Looking at INSOLUBLE METAL OXIDES AMMONIA GAS and its pH THURSDAY 8th OCTOBER

16. Insoluble Oxides and Hydroxides Experiment: 1. Add a small quantity of copper (II) oxide to a test-tube 2. Add approx 5ml of water 3. Shake the tube and try and dissolve the solid 4. Use a dropper to transfer a sample of the clear liquid to the spotting tile 5. Check the pH with Universal Indicator Some metal oxides (such as copper (II) oxide) are INSOLUBLE in water, as these don’t dissolve, they CANNOT alter the pH of water.

17. Ammonia NH 3(g) is ammonia gas(covalently bonded compound) When dissolved in water ammonium hydroxide is formed The equation for the reaction when ammonia gas dissolves in water to form ammonium hydroxide NH 3 (g) + H 2 O  NH 4 OH(aq) THIS SOLUBLE HYDROXIDE MUST BE AN ALKALI Fountain Experiment

18. Summary Flow-chart

19. Starter Question Put these four oxides in order of the one which will give the HIGHEST pH to the one that will give the LOWEST pH: Hydrogen oxide Magnesium oxide Carbon dioxide Copper (II) oxide (The flow-chart from last day will help you!!)

20. Acids Name of acidFormula Hydrochloric Sulphuric Nitric Ethanoic HCl (aq) H 2 SO 4 (aq) HNO 3 (aq) CH 3 COOH (aq) Which element is COMMON to all acids?

21. Acids Looking at the formula of the acids – which type of BONDING would you expect? Think…….. Would you expect it to CONDUCT ELECTRICITY?? Experiment: 1. Set up the circuit shown 2. Use HYDROCHLORIC ACID and determine if it conducts 3. Repeat with both SULPHURIC and NITRIC ACIDS

22. Acids Acids are: Compounds which dissolve in water to give a pH less than 7 All acids contain the element HYDROGEN Acid solutions are able to conduct electricity

23. Electrolysis of Acids 1.Set up apparatus as shown – using DIRECT CURRENT (DC) 2.Upturn a test-tube FULL OF WATER over each electrode 3.Turn on the power supply – set to 6V 4.Collect a tube-full of gas from one electrode. 5.Keep the tube inverted to prevent losing any gas. 6.Test the tube for HYDROGEN GAS. 7.Repeat for other electrode. Experiment:

24. Electrolysis of Acids Draw a labelled diagram of the apparatus used last day Underneath your diagram copy the note below: Electrolysis is the breaking down of a compound using electricity. When acids undergo electrolysis, HYDROGEN GAS is formed at the negative electrode.

25. Why does hydrogen form? +ve-ve H+H+ e-e- H+H+ H+H+ H+H+ H+H+ H+H+ e-e- e-e- e-e- H H H Although acids are made up of non-metals they exist as IONS. The hydrogen ions (H + ) pick up electrons from the negative electrode and produce hydrogen gas.

26. Ions in Acids

27. Alkalis Think!! What common alkalis have you come across before?? How many can you name??

28. Alkalis Can you now put these into a table? Can you get their formula? Can you work out the IONS present?

29. The pH scale - dilution Experiment: Measure 10ml of acid into test-tube (A) – test pH Take 1ml of A and dilute with 9ml of water (B) – test pH Take 1ml of B and dilute with 9ml of water (C) – test pH Repeat for test-tubes D, E and F – testing pH of each Results: Test-tubepH

30. The pH scale - dilution Answer these questions in your NOTES jotter. Write in sentences – these will be your notes for this activity!! What happens to the ACIDITY as the ACID is diluted? What is happening to the concentration of H (aq) ions? What happens to the pH as the ACID is diluted? +

31. The pH scale - dilution Experiment (This is a repeat of yesterday’s using ALKALI): Measure 10ml of ALKALI into test-tube (A) – test pH Take 1ml of A and dilute with 9ml of water (B) – test pH Take 1ml of B and dilute with 9ml of water (C) – test pH Repeat for test-tubes D, E and F – testing pH of each Results: Test-tubepH

32. The pH scale - dilution Answer these questions in your NOTES jotter. Write in sentences – these will be your notes for this activity!! What happens to the ALKALINITY as the ALKALI is diluted? What happens to the concentration of OH (aq) ions? What happens to the pH as the ALKALI is diluted? -

33. H + (aq) and OH - (aq) Ions NEUTRAL solutions contain an EQUAL concentration of H (aq) and OH (aq) ions. ACIDIC solutions contain a GREATER concentration of H (aq) than OH (aq) ions. ALKALINE solutions contain a GREATER concentration of OH (aq) than H (aq) ions. + + + - - -

34. Water The chemical name for water is HYDROGEN OXIDE The expected bonding is From this bonding COVALENT BONDING WATER SHOULDN’T CONDUCT ELECTRICITY Water DOES conduct electricity For water to conduct, there MUST be charged particles The charged particles present are IONS