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Acid & Base

Chapter 10. Acid & Base. Prepared By, Mrs Yap- Wong Fui Yen . Handle acid with care!. Some everyday things that contain acids. In fact, we even have acid in our stomach!!!. What properties do acids have in common?. Sharp and sour taste. Corrosive pH less than 7.

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Acid & Base

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  1. Chapter 10 Acid & Base Prepared By, Mrs Yap- Wong Fui Yen

  2. Handle acid with care!

  3. Some everyday things that contain acids

  4. In fact, we even have acid in our stomach!!!

  5. What properties do acids have in common? • Sharp and sour taste. • Corrosive • pH less than 7

  6. What is the meaning of acids? • An acid is a substance that produces ___________ when it dissolve in water. hydrogen ions,H+

  7. without water water • Acids only produce hydrogen ions in water. • Acids only show the properties of acids when they are dissolved in water.

  8. This is because acids ionise in water. add water • It is the hydrogen ions which are responsible for acidic properties.

  9. Experiment I: The pH Scale

  10. What is the pH Scale? • A scale which measures the degree of acidity or alkalinity of an aqueous solution. • Ranges from 0 – 14.

  11. pH = 0 1 2 Increasing Acidity 3 Orange Juice 4 Acid Rain 5 Soft drink, Black Coffee 6 Urine Neutral 7 8 Sea water 9 Baking Soda Increasing Alkalinity 10 Soap 11 Ammonia 12 Detergent 13 pH = 14 Sodium hydroxide pH of some common substances: HCL Lemon Juice , Vinegar “Pure water”

  12. pH = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 pH = 14 • Solutions of pH less than 7 is acidic. • The smaller the pH, the more acidic. HCl Soft drink • Solution of pH 7 is neutral “Pure water” • Solutions of pH greater than 7 is alkaline. • The bigger the pH, the more alkaline. Detergent Sodium hydroxide

  13. Common pH indicators: • Universal Indicator • Litmus paper • Phenolphthalein • Methyl orange • Different colours are observed in solutions depending whether it is:- • acidic • alkaline.

  14. Type of Reactions of Acids: ACIDS reacts with 1. Metals 3. Metal Oxides And Hydroxides (Neutralisation) 2. Carbonates

  15. Reaction 1: Acid with metals Acid Metal + Salt  + Hydrogen Magnesium ribbon Dilute hydrochloric acid (HCl)

  16. Example: Magnesium + hydrochloric  magnesium chloride acid + hydrogen Mg + 2HCl ----> MgCl2 + H2 Test: Use a burning/lighted splinter to test hydrogen gas. Result: A ‘pop’ sound is heard

  17. Reaction 2: Acid with carbonate Acid carbonate salt carbon dioxide +  + + water

  18. Example (2a): Word Equation: calcium + hydrochloric  calcium chloride carbonate acid + carbon dioxide + water Chemical Equation: CaCO3 + 2HCl  CaCl2 + CO2 + H2O

  19. Reaction 3: Acid with metal oxide/ hydroxide Metal oxide /hydroxide Acid +  salt + water copper(II) oxide + hydrochloric  copper(II) cloride acid + water CuO + 2HCl ------> CuCl2 + H2O This reaction is also known as “neutralisation”.

  20. Summary (a)Acid and Metal metal + acid  salt + hydrogen (b)Acid and Carbonate carbonate + acid  salt + water + carbon dioxide (c)Acid and Metal Oxide/ Hydroxide (Neutralisation) acid + base  salt + water

  21. Not done yet! So,what are the common alkalis used in our daily life?

  22. Some everyday things that contain alkali

  23. Perming solutions contain alkali which makes hair curly

  24. Baking powder is alkaline

  25. What properties do bases have in common? • pH >7 • Bitter taste. • Soapy feeling to the skin.

  26. What is the meaning of bases? • solution of hydroxide ions,OH-are produced when bases dissolve in water. NaOH  Na+ + OH- Ca(OH)2 Ca2+ + 2OH –

  27. Is base similar to alkaline? • Most bases are insoluble in water. • Bases that dissolve in water/ soluble are called alkalis.

  28. Bases reactions BASES reacts with 1. Acids (Neutralisation) 2. Ammonium Salts

  29. 1. Neutralisation reaction Bases reacts with an acid to produce a salt and water ACID + BASE --> SALT + WATER HCl + NaOH -----> NaCl + H2O

  30. Write a word and symbol equation when sulphuric acid react with sodium hydroxide? H2SO4 + 2NaOH  Na2SO4 + 2H2O

  31. 3. Alkali reacts with an ammonium salt. Ammonium + sodium  sodium chloride chloride hydroxide + water + ammonia gas NH4Cl + NaOH --> NaCl + H2O + NH3 • Ammonia gasis produced.

  32. Importance of pH: • pH of soil • pH of tank • pH of food

  33. pH & Agriculture • pH of soil • Excess acid in the soil can be neutralised by adding calcium hydroxide (slaked lime). • Farmers spread calcium hydroxide powder over their fields to neutralise acids.

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