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Acids and Bases and Salts – revisited 

Acids and Bases and Salts – revisited . What is an Acid ?. A substance which reacts with a base to form salt and water . Sour taste pH less than 7 There are two types of acids ; Organic acids – which contain carbon Mineral acids – which contain inorganic compounds.

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Acids and Bases and Salts – revisited 

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  1. Acidsand Bases andSalts – revisited

  2. Whatis an Acid? • A substancewhichreactswith a baseto form saltandwater. • Sour taste • pH lessthan 7 • Therearetwotypesofacids; • Organicacids – whichcontaincarbon • Mineral acids – whichcontaininorganiccompounds.

  3. Organicand Mineral Acids Organic Mineral Carbonicacid H2CO3 In fizzydrinks Weak HydrochloricacidHCl Oven cleaner Dilute form in stomach Nitricacid HNO3 Ferlilisersand explosives Sulfuricacid H2SO4 Car batteries, paintsanddetergents Strong andcorrosive • Ethanoicacid CH3COOH • In vinegar • Methanoicacid HCOOH • In antandnettlestings • Citricacid C6H8O7 • In lemons, oranges etc. • Present in animaland plant material. • weak

  4. Indicators • Litmus (plant extractfromlichens) • Neutral solutions – purple • Acidicsolutions – red • Basic solutions – blue Memory tip R e acid /base l u e Litmuspaper must alwaysbedampwhenused....whyisthis?

  5. Other indicators • Useyourbookstocompletethefollowingchart.

  6. Universal Indicator • Mixtureofindicatordyes. • Gives a rangeofcolours.

  7. pH Scale • DanishchemistSørenSørensenworked in theCarlsbergbreweriesand was interested in checkingtheacidityofbeer. • He developedthe pH scale. • pH canbemeasuredwith universal indicatorand also with a pH meter.

  8. pH scaleandexamples • Useyourbookstohelpyoufill in thefollowingchart.

  9. Activity • Answerquestions 1 – 7 on page 140

  10. Acidand Alkali Solutions • The importanceofions • Bothacidandalkaisolutionsconductelectricitywell. This meansthereis a prsenceofions. • Acidsdissolve in watertoproduce hydrogen ions HClH+ (aq) + Cl- (aq) The term pH istakenfrom „potenz Hydrogen“ – the power ofthe hydrogen ionconcentration.

  11. Alkali Solutions • Alkali dissolve in watertoproducehydroxideions . NaOH Na+ (aq) + OH- (aq)

  12. Activity - Determinetheionsforthefollowingacidsandalkali. Acids Alkalis NaOH KOH • HCl • HNO3

  13. Activity • Answerthequestions on page 141

  14. Metaland Non-Metal Oxides • Read thesection on metaland non-metaloxides on pages 141 and 143. • Whatdoesamphotericmean? • Answerquestion on page 143.

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