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Acids and bases

Acids and bases. Two Sad Jokes. Q: What did the big chimney say to the little chimney? A: You’re too little to smoke! How do you get a kleenex to dance? Put a little boogey in it. . One more sad rhyme…. Little Jimmy took a drink but now he’ll drink no more….

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Acids and bases

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  1. Acids and bases

  2. Two Sad Jokes • Q: What did the big chimney say to the little chimney? A: You’re too little to smoke! • How do you get a kleenex to dance? • Put a little boogey in it.

  3. One more sad rhyme… • Little Jimmy took a drink but now he’ll drink no more…. • For what he thought was H2O, was H2SO4

  4. Acid • In an aqueous solution, acids produce hydrogen H+ ions. • Example: hydrochloric acid, HCl, which is found in our stomachs. In water the acid will produce H+ and Cl- ions. HCl (aq) H+(aq) + Cl- (aq) Source: http://science.widener.edu/svb/molecule/binary.html

  5. Characteristics of an acid • Sour taste; • Can burn the skin; • Conducts electricity; • Reacts with metals to produce hydrogen gas (H2); • Neutralizes a base; • Reacts with carbonate and bicarbonate to produce carbon dioxide gas (CO2).

  6. A few acids • lemons, stomach acid, acid rain, battery acid, vinegar…

  7. Base • In an aqueous solution a base produces hydroxide OH- ions. Example: sodium hydroxide (NaOH). In water this base produces Na+ and OH- ions. NaOH(aq) OH-(aq) + Na+(aq) Source: http://homepage1.nifty.com/scilla/bunsi/naoh/naoh.jpg

  8. Characteristics of a base • Bitter taste; • Slippery texture, can burn skin; • Conducts electricity; • Neutralizes acids; • Reacts with certain metals (like Al) to produce hydrogen gas (H2). • Does not react with carbonates.

  9. A few bases • bleach, baking soda, soap, Windex, tonic water…

  10. Acid or Base? • H2CO3 H+ + CO32- • Ca(OH)2 Ca2+ + OH- • NH3 + H2O NH4+ + OH- • KOH K+ + OH-

  11. pH scale • The pH scale allows us to « quantify » or measure the acidity or the alcalinity of a substance. • The pH scale goes from 0 to 14; 0 is the most acidic, 14 is the most alcaline (basic) and 7 is neutral (distilled water).

  12. pH Scale Source: http://www.mddep.gouv.qc.ca/eau/eco_aqua/lacs_acides/2004/echelle-ph.htm

  13. pH scale Source: http://www.atmosphere.mpg.de/enid/0,55a304092d09/3__Pluies_acides/-_Qu_est-ce_que_c_est__2us.html

  14. Échelle de pH, suite… Source: http://archive.idrc.ca/aquatox/fr/whatsnu/check.html

  15. Tests to determine the acidity or the alcalinity (pH) of a substance • Red and blue litmus paper • Acids turn blue litmus paper red. • Bases turn red litmus paper blue • Neutral substances will not change the colour of red OR blue litmus paper. Source: http://cahm.nbed.nb.ca/Science/science61d.htm

  16. pH Paper • You compare the colour with a given chart • Instead of telling you whether something is an acid or a base it gives you the exact pH. Source: http://escalade.nbed.nb.ca/images/ex15.jpg

  17. Other indicators • Other substances can be used to measure pH such as cabbage juice! Source: http://www.csvt.qc.ca/patriotes/sciences/scp4/dufort/4-2.htm

  18. Neutralization • An acid reacts with a base to produce water and a salt. (a pH of 7 is neutral) Acid + base salt + water Ex: HCl + NaOH NaCl + H2O

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