ACIDS, BASES SALTS.ppt
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1、ACIDS, BASES & SALTS,Topic 10: ACIDS, BASES & SALTS,2,T E R M S,ACIDS are substances that form hydrogen ions (H+(aq) when dissolved in water egHydrochloric acid HCl gives H+(aq) and Cl-(aq) ions,Sulphuric acid H2SO4 gives 2H+(aq) and SO42- ions Nitric acid HNO3 gives H+(aq) and NO3-(aq) ions. BASES
2、are oxides and hydroxides of metals that react and neutralise acids to form salts and water only. Bases which are soluble in water are called alkalis. Not all bases fit into these categories e.g. ammonia. Alkalis are substances that form hydroxide ions OH-(aq) in water eg Sodium Hydroxide NaOH gives
3、 Na+(aq) and OH-(aq) ions, Calcium Hydroxide Ca(OH)2 gives Ca2+(aq) and 2OH-(aq) ions., 29 1440,Topic 10: ACIDS, BASES & SALTS,3,In acid solutions there are more H+ ions than OH- ions. In alkaline solution there are more OH- ions than H+ ions. Acids that dissociate (ionize) to a large extent are str
4、ong electrolytes and Strong Acids. Acids that dissociate only to a small extent are Weak Acids and weak electrolytes Bases can be strong or weak depending on the extent to which they dissociate and produce OH ions in solution. Most metal hydroxides are strong electrolytes and Strong Bases. Ammonia,
5、NH3, is a weak electrolyte and Weak Base., 29 1440,Topic 10: ACIDS, BASES & SALTS,4,Basicity of Acid,It is the number of ionizable H+ ions present in an acid e.g. HCl is mono basic, it ionizes to produce one H+ ion HCl = H+ + Cl- H2SO4 is Dibasic, It ionizes to produce two H+ ions. H2SO4 = 2H+ + SO4
6、2- H3PO4 is Tribasic, it ionizes to produce three H+ ions. H3PO4 = 3H+ + PO43-, 29 1440,Topic 10: ACIDS, BASES & SALTS,5,Acidity of a Base,It is the ionizable OH- ions present in an alkali. e.g. NaOH is monoacidic NaOH = Na+ + OH- Ca(OH)2 is diacidic Ca(OH)2 = Ca2+ + 2OH-, 29 1440,Topic 10: ACIDS, B
7、ASES & SALTS,6,Common Strong Acids & their Anions, 29 1440,Topic 10: ACIDS, BASES & SALTS,7,Common Weak Acids & their Anions, 29 1440,Naming of Acids,Binary Acids (H+ and a nonmetal) hydro (nonmetal) -ide + ic acid HCl (aq) = hydrochloric acid Ternary Acids (H+ and a polyatomic ion) (polyatomic ion)
8、 -ate +ic acid HNO3 (aq) = nitric acid (polyatomic ion) -ide +ic acid HCN (aq) = cyanic acid (polyatomic ion) -ite +ous acid HNO2 (aq) = nitrous acid, 29 1440,Topic 10: ACIDS, BASES & SALTS,8,Formula Writing of Acids,Acids formulas get written like any other. Write the H+1 first, then figure out wha
9、t the negative ion is based on the name. Cancel out the charges to write the formula. Dont forget the (aq) after itits only an acid if its in water! Carbonic acid: H+1 and CO3-2 = H2CO3 (aq) Chlorous acid: H+1 and ClO2-1 = HClO2 (aq) Hydrobromic acid: H+1 and Br-1 = HBr (aq) Hydronitric acid:, 29 14
10、40,Topic 10: ACIDS, BASES & SALTS,9,Properties of Bases,Bases react with fats to form soap and glycerol. This process is called saponification. Bases have a pH of more than 7. Dilute solutions of bases taste bitter. Bases turn phenolphthalein PINK, litmus BLUE and bromthymol blue BLUE. Bases neutral
11、ize acids. Bases are formed when alkali metals or alkaline earth metals react with water. The words “alkali” and “alkaline” mean “basic”, as opposed to “acidic”., 29 1440,Topic 10: ACIDS, BASES & SALTS,10,Topic 10: ACIDS, BASES & SALTS,Naming of Bases,Bases are named like any ionic compound, the nam
12、e of the metal ion first (with a Roman numeral if necessary) followed by “hydroxide”.,Fe(OH)2 (aq) = iron (II) hydroxide Fe(OH)3 (aq) = iron (III) hydroxide Al(OH)3 (aq) = aluminum hydroxide NH3 (aq) is the same thing as NH4OH:NH3 + H2O NH4OH Also called ammonium hydroxide., 29 1440,11,Topic 10: ACI
13、DS, BASES & SALTS,Formula Writing of Bases,Formula writing of bases is the same as for any ionic formula writing. The charges of the ions have to cancel out. Calcium hydroxide = Ca+2 and OH-1 = Ca(OH)2 (aq) Potassium hydroxide = K+1 and OH-1 = KOH (aq) Lead (II) hydroxide = Pb+2 and OH-1 = Pb(OH)2 (
14、aq) Lead (IV) hydroxide = Pb+4 and OH-1 = Pb(OH)4 (aq) Lithium hydroxide = Copper (II) hydroxide = Magnesium hydroxide =, 29 1440,12,Topic 10: ACIDS, BASES & SALTS,13,Physical Properties of Acids & Bases,ACIDS Acids taste sour (e.g. vinegar, lemon juice). Acids are harmful to living cells. Aqueous s
15、olutions of all acids contain hydrogen ions. Acid turns blue litmus red. Strong acids are corrosive.BASES Alkalis are taste bitter Strong alkalis are corrosive. Aqueous solutions of all alkalis contain hydroxide ion. Alkalis turns red litmus blue. Soapy touch., 29 1440,Topic 10: ACIDS, BASES & SALTS
16、,14,Chemical Properties of Acids,With metals Metals above copper in the reactivity series will react with acids, giving off hydrogen gas, forming a salt. Mg(s) + H2SO4(aq) MgSO4(aq) + H2(g) With bases (metal oxides and hydroxides) The base dissolves in the acid and neutralises it. A salt is formed.H
17、2SO4(aq) + CuO(s) CuSO4(aq) + H2O(l) With metal carbonates With metal carbonates, effervescence occurs, salt, water and carbon dioxide gas is produced.2HCl(aq) + CaCO3(s) CaCl2(s) + H2O(l) + CO2(g), 29 1440,Neutralization,H+1 + OH-1 HOH Acid + Base Water + Salt (double replacement) HCl (aq) + NaOH (
18、aq) HOH (l) + NaCl (aq) H2SO4 (aq) + KOH (aq) 2 HOH (l) + K2SO4 (aq) HBr (aq) + LiOH (aq) H2CrO4 (aq) + NaOH (aq) HNO3 (aq) + Ca(OH)2 (aq) H3PO4 (aq) + Mg(OH)2 (aq) , 29 1440,Topic 10: ACIDS, BASES & SALTS,15,Topic 10: ACIDS, BASES & SALTS,16,Formation of Hydronium ion( H30+).,The hydrogen ion H+(aq
19、) does not exist as such in aqueous solutions. Hydrogen ions combine with water molecules to give a more stable species, the hydronium ion H3O+. HCl(aq) + H2O(l) = H3O+(aq) + Cl-(aq) Acids can contain different numbers of acidic hydrogens, and can yield different numbers of H3O+ ions in solution., 2
20、9 1440,Topic 10: ACIDS, BASES & SALTS,17,USES OF ACIDS,HCl in stomachH2SO4 in car batteries, as drying agentHNO3 in manufacturing of fertilizersEthanoic acid in food industryFatty acids in soap makingAscorbic acid in medicine, 29 1440,Topic 10: ACIDS, BASES & SALTS,18,Chemical Properties of Bases,Ne
21、utralisation. Ammonium salts are decomposed when mixed with a base eg sodium hydroxide. The ammonia is readily detected by its pungent odour (strong smell) and by turning damp red litmus blue. NaOH + NH4Cl = NaCl + H2O + NH3 Ionically: NH4+ + OH- = H2O + NH3 This reaction can be used to prepare ammo
22、nia gas and as a test for an ammonium salt., 29 1440,Topic 10: ACIDS, BASES & SALTS,19,Chemical Properties of Bases,Alkalis are used to produce the insoluble hydroxide precipitates of many metal ions from their soluble salt solutions. 2NaOH(aq) + CuSO4(aq) = Na2SO4(aq) + Cu(OH)2(s)ionically: Cu2+(aq
23、) + 2OH-(aq) = Cu(OH)2(s) This reaction can be used as a simple test to help identify certain metal ions., 29 1440,Topic 10: ACIDS, BASES & SALTS,20,TYPES OF OXIDES,: BASIC OXIDESOn the left and middle of the Periodic Table are the basic metal oxides eg Na2O, MgO, CuO etc They react with acids to fo
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