cm3 - Properties of acids Properties Taste Sour (kids,...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Properties of acids Properties Taste Sour (kids, don’t try this at home). s Conduct electricity. s Some are strong, some are weak electrolytes. s React with metals to form hydrogen gas. s Change indicators (litmus red). s React with hydroxides to form water and a salt. s Properties of bases Properties React with acids to form water and a salt. s Taste bitter. s Feel slippery (Don’t try this either). s Can be strong or weak electrolytes. s Change indicators (litmus blue). s Types of Acids and Bases Types Several Definitions Arrhenius Definition Arrhenius Acids produce hydrogen ions in aqueous solution. s Bases produce hydroxide ions when dissolved in water. s Limits to aqueous solutions. s Only one kind of base. s s NH3 ammonia could not be an Arrhenius base. Polyprotic Acids Polyprotic s Some compounds have more than 1 ionizable hydrogen. HNO3 nitric acid ­ monoprotic H2SO4 sulfuric acid ­ diprotic ­ 2 H+ H3PO4 phosphoric acid ­ triprotic ­ 3 H+ s s s Bronsted-Lowry Definitions Bronsted-Lowry An acid is a proton (H+) donor and a base is a proton acceptor. s Acids and bases always come in pairs. s HCl is an acid. s When it dissolves in water it gives its proton to water. s s s HCl(g) + H2O(l) H3O+ + Cl­ Water is a base ­makes hydronium ion. Come in Pairs Come s s s General equation HA(aq) + H2O(l) H3O+(aq) + A­(aq) Acid + Base Conjugate acid + Conjugate base s This is an equilibrium. s s B(aq) + H2O(l) Base + Acid BH+(aq) + OH­(aq) Conjugate acid + Conjugate base s NH (aq)+H O(l) NH +(aq)+OH­(aq) Water Water s s s Water ionizes­ falls apart into ions. H2O → H+ + OH­ Called the self ionization of water. s Only a small amount. [H+ ] = [OH­] = 1 x 10­7M s A neutral solution. s In water Kw = [H+ ] x [OH­] = 1 x 10­14 s Kw is called the ion product constant. s Ion Product Constant Ion s s H2O H+ + OH­ H Kw is constant in every aqueous. solution [H+] x [OH­] = 1 x 10­14M2 If [H+] > 10­7 then [OH­] < 10­7 s s If [H+] < 10­7 then [OH­] > 10­7 s If we know one, we can determine the other. s If [H+] > 10­7 acidic [OH­] < 10­7 s If [H+] < 10­7 basic [OH­] > 10­7 Logarithms Logarithms Powers of ten. s A shorthand for big, or small numbers. s s s s s pH = ­log[H+] in neutral pH = ­ log(1 x 10­7) = 7 in acidic solution [H+] > 10­7 pH < ­log(10­7) s pH < 7 s in base pH > 7 pH and pOH pH s s pOH = ­ log [OH­] [H+] x [OH­] = 1 x 10­14M2 s pH+pOH = 14 [H+] 10 10­ 01 0 1 Acidic 14 13 10­ 10­ 10­ 10­ 10­ pH 9 11 3 5 7 3 11 79 Neutral 9 75 5 11 3 10­ 10­ 13 14 13 14 Basic 1 0 10­14 10­13 10­11 pOH 10­9Basic 10­5 10­3 10­1 100 10­7 [OH­] How Strong How Strength Strength Strong acids and bases are strong electrolytes s They fall apart completely. s Weak acids don’t completely ionize. s Concentrated­ much dissolved. s Strong forms many ions when dissolved. s Mg(OH) is a strong base­ it falls completely 2 apart when dissolved. s Not much dissolves. s s s Ionization is reversible. Measuring strength Measuring HA H+ + A­ s makes an equilibrium. s Equilibrium constant for an acid(acid dissociation constant.) Ka = [H+ ][A­ ] [HA] s Stronger acid­ more products. s s larger Ka (pg 450) What about bases? What s s s Strong bases dissociate completely. B + H2O BH+ + OH­ Base dissociation constant. s K = [BH+ ][OH­] b [B] s We can ignore the water because it’s concentration doesn’t change. s Stronger base more dissociated. s Larger K b. Practice Practice s s Write the expression for HNO2 Write the Kb for NH3 Neutralization reactions Neutralization Neutralization Reactions s Acid + Base → Salt + water s Salt = an ionic compound s Water = HOH s HNO + KOH → 3 s HCl + Mg(OH) → 2 sH 2 SO4 + NaOH → s Really just double replacement. Reactions Happen in Moles s How many moles of HNO are need to 3 neutralize 0.86 moles of KOH? s How many moles of HCl are needed to neutralize 3.5 moles of Mg(OH)2 ? Usually happen in solutions Usually s If it takes 87 mL of an HCl solution to neutralize 0.67 moles of Mg(OH)2 what is the concentration of the HCl solution? s If it takes 58 mL of an H SO4 solution to neutralize 0.34 moles of NaOH what is the concentration of the H2SO4 solution? 2 Titration Titration Determining an unknown Titration Titration When you add the same number of moles of acid and base, the solution is neutral. s By measuring the amount of a base added you can determine the concentration of the acid. s If you know the concentration of the base. s This is a titration. s Titration equations Titration s s Ma x Va x # of H+ = Mb x Vb x # of OH­ really moles of H+= moles of OH­ More Practice More s If it takes 45 mL of a 1.0 M NaOH solution to neutralize 57 mL of HCl, what is the concentration of the HCl ? If it takes 67 mL of 0.500 M H2SO4 to neutralize 15mL of Al(OH)3 what was the concentration of the Al(OH)3 ? s s How much of a 0.275 M HCl will be needed to neutralize 25mL of .154 M NaOH? Solubility Solubility Dissolving stuff is an equilibrium s CaCl2(s) Ca+2 (aq) + 2 Cl­ (aq) s You can write and equilibrium constant for dissolving s K = [Ca+2] [Cl­]2 eq [CaCl2] s The concentration of a solid does not change, so we can combine it with Keq s s Ksp = [Ca+2] [Cl­]2 Solubility Solubility s s s Ksp is called the solubility product constant The more soluble a solid is the greater Ksp Used for slightly soluble salts. s Can tell if a precipitate will form. s Do the math s If the answer is bigger than the Ksp it will form s If not, it will all stay dissolved ...
View Full Document

This document was uploaded on 02/06/2011.

Ask a homework question - tutors are online