Aim: How can we determine if an acid or base is strong or weak? QQ: Define acids and bases according to the three different theories. Do Now: Why are you able to consume acetic acid, but HCl burns your throat when it leaves your stomach? Strength of Acids and Bases The strength of an acid/base is measured by the extent to which it dissociates… HA (aq) ⇌ H + (aq) + A-(aq) Write the K eq expression for the generic acid: K a = [H + ] [A-] / [HA] The larger the K a the stronger the acid… Strong Acids HCl H 2 SO 4 HI HNO 3 HBr HClO 4 These acids dissociate completely! Bases also exist at equilibrium: BOH (aq) ⇌ B + (aq) + OH-(aq) K b = [B + ] [OH-] / [BOH] Strong bases (which dissociate completely), are formed when alkali metals combine with hydroxide ions. Practice: Write the equation, K a or K b expression, find value, is it a strong or weak substance?
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