Tuesday May 26 Objective: Calculate the amount of acid or base needed to neutralize a solution. Checkpoint: – Calculate the [OH-] in a solution that has a pH of – Calculate the pH of a KOH solution that has a concentration of 0.50 M. Homework: – Titrations problems (Wed/Thurs) – Acids/Bases quiz (Wed/Thurs)

Calculate the [OH-] in a solution that has a pH of start end pOH = 14 – 10.4 [OH - ] = 1 x /-10 x pOH = 3.6 [OH - ] = 2.51 x M ( M)

Calculate the pH of a KOH solution that has a concentration of 0.50 M. [KOH] = 0.50 M pOH = 0.30 pOH = -log(0.50) start end pH = 14 – 0.30 pH = 13.70

Think about this: Excess stomach acid, HCl, can cause extreme discomfort and pain. Milk of magnesia, Mg(OH) 2, is often taken to reduce stomach acid. – What products do you think are produced when Mg(OH) 2 and HCl are mixed? – What type of reaction is this?

Think about this: When your car battery leaks acid, you pour baking soda (a base) on it to neutralize the acid. What does it mean to “neutralize something?”

Neutralization Reactions Acid + Base  Salt + Water – Called a neutralization reaction – Requires use of an indicator to identify neutralization point Strong acid (H + ) + Strong base (OH - )  neutral solution (H 2 O) HCl + NaOH  acid base salt water H2OH2O 2HBr + Ba(OH) 2  2 H 2 O acid base salt water + NaCl + BaBr 2

Titration A titration is a procedure in which a solution of known concentration (the standard solution) is used to identify a solution of unknown concentration. If your unknown is an acid, titrate with a strong base of known []. If your unknown is a base, titrate with a strong acid of known [].

Titration Vocabulary The end point of a titration is when the solution just barely changes color The equivalence point is the point where the acid and base exactly react with one another Ideally, the end point should be the same as the equivalence point. An indicator is a compound that changes color when the pH of a solution changes. They are used in titrations to let you know when the equivalence point has been reached.

Titration Visual Aid

Sample Problem 1 How many mL of 0.45 M HCl must be added to 25 mL of 1.00 M KOH to make a neutral solution? 1.Write balanced equation 2.Find mols of known solution 3.Use mol ratio to find mols of unknown 4.Calculate your unknown value. HCl + KOH  H 2 O + KCl 1.00 M = x L x = mol KOH mol HCl 0.45 M = mol x x = 0.45 x x = L = 11.3 mL

Sample Problem 2 If 24.6 mL of a Ca(OH) 2 solution are needed to neutralize 14.2 mL of M HBr, what is the concentration of the Ca(OH) 2 solution? 1.Write balanced equation 2.Find mols of known solution 3.Use mol ratio to find mols of unknown 4.Calculate your unknown value. HBr + Ca(OH) 2  H 2 O + CaBr M = x L x = mol HBr mol Ca(OH) 2 M = mol L M mol HBr x 2 mol HBr 1 mol Ca(OH) 2