# Go over Ch 20-21 Test Summary of this week Questions over the reading Discussion / explanation Homework.

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Go over Ch 20-21 Test Summary of this week Questions over the reading Discussion / explanation Homework

1. Write a balanced equation for the following neutralization reactions: a. HCl + NaOH b. HCl + NH 3 c. HC 2 H 3 O 2 + NaOH Neutralization reactions produce a salt and water. The salt that is produced can either make the solution acidic, basic or neutral.

Weak Conjugates - do NOT hydrolyze in water Group 1 and 2 ions Conj base of strong monoprotic acids EX: HNO 3 + H 2 O NO 3 - + H 3 O + will cause the solution to be neutral Strong Conjugates – will hydrolyze in water all other ions will either cause the solution to be acidic or basic

Strong acid + strong base neutral HCl + NaOH H 2 O + NaCl When NaCl is in solution, it ionizes: NaCl Na + + Cl - weak conj weak conj Because both ions are weak, the solution will not want to donate or accept any H +, so it is neutral

Strong acid + weak base acidic HCl + NH 3 NH 4 + + Cl - strong conj weak conj Strong conj will react with water: NH 4 + + H 2 O NH 3 + H 3 O + * Positive ions act as acids (donate H+) * If the solution produces an H + or H 3 O + ion, it is acidic

Strong base + weak acid basic NaOH + HC 2 H 3 O 2 H 2 O + NaC 2 H 3 O 2 When NaC 2 H 3 O 2 is in solution, it ionizes: NaC 2 H 3 O 2 Na + + C 2 H 3 O 2 – weak conj strong conj Strong conj will react with water: C 2 H 3 O 2 – + H 2 O HC 2 H 3 O 2 + OH - * Negative ions act as bases (accept H+) * If the solution produces an OH - ion it is basic

Will this salt produce a solution that is slightly acidic, basic or neutral? NaHCO 3

Will the following salts produce a solution that is slightly acidic, basic or neutral? NH 4 NO 3 KCl Na 2 CO 3 Na 2 SO 4 NH 4 Cl

Will the following salts produce a solution that is slightly acidic, basic or neutral? NH 4 NO 3 - acidic KCl - neutral Na 2 CO 3 - basic Na 2 SO 4 - neutral NH 4 Cl - acidic

An aqueous solution that can absorb small amounts of acid or base without a significant change in pH Composed of a weak acid OR a weak base AND a salt of that acid or base Must have 2 components: One for absorbing acid One for absorbing base

Weak acid and its conj base (salt) (acetic acid and sodium acetate) HC 2 H 3 O 2 + H 2 o C 2 H 3 O 2 - + H 3 O + NaC 2 H 3 O 2 Na + + C 2 H 3 O 2 - When a small amt of acid (H + ) is added, the C 2 H 3 O 2 - ion absorbs the H + ions, which produces more HC 2 H 3 O 2. Because HC 2 H 3 O 2 is a weak acid and does not ionize very much in water, the pH will not change When a small amt of base (OH - ) is added, it reacts with the HC 2 H 3 O 2 to produce water.

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