Conjugate acids and bases

Different definitions of acids and bases Acids are proton donors (Brønsted Lowry definition)Acids are proton donors (Brønsted Lowry definition) –they generate H 3 O + in water (Arrhenius definition) Bases are proton acceptorsBases are proton acceptors –they generate OH - in water which is an acid/base?which is an acid/base? HF + H 2 O  H 3 O + + F -HF + H 2 O  H 3 O + + F - NaHCO 3 + H 2 O  Na + +H 2 O + CO 2 + OH -NaHCO 3 + H 2 O  Na + +H 2 O + CO 2 + OH -

Follow the proton HF + H 2 O  H 3 O + + F -HF + H 2 O  H 3 O + + F - NaHCO 3 + H 2 O  Na + + H 2 O+CO 2 +OH -NaHCO 3 + H 2 O  Na + + H 2 O+CO 2 +OH - Joining equilibrium to acid base…What about the reverse reaction?Joining equilibrium to acid base…What about the reverse reaction? H+H+ H+H+ H+H+ H+H+

Conjugate acids and bases When you run the reverse reaction you find the products are also acids and bases. The acids and bases that are formed are called conjugate acids or basesWhen you run the reverse reaction you find the products are also acids and bases. The acids and bases that are formed are called conjugate acids or bases H 2 O + HF  H 3 O + + F -H 2 O + HF  H 3 O + + F - base acid conjugate acid conjugate basebase acid conjugate acid conjugate base NaHCO 3 + H 2 O  Na + +H 2 O + CO 2 +OH -NaHCO 3 + H 2 O  Na + +H 2 O + CO 2 +OH - base acid CA CBbase acid CA CB

Label Acid, Base, Conjugate Acid, Conjugate Base HClO 3 + H 2 O  ClO 3 - +H 3 O +HClO 3 + H 2 O  ClO 3 - +H 3 O + A B CB CA A B CB CA ClO - + H 2 O  HClO + OH -ClO - + H 2 O  HClO + OH - B A CA CB B A CA CB HSO H 2 O  SO H 3 O +HSO H 2 O  SO H 3 O + A B CB CA A B CB CA LiOH + H 2 O  Li + + H 2 O + OH -LiOH + H 2 O  Li + + H 2 O + OH - B A CA CB B A CA CB

Conjugate acids and bases … Conjugate acids and bases determine if an acid or base is strong or weak.Conjugate acids and bases determine if an acid or base is strong or weak. If the conjugate acid/base readily reacts to run the reverse reaction it is a weak acid/base.If the conjugate acid/base readily reacts to run the reverse reaction it is a weak acid/base. If it does not react in the reverse reaction the acid or base is strong.If it does not react in the reverse reaction the acid or base is strong.

Strong acids Acidformula Nitric AcidHNO 3 Sulfuric AcidH 2 SO 4 Hydrochloric acid HCl

Strong Bases NameFormulaNameFormula Sodium Hydroxide NaOHCalcium Hydroxide Ca(OH) 2 Potassium Hydroxide KOHStrontium Hydroxide Sr(OH) 2 Barium Hydroxide Ba(OH) 2 these make a lightning bolt on the periodic table!

More with conjugate acids/bases H 2 SO 4 + H 2 O  H 3 O + + HSO 4 -H 2 SO 4 + H 2 O  H 3 O + + HSO 4 - Sulfuric acid is a strong acid so its conjugate base, HSO 4 -, will not run the reverse reaction.Sulfuric acid is a strong acid so its conjugate base, HSO 4 -, will not run the reverse reaction. HSO 4 - is actually an acid in water.HSO 4 - is actually an acid in water. HSO H 2 O  H 3 O + + SO 4 2-HSO H 2 O  H 3 O + + SO 4 2- SO 4 2- will run the reverse reaction, so it is a weak acidSO 4 2- will run the reverse reaction, so it is a weak acid

Other weak acids and bases Weak AcidsWeak Acids –Acetic Acid (vinegar) –Citric Acid –Ascorbic Acid (vitamin C) –Boric Acid –Carbonic Acid Weak BasesWeak Bases –Sodium Bicarbonate –Ammonia –Sodium Hypochlorite (bleach)

Danger!!! Strong and Weak acids and bases do NOT necessarily tell you how dangerous they are.Strong and Weak acids and bases do NOT necessarily tell you how dangerous they are. Concentration is the most important factor for determining danger.Concentration is the most important factor for determining danger. Ammonia is a weak base, if it is highly concentrated it can burn you.Ammonia is a weak base, if it is highly concentrated it can burn you. Dilute hydrochloric acid (less than 1 M) is not particularly dangerousDilute hydrochloric acid (less than 1 M) is not particularly dangerous

What is water Water is either an acid or base depending on the situation.Water is either an acid or base depending on the situation. Anything that is either an acid or a base is called amphoteric.Anything that is either an acid or a base is called amphoteric. Several things are amphoteric, like parts of you.Several things are amphoteric, like parts of you.

Donating Protons Hydrochloric acid (HCl) can donate 1 proton, so it is called a monoprotic acid.Hydrochloric acid (HCl) can donate 1 proton, so it is called a monoprotic acid. Sulfuric acid (H 2 SO 4 ) can donate 2 protons, so it is called a diprotic acid.Sulfuric acid (H 2 SO 4 ) can donate 2 protons, so it is called a diprotic acid. Phosphoric acid (H 3 PO 4 ) can donate 3 protons, so it is called a triprotic acid.Phosphoric acid (H 3 PO 4 ) can donate 3 protons, so it is called a triprotic acid.