# Objective/Warm-Up SWBAT distinguish between weak and strong acids and write equilibrium expressions. Name these acids: HBr H 3 P H 2 SiO 3 HNO 2.

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Objective/Warm-Up SWBAT distinguish between weak and strong acids and write equilibrium expressions. Name these acids: HBr H 3 P H 2 SiO 3 HNO 2

Acid/Base Equilibrium General formula for an Acid dissociation reaction: HA + H 2 O ↔ H 3 O + + A - Or: HA ↔ H + + A -

Write the dissociation equation for each of the following acids: HCl HC 2 H 3 O 2 NH 4 + C 6 H 5 NH 3 + H 2 O

Equilibrium Constant HA + H 2 O ↔ H 3 O + + A - HA ↔ H + + A - K a = [H 3 O + ][A - ] or K a = [H + ][A - ] [HA] [HA] Brackets indicate concentration (molarity).

Write the K a equation for each of the following acids: HCl HC 2 H 3 O 2 NH 4 + C 6 H 5 NH 3 + H 2 O

What does Ka tell us? PropertyStrong AcidWeak Acid K a valueK a is largeK a is small Position of equilibrium Far to the right (a lot of dissociation) Far to the left (little dissociation) [H+] compared to original [HA] [H+]≈[HA] o [H+]<<[HA] o Strength of conjugate base A- much weaker than water A- much stronger than water

Figure 14.4 Graphic Representation of the Behavior of Acids of Different Strengths in Aqueous Solution

Same for bases: K b B + H 2 O ↔ HB + + OH - K b = [HB + ][OH - ] [B]

ICE box calculations Calculate the [H+] and [F-] in a 1.00 M solution of HF if the K a is 7.2 x 10 -4. Write K a expression. HF  H+F- Initial Change End

ICE box calculations Calculate the initial concentration of HF in a solution where the pH = 4.7 and the K a is 7.2 x 10 -4. Write K a expression. HF  H+F- Initial Change End

Practice Problems 18-2

Objective/Warm-Up SWBAT solve ICEbox problems for acids and bases. Write dissociation equations and equilibrium expressions for the following acids: HNO 2 H 2 C 2 O 4 HF

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