Ch.15 - Acid and Base EquilibriumWorksheetSee all chapters
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Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Calcium acetate (Ca(CH3COO)2) is commonly used as a food additive, especially in candy. What is the pH of a 0.1 M Ca(CH3COO)2 solution at 25 °C

Solution: Calcium acetate (Ca(CH3COO)2) is commonly used as a food additive, especially in candy. What is the pH of a 0.1 M Ca(CH3COO)2 solution at 25 °C

Problem

Calcium acetate (Ca(CH3COO)2) is commonly used as a food additive, especially in candy. What is the pH of a 0.1 M Ca(CH3COO)2 solution at 25 °C

Solution

We´re asked to calculate the pH of a 0.1 M Ca(CH3COO)2 solution at 25 °C.

Calcium acetate is an ionic salt soluble in water. 


In it, Ca(CH3COO)2 dissociates as follows:

Ca(CH3COO)2 Ca2+(aq) + 2 CH3COO-(aq)


The expression of the equilibrium constant K is:

 K=productsreactants


In solution, the acetate ion can react with water by accepting a proton to form acetic acid:

CH3CO2-(aq) + H2O(l)  CH3COOH(aq) + OH-(aq)

Since acetate ion accepts a proton, it is a base according to the Bronsted-Lowry theory.


For a weak base, the equilibrium constant becomes the basic dissociation constant (Kb).

The expression for Kb is:

Kb=AHOH-A-


For the calcium acetate ion reaction, Kb adopts the form of:

Kb=CH3COOHOH-CH3CO2-

Note that each concentration is raised by the stoichiometric coefficient: [CH3COOH], [HO-], and [CH3CO2-] are raised to 1.


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