CHEM 1220 Chapter Notes - Chapter 17: Conjugate Acid, Sodium Hydroxide, Equivalence Point

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periwinklelizard551

9 Apr 2015

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Northeastern University

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Chemistry & Chemical Biology

Course

CHEM 1220

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All

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Chapter # 17: additional aspects of acid-base equilibria. Common-ion effect - the shift in equilibrium caused by the addition of a solute containing an ion in common with the equilibrium mixture. Addition of a common ion suppresses the ionization of a weak acid or a weak base, shifting the equilibrium towards the reactants. Consider the equilibrium reaction of a weak acid, ch3cooh: What happens when you add a strong acid such as hcl to it: because it is a strong acid, hcl ionizes completely in an aqueous solution. Weak base and strong base (strong base) (weak base) Nh3 + h2o oh- + nh4 adds to. Equilibrium shifts toward reactants to form more nh3. Weak acid and their salts (salts dissociate completely in aqueous solutions) Ch3cooh + h2o h3o+ + ch3coo- (weak acid) Equilibrium shifts toward reactants to form more ch3cooh. Buffer solution a solution that resists changes in ph when a small amount of acid or base is added.

Related Questions

The common-ion effect is defined as the shift in an ionic equilibrium produced by the addition of a solute that provides an ion common to the equilibrium. Compare the following two solutions:

Solution 1: 0.100 M C2H4O2
Solution 2: 5mL 0.100 M C2H4O2 + 5mL 0.100 M HCl

The [H3O+] ions from the strong acid in solution 2 force the equilibrium C2H4O2 ? H2O + C2H3O2- almost completely to the left. As a result, the pH is determined by the H3O+ ions from the strong acid. Calculate the pH of Solution 1 (ka = 1.738 x 10-5) and 2 (assume HCl dominate for calculation)

What is the pH level for Solution 1 and Solution 2?

Common Ion Effect

A) Mg(OH)2 is a sparingly soluble compound, in this case a base, with a solubility product, Ksp, of 5.61Ã10â11. It is used to control the pH and provide nutrients in the biological (microbial) treatment of municipal wastewater streams.

Based on the given value of the Ksp, what is the molar solubility of Mg(OH)2 in pure H2O?

Express your answer with the appropriate units.

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molar solubility =

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The common-ion effect and solubility

The solubility of a slightly soluble compound can be greatly affected by the addition of a soluble compound with a common ion, that is, with one of the ions in the added soluble compound being identical to one of the ions of the slightly soluble compound. The general result of the addition of the common ion is to greatly reduce the solubility of the slightly soluble compound. In other words, the addition of the common ion results in a shift in the equilibrium of the slightly soluble compound.

Part B - Calculate the molar solubility in NaOH

Based on the given value of the Ksp, what is the molar solubility of Mg(OH)2 in 0.200 M NaOH?

Express your answer with the appropriate units.

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molar solubility =

Submit

Part C

This question will be shown after you complete previous question(s).

The common-ion effect and buffer systems

A buffer is a mixed solution of a weak acid or base, combined with its conjugate. Note that this can be understood essentially as a common-ion problem: The conjugate is a common ion added to an equilibrium system of a weak acid or base. The addition of the conjugate shifts the equilibrium of the system to relieve the stress of the added concentration of the common ion. In a solution consisting of a weak acid or base, the equilibrium shift also results in a pH shift of the system.

It is the presence of the common ion in the system that results in buffering behavior, because both added H+ or OHâ ions can be neutralized.

Part D

What is the pH change of a 0.290 M solution of citric acid (pKa=4.77) if citrate is added to a concentration of 0.145 M with no change in volume?

Express the difference in pH numerically to two decimal places.

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CHEM 1220 Chapter Notes - Chapter 17: Conjugate Acid, Sodium Hydroxide, Equivalence Point

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