CHM 2046 Lecture Notes - Solubility Equilibrium, Rice Chart

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blushsheep617

16 Apr 2014

School

University of Florida

Department

Chemistry

Course

CHM 2046

Professor

Christou

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Document Summary

The effect of ph on the solubility of zn(oh)2. Some solids that are only weakly soluble in pure water become much more soluble in an acidic solution (ph < 7). An obvious example are compounds that produce oh- ions when dissolved, such as metal hydroxides. Zn(oh)2 (s) zn2+ (aq) + 2 oh- (aq) We have already seen that in increase in the [h3o+] concentration reduces the [oh-], since kw = Thus, in order to maintain the solubility product ksp, the concentration of [zn2+] must increase, leading to the increased solubility of the solid. Solution: (1) set up an ice table, and solve for the solubility (x) of zn(oh)2 (s). Zn(oh)2 (s) zn2+ (aq) + 2 oh- (aq) (solid) Therefore, solubility (x) = 2. 2 x 10-6 m. (2) there are actually two equilibria to take into account. The one above for zn(oh)2 and the usual one for water: 2h2o (l) h3o+ (aq) + oh- (aq)

Related Questions

6 What is the molar solubility of cadmium hydroxide,Cd(OH)₂ in pure water at 25 ^oC? Note thatK_SP for Cd(OH)₂ is 5.3 x 10^-15 at25 ^oC

IMPORTANT: Enter your answer in scientific notation to 2significant figures. For example, if your answer is 9.8765432 x10^-1, you should enter 9.9E-1. Failure to adhere to thisformat may cause WebCT to mark your answer as incorrect.

7 In the previous problem, you calculated the solubility ofCd(OH)₂ in mol/L. What is this solubility in mg/L? Notethe following atomic weights: Cd 112.411 O 15.9994 H 1.0079

IMPORTANT: Enter your answer in floating point to 1 decimal place.For example, if your answer is 9.876543210, you should enter 9.9.Failure to adhere to this format may cause WebCT to mark youranswer as incorrect <?xml:namespace prefix = o ns ="urn:schemas-microsoft-com:office:office" /?>

8 In the previous two problems, you looked at the solubility ofCd(OH)₂ in pure water. Now consider a 0.50 MCd(NO₃)₂. Cadmium nitrate,Cd(NO₃)₂ is a freely soluble salt. When a0.50 M Cd(NO₃)₂ is prepared, the cadmiumnitrate dissolves without establishing an equilibrium:

Cd(NO₃)₂(s) ==========>Cd²⁺(aq) + 2NO₃^-(aq)

In a 0.50 M Cd(NO₃)₂ solution, theconcentration of Cd²⁺ will be 0.50 mol/L. When theCd(OH)₂ is dissolved in this solution, it establishesits usual equilibrium between the solid and the ions insolution:

Cd(OH)₂(s) <----------> Cd²⁺(aq) +2OH^-(aq)

However, the presence of Cd(NO₃)₂ in thissolution means there will be Cd²⁺ ions in solution evenbefore the Cd(OH)₂ dissolves. What is the molarsolubility of Cd(OH)₂ in a 0.50 MCd(NO₃)₂ solutioN

9. In problem 6, you calculated the molar solubility ofCd(OH)₂ in distilled water, and in problem 8, youcalculated the molar solubility of Cd(OH)₂ in a 0.50 MCd(NO₃)₂ solution. Now consider a 0.50 M NaClsolution. Sodium chloride, NaCl is a freely soluble salt. When a0.50 M NaCl solution is prepared, the NaCl dissolves withoutestablishing an equilibrium:

NaCl(s) ==========> Na⁺(aq) +Cl^-(aq)

In a 0.50 M NaCl solution, the concentration of Cl^- willbe 0.50 mol/L. When the Cd(OH)₂ is dissolved in thissolution, it establishes its usual equilibrium between the solidand the ions in solution:

Cd(OH)₂(s) <----------> Cd²⁺(aq) +2OH^-(aq)

The Cd²⁺ ions then react with the Cl^- ionsfrom NaCl to form a complex ion:

Cd²⁺(aq) + 4Cl^-(aq) <---------->[CdCl₄]^2-(aq)

Note that the formation constant for[CdCl₄]^2-, K_f is 1.0 x10⁴.

IMPORTANT: Enter your answer in scientific notation to 2significant figures. For example, if your answer is 9.8765432 x10^-1, you should enter 9.9E-1.

QUESTION 1

Which of the following substances is most acidic?

		Cowâs milk - pH 6.6
		Apple juice - pH 3.0
		Tomato juice - pH 4.5
		Distilled water - pH 7.0

2 points

QUESTION 2

A buffer is a substance that converts:

Alkaline solutions to neutral solutions.

Acidic solutions to alkaline solutions.

Strong bases or acids to weak bases or acids.

Acidic solutions to neutral solutions.

QUESTION 3

How does a solution of pH 7 compare to a solution of pH 10?

		pH 7 has more OH^- ions
		pH 7 is more basic
		pH 7 has a higher pH
		pH 7 has more H⁺ ions

2 points

QUESTION 4

According to the Arrhenius Theory of acids and bases, a base is:

A substance that decrease the amount of hydroxide ions present.

A substance that increases the amount of hydroxide ions present when it is dissolved in water.

A substance that increase the amount of hydrogen ions present.

A substance that increases the amount of hydrogen ions present when it is dissolved in water.

QUESTION 5

Which of the following are true regarding acid-base titrations?

		They are used to determine the concentration of an unknown acid or base.
		The acid or the base must be a standard solution with a known concentration
		The standard solution is titrated into the chemical with the unknown concentration.
		All of the above are true regarding acid-base titrations.

2 points

QUESTION 6

Which of the following is not an example of a neutralization reaction?

HCl + NaOH NaCl +H₂O

2 NaOH + H₂CO₃ Na₂CO₃ +2 H₂O

H₂SO₄ + 2 NH₄OH (NH₄)₂SO₄ + 2 H₂O

2 AgNO₃ + Zn 2Ag +Zn(NO₃)₂

QUESTION 7

Which acid base theory defines an acid as a proton donor and a base as a proton acceptor?

		Arrhenius Theory
		Bronsted-Lowery Theory
		Conjugate Pairs Theory
		Lewis Theory

2 points

QUESTION 8

The Arrhenius Theory states that acid-base reactions create a solution composed of a water and a salt. This is because mixing an acidic and basic solution together yields:

A neutral solution

A solution with a pH at or near 7

Both A and B are correct

QUESTION 9

Which of the following correctly defines a standard solution?

		A solution which always has the same molecular geometry.
		A solution in which the concentration is precisely known.
		A solution in which the volume is precisely known.
		A solution which always has different levels of solutes and solvents.

2 points

QUESTION 10

Acids naturally present in food are generally safe to eat because they are usually:

		Concentrated
		Dilute
		Weak
		Strong

None of the above are correct

THIS IS A FOUR PART QUESTION. HELP NEEDED. THANK YOU VERY MUCH.

a) Using the solubility of Ca(IO3) 2 that you determined in pure water, calculate the value of K sp using only concentrations, that is assuming that all activity coefficients are 1.0. Use 3 sig figs. Solubility of Ca(IO3)2 in Water: 0.00828 mols/L

b) Using the solubility of Ca(IO3)2 that you determined in 0.01M KIO3 as a solvent (the answer from part a), calculate the value of Ksp using only concentrations, that is assuming that all activity coefficients are 1.0. Solubility of Ca(IO3)2 = 0.00327

c) The next few questions will incorporate activity effects into the calculation of Ksp for Ca(IO3)2 using your data from the saturated solution of Ca(IO3)2 in pure water.To do so, we must first know the ionic strength of the solutions. Use your value of the solubility of Ca(IO3)2 in pure water to calculate the ionic strength of that solution.

d) Using the value of the ionic strength of a saturated solution of Ca(IO3)2 in pure water, use TABLE I under the solubility product experiment from the laboratory manual, and enter the activity coefficient for Ca2+ ions listed there at the ionic strength closest to that of the saturated solution of Ca(IO3)2 in pure water. If your ionic strength happens to lie exactly between two values in TABLE I, then use the activity coefficient for the higher ionic strength.

If you need any other information, please let me know.

CHM 2046 Lecture Notes - Solubility Equilibrium, Rice Chart

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