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TAN, DEANNAH C. MAY 25, 2015 GEN. CHEM. CALCULATIONS ELECTROCHEMISTRY PROBLEM #1: Write a balanced equation to represent the oxidation of iodide ion by permanganate ion in basic solution to yield molecular iodine and manganese oxide MODIFIED PROBLEM #1: Balance the following equation for the reaction in an acidic medium by the half-reaction method: GIVEN: Reaction: REQUIRED: Balanced reaction (in acidic medium) SOLUTION: The two half-reactions are: Oxidation: Reduction: Balancing the half reactions and its charges: Because the reaction takes place in an acidic medium, four molecules are added to the right side to balance the equation. Adding the two half-reaction gives:

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TAN, DEANNAH C.

MAY 25, 2015

GEN. CHEM. CALCULATIONS

ELECTROCHEMISTRY

PROBLEM #1:

Write a balanced equation to represent the oxidation of iodide ion by permanganate ion in basic solution to yield molecular iodine and manganese oxide MODIFIED PROBLEM #1:

Balance the following equation for the reaction in an acidic medium by the half-reaction method:

GIVEN:

Reaction: REQUIRED:

Balanced reaction (in acidic medium)

SOLUTION:The two half-reactions are:

Oxidation: Reduction: Balancing the half reactions and its charges:

Because the reaction takes place in an acidic medium, four molecules are added to the right side to balance the equation.

Adding the two half-reaction gives:

The electrons on both sides cancel, giving the balanced net ionic equation:

PROBLEM #2:

A galvanic cell consists of an electrode in a solution and an electrode in a solution. Calculate the standard emf of this cell at

MODIFIED PROBLEM #2:

What is the standard emf of a galvanic cell made of an electrode in a solution and an electrode in a solution at GIVEN:

REQUIRED:

standard emf of the cell at SOLUTION:

The standard reduction potentials are

Adding and balancing their charges gives

Anode (oxidation):

Cathode (reduction):

Cancelling the electrons on both sides give,

Solving for the emf,

PROBLEM #3:

Predict whether the following reaction would proceed spontaneously as written at Given that and MODIFIED PROBLEM #3:Will the following reaction occur spontaneously at , given that and GIVEN:

REQUIRED:

Will the given reaction occur spontaneously?SOLUTION:The half-cell reactions are:

Anode (oxidation):

Cathode (reduction):

Solving for

Solving for E QUOTE E using Nernsts Equation

The positive value of E shows that the forward reaction is favoured and is therefore a spontaneous reaction.THERMODYNAMICS

PROBLEM #1:Calculate the standard free-energy changes for the following reactions at a) b)

MODIFIED PROBLEM #1:

From the standard free-energy values in Appendix B Calculate the standard free-energy changes for the following reactions at a) b) GIVEN:

a) b)

REQUIRED:

SOLUTION

a)

Using the appropriate values of

b)

Using the appropriate values of

PROBLEM #2:

Calculate the standard entropy change for the following reactions at a) b) MODIFIED PROBLEM #2:

From the standard entropy values in Appendix B, calculate the standard entropy changes for the following reactions at

a)

b)GIVEN:

a)

b)REQUIRED;

SOLUTION:

a)

Using the values of from the table

b)

Using the values of from the table

SOLUBILITY EQUILIBRIA

PROBLEM #1:The solubility of calcium sulfate is found to be Calculate the value of for calcium sulfate.

MODIFIED PROBLEM #1:

The solubility of lead chromate is Calculate the solubility product of this compound.

GIVEN:

REQUIRED:

SOLUTION:

Initial (M):

0

0

Change (M):

-s +s +s

Equilibrium (M):

s

s

The solubility product for is

Calculating the number of moles of dissolved in 1 L of solution

Calculating

PROBLEM #2:

Calculate the solubility of copper (II) hydroxide,, in g/L. (MODIFIED PROBLEM #2:

Calculate the solubility of silver chloride in g/L. GIVEN:

REQUIRED:

solubility of =? (in g/L)

SOLUTION:

Initial (M):

0

0

Change (M):

-s +s +s

Equilibrium (M):

s

s

The solubility product for is

Calculating the molar solubility of

Calculating solubility in g/L

PROBLEM #3:

If 2.00 mL of are added to 1.00 L of, will precipitation occur?

MODIFIED PROBLEM #5:

Exactly 200 mL of are added to exactly 600 mL of. Will a precipitate form?

GIVEN:

REQUIRED:

Will a precipitate form given these conditions?

SOLUTION:

Calculating the number of moles of present in the original 200 mL of solution

Calculating the concentration of in the 800 mL of combined solution

Calculating the number of moles of present in the original 600 mL of solution

Calculating the concentration of in the 800 mL of combined solution

Comparing with

As for,

Therefore,

; since the solution is supersaturated because the value of indicates that the concentrations of ions are too large. Thus, a precipitate will form and that is.

ACIDS AND BASESPROBLEM #1:

The pH of a certain orange juice is 3.33. Calculate the ion concentrationMODIFIED PROBLEM #1:

The pH of rainwater collected in a certain region of the north-eastern United States on a particular day was 5.23. Calculate the ion concentration of the rain waterGIVEN:

pH of rainwater = 5.23REQUIRED:

SOLUTION:

pH is defined as

Calculating

PROBLEM #2:

The ion concentration of a blood sample is. What is the pH of the blood?

MODIFIED PROBLEM #2:

In a solution is. Calculate the pH of the solution.

GIVEN:

=.

REQUIRED:

pH of the solution =?

SOLUTION:

pH is defined as

As for pOH,

Calculating first pOH gives

Solving for pH using the value of pOH obtained gives