Lab 6 Thermodynamics 1. Write the chemical equation representing the net ionic e

Question

Lab 6 Thermodynamics

1. Write the chemical equation representing the net ionic equation for the precipitation of AgCl resulting from mixing a solution containing Ag+ with a solution containing Cl-.

2. Write the chemical equation corresponding to the formation of 1 mol of AgCl from its element in their standard states. This is the equation for G°f298 for AgCl. (Refer to your thermochemistry chapter for the topic of formation equations.)

3. How do the two equations (in the two previous questions) differ? Briefly explain the difference in their G° calculation.

4. The value of G°f 298 for Mg2+ is –454.8 kJ/mol. The value of G°f 298 for MgCl2·6H2O is -2114.64 kJ/mol.

a. Use these values as well as other thermodynamic data available on the chart supplied in this lab to calculate the free energy change for the reaction under standard conditions, G°rxn.

b. Calculate the free energy change for the reaction G rxn when equal volumes of 0.20 M Mg2+ and 0.20 M Cl- are mixed.

c. Based on your calculations, predict whether or not a precipitate will form.

Lab 6 Thermodynamics REPORT SHEETS DATA    Table 1

Salt/ppt equation

Sample equation provided for first entry only

G°rxn (kJ)

Grxn (kJ)

(hint: Q 1)

Predict whether precipitation will occur

AgCl

Ag+(aq) + Cl-(aq) AgCl(s)

AgI

Ag2SO4

BaCl22H2O

Ba(NO3)2

BaSO4

Na2SO410H2O

CaCl2

CaSO42H2O

PbCl2

273K

PbCl2

298K

PbCl2

373K

Ba(NO3)2

273K

Ba(NO3)2

298K

Ba(NO3)2

373K

Salt/ppt equation

Sample equation provided for first entry only

G°rxn (kJ)

Grxn (kJ)

(hint: Q 1)

Predict whether precipitation will occur

AgCl

Ag+(aq) + Cl-(aq) AgCl(s)

AgI

Ag2SO4

BaCl22H2O

Ba(NO3)2

BaSO4

Na2SO410H2O

CaCl2

CaSO42H2O

PbCl2

273K

PbCl2

298K

PbCl2

373K

Ba(NO3)2

273K

Ba(NO3)2

298K

Ba(NO3)2

373K

Explanation / Answer

1. Write the chemical equation representing the net ionic equation for the precipitation of AgCl resulting from mixing a solution containing Ag+ with a solution containing Cl-.

Molecular equation

AgNO3(aq) + NaCl(aq) --> AgCl(s) + NaNO3(aq)

complete ionic:

Ag+(aq)+ NO3-(aq)  + Na+(aq) + Cl-(aq) --> AgCl(s) + Na+(aq) + NO3-(aq)

net nionic, get rid of spectator ions

Ag+(aq) + Cl-(aq) --> AgCl(s)  

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