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In Part 2 of Lab #12 you will also determine AGdegree for the solid dissolving i

ID: 921945 • Letter: I

Question

In Part 2 of Lab #12 you will also determine AGdegree for the solid dissolving in water. Suppose you use the same solid as in Question #3 (that is, the molar mass is 86.9 g/mol) and obtain the following data: Determine the concentration of the solid. Determine Delta G degree if we assume K = [solid] in the saturated solution. Determine the value of the equilibrium constant, K, if we take into account the volume of water added to the saturated solution. Determine Delta G degree if we take into account the volume of water added to the saturated solution.

Explanation / Answer

1)
here I am assuming that water is not added to solution

number of moles of solid = mass/ molar mass
                                                     = 2.957/86.9
                                                     = 0.034 mol

volume of solution = 5.47 mL = 0.00547 L

concentration of solid = number of moles/ volume
                                              = 0.034 mol / 0.00547
                                              = 6.22 M

2)
K = [Solid]
so,
K = 6.22
T = 25.9 oC = (25.9 + 273) K= 298.9 K

use:
delta G= -R*T*ln K
               = -8.314 * 298.9* ln 6.22
               = -4542 J/mol
               = -4.542 KJ/mol

3)
after water is added
number of moles of solid = mass/ molar mass
                                                     = 2.957/86.9
                                                     = 0.034 mol

concentration of solid = number of moles/ volume
                                              = 0.034 mol / (0.00547+0.00311)
                                              = 3.963 M

K = [Solid]
so,
K = 3.963

4)

T = 25.9 oC = (25.9 + 273) K= 298.9 K

use:
delta G= -R*T*ln K
               = -8.314 * 298.9* ln 3.963
               = - 3421.8 J/mol
               = - 3.422 KJ/mol

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