12. The equilibrium constant for the reaction: AgBr(s) Ag (aq) Br (aq) AgBr(s) A
ID: 480804 • Letter: 1
Question
12. The equilibrium constant for the reaction: AgBr(s) Ag (aq) Br (aq) AgBr(s) Ag+(aq) Br (aq) is the solubility product constant, K 7.7 x 10-13 at 25°C. Calculate AG for the reaction when [Ag+] 1.0 x 102 M and [Brn] 1.0 x 10-3 M. Is the reaction spontaneous or nonspontaneous at these concentrations? A. AG 69.1 kJ, non spontaneous B. AG 97.5 kJ, nonspontaneous C. AG 40.6 kJ, nonspontaneous D. AG 69.1 kJ, spontaneous E. AG 97.5 kJ, spontaneous 13. What is the vapor pressure (in mm Hg)of a solution made by dissolving 64.78 grams of sodium phosphate (Na3PO4) in 378.85 grams of water, H20, at 66 0C.The vapor pressure of pure water at 65 0C is 187.5 mm Hg. A. 187.1 mm Hg B. 186.6 mm Hg C. 184.0 mm H D. 174.4 mm H E. 163.0 mm Hg 14. Given that the normal freezing point of ammonia is -78°C. Predict the signs of AH, AS, and AG for ammonia when it freezes at -80°C and 1 atm. NH301) NH3(s) AH AS AGExplanation / Answer
12]
G=Go+RTln(Q)
delta Go = -RT*lnKsp
Q = [Ag+] [Br-]
delta G = -RT*lnKsp + RT lnQ
T = 298 K
substituting all values
delta G = 40.6 KJ
delta G is postitve so it is non spontaeous reaction
Answer is C
13]
Moles of water = mass/molar mass = 21.0472
Moles of Na3PO4 = mass/Molarmass = 0.395
Pressure of solution = mole fraction of water *Pressure of pure water
P = 21.0472*187.5 / [21.0472+0.395] = 184 mm Hg
Answer is C
14]
liquid to solid ---> delta S decreases [ Delta S means randomness]
delta H ---> -ve [ energy releases]
delta G is negative at low temperatures as the process is exothermic one
Answer is B
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