CCA - Ksp of silver acetate PDF

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CCA - Ksp of Silver acetate

is a low-solubility salt that dissociates partially according to this equilibrium:

AgCH3COOH(s) ↔ Ag+(aq) + CH3COO-(aq) Silber ions undergo a single displacement reaction with copper: 2Ag+(aq) + Cu(s) ↔ 2Ag(s) + Cu2+(aq)

Question: What is the Ksp of silver acetate? Experimental design: A coil of copper wire is placed in a saturated solution of silver acetate for two days. The copper is removed from the solution, cleaned, and its mass measured to determine how much mass was lost. Evidence: The copper wire was coated with a silver-grey layer Volume of saturated lead(II) chloride solution : 1.00 x102 mL Mass loss of copper wire : 0.19 g Analysis: a) Calculate the amount(in moles) of copper that reacted[

/1 mark]

0.19 g =2.99 ∗10− 3 mol 63.546 g /mol b) Calculate the molar concentration of the silver ions(Ag+]) in the saturated silver acetate solution[ marks] +¿ 2Ag+(aq) + Cu(s) ↔ 2Ag(s) + Cu2+(aq): Set the number of mols Ag ¿ as x. x (mol) 2.99 ∗10− 3 mol = 2(mol) 2 mol x=5.98 ∗10− 3 mol −3 n 5.98 ∗ 10 mol =5.98 ∗ 10−2 mol / L C= = 0.1 L v

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c) Determine the acetate ion(CH3COO-) ion concentration in the saturated silver acetate solution. You must show your work or how you get your answer [ /2 marks] AgCH3COOH(s) ↔ Ag+(aq) + CH3COO-(aq) x 5.98*10^-2 mol y 1 1 1 X,y value in both cases are 5.98*10^-2 mol, because the concentration of acetate and the silver ion are calculated based on the molar ratio of the dissolved compound, as well as the cations and anions. As the molar coefficient of each compound are both 1, so as the silver ion is produced, the same ratio of the acetate ion is produced simultaneously. So the amount of acetate produced is the same as the sliver ion produced which is 5.98*10^-2 mol.

d) Write the Ksp expression for AgCH3COOH and calculate it’s value[

/2marks]

AgCH3COOH(s) ↔ Ag+(aq) + CH3COO-(aq) +¿ ¿ 2 −2 2 −3 Ag [ CH 3 COOH − ]=[ x ][ x]= x =(5.98 ∗ 10 ) =3.58 ∗10 K sp=¿

e) Explain why the copper wire was left in the saturated silver acetate solution for two days? [

/1 mark]

Though in the activity series of metal, the copper metal is able to displace silver from the sliver acetate solution. However, the copper metal in the activity series is close to the silver, therefore the reaction speed of the displacement process is slow. So the time of the reaction need to be sufficient enough to let the silver ion have the opportunity to react with the copper atom on the metal. f) The accepted Ksp value for silver acetate is 4.0 x 10-3. Calculate the % error in the Ksp determined from the experiment.[ /2 mark] (note: your error can be positive or negative) % Error=

3.68 ∗10− 3 − 4.0 0 ∗10− 3 =10.6 % 4.0 0 ∗10 −3

g) Suggest two reasonable sources of error[

/2 marks]

In this reaction, the actual Ksp value of the silver acetate is slow compared to the theoretical value which means that less amount of copper is reacted, one of the possible reason is that in during the cleaning process, there are still small amount of silver left on the copper wire which made the actual mass of the copper is larger than the theoretical value. Another possible reason is that during the reaction process, the silver metal is affixed on the copper wire, which formed a coat so that the solution have less area of the solution to make contact with the sliver metal, during the reaction process, the reaction rate will be decreasing during the

process, which resulting the insufficient reaction which made the final amount of product is less than the theoretical value.

Units, significant digits, proper notation[

/2 marks]...