addition of ammonia and after addition of HNO,) Silver(1) can form a prec depend
ID: 1051961 • Letter: A
Question
addition of ammonia and after addition of HNO,) Silver(1) can form a prec depending on the concentration of chloride ion present in the solution. a. Write the reaction for the formation of the complex ion and the reaction for the 4. cipitate and/or a complex ion when it is mixed with sodium chloride, formation of the precipitate (2pts). What concentration of Cis required to form a precipitate of AgCl (s) (2 pts)? (Ag.)- b. 0.1M: [NaCI]-1M). Your answer should be listed as a molar concentration. c. What concentration of CI is required to form a complex ion of [AgCl, 1 (aq) whose d. How can you apply this knowledge to the qualitative analysis separation scheme? Discuss e. Use the table of Kp and K, values in your lab manual to provide two other examples concentration is 0.2 M (3pts)? Assume the concentration of IAg'] is 0.1 M. Your a should be listed as a molar concentration. (2pts). where a precipitate and a complex ion might both form (2pts) 5. Consider a solution that contains ammonia and the Ni ion: Use your reasoning from the questions above to explain why the addition of 3M NHs (an) to Ni2 (ag) will precipitate the nickel out of solution. Write the corresponding reaction (3pts). b. If you continue adding ammonia to the above solution the precipitate will disappear. Use b. If you continue adding ammonia to the above solution the precipitate will disappear. a chemical reaction to explain why the precipitate disappears (2pts). 6. Consider the follseraion shemep separation -57 19 SA Solution containing Ag., Pb2+, and Cu2+ Add HNO, so pH-1 Add H2S; Heat ( ) 04 NaCI (aq) ppt of Y and ID of Z Boil solution 2Explanation / Answer
5) (a) The nickel ion will react with ammonia to form precipitate of its hydroxide (Ni(OH)2)
Ni2+(aq) + 2NH3(aq) + 2H2O(l) ---> Ni(OH)2(s) + 2NH4+(aq)
(b) on further addition of ammonia (excess) the precipitate dissolves in ammonia solution to give blue coloured complex which is soluble in water [ [Ni(NH3)6]2+]
The reaction will be
Ni(OH)2(s) + 6NH3(aq) ---> [Ni(NH3)6]2+(aq) + 2OH-(aq)
6) [part c-e]
a) X = Ag+
b) Cu+2 ion will precipitate there after
d) Pb+2: The presence of lead can be confirmed by addition of chromate solution which will give yellow precipitate of lead chromate.
Ag+ : It can be confirmed by adding ammonia to its salt solution which will dissolve the AgCl ppt. The ppt can be reobtained by adding HCl solution to it
Cu+2: On adding conc. ammonia (NH3 (aq) ) initially results in the precipitation of copper hydroxide. However the excess of ammonia redissolves the copper hydroxide due to formation of complex ion, Cu(NH3)42+. [Blue coloured]
e) Ksp of Ag2S = 6 X 10^-51 = [Ag+]2[S-2]
[Ag+] = 0.15 M
minimum concentration of sulphide ion = Ksp / [Ag+]2
[S-2] =6 X 10^-51 / (0.15)2
[S-2] = 2.67 X 10^-48 M
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