For these questions, please include the state in your answers. (For example, (s)
ID: 482657 • Letter: F
Question
For these questions, please include the state in your answers. (For example, (s) for solid) 1. When the Nickel (ll) ion reacts with ammonia, most students notice only a colour change occurring. Can you explain what the reaction is? And what colour they would see? (2 marks) 2. Silver nitrate should have reacted with potassium thiocyanate to form a precipitate. Write the balanced NETIONICEQUATION of this reaction. (1 mark) B. Multi-ion mixtures 1. Suppose that Lebowski student had a solution that may contain any or all of the following cations: Agt, 2+ Ba Ni21 n his UNKNOWN mixture. Lebowski adds HCI to the solution and a 2+ precipitate forms. He then removes the precipitate and adds NH aq to the supernatant until the solution is basic, no solid forms. After making the supernatant basic, K2Cro4 is then added and a precipitate forms. From what you know about how these ions react, which ions are present in Lebowski's unknown? Indicate with a "yes no", or "possibly then explain. (8 marks) a. Was Agt present in the unknown sample? How do you know? b. Was Pb2+ present in the unknown sample? How do you know? c. Was Ba2+ present in the unknown sample How do you know?Explanation / Answer
1. Ni + 6NH3 ----> Ni(NH3)6 ^2+ blue color
----------------------------------------------
AgNO3 + KSCN = AgSCN + KNO3
Net ionic reaction : Ag+ (aq) + SCN- (aq) -----> AgSCN (s)
-------------------------------------------------------
Ag present -----yes
a ppt forms on addition of HCl Ag+ + Cl- ----> AgCl
Pb present -----yes
precipitate forms on addition of k2CrO4
Ba----> Possibly. more information is needed.
Ni----> No, no color change on adding NH3