June 2011 Chemistry Regents #77-79

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Questions

Base your answers to questions 77 through 79  on the information below. A student performed a laboratory activity to observe the reaction between aluminum foil and an aqueous copper(II) chloride solution. The reaction is represented by the balanced equation below. 2Al(s) + 3CuCl2(aq) → 3Cu(s) + 2AlCl3(aq) + energy The procedures and corresponding observations for the activities are given below. 77. State one observation that indicates Cu2+ ions became Cu atoms. [1] HIGHLIGHT TO SEE THE ANSWER The solution is no longer blue green or A reddish-brown solid is formed 78. Describe one change in the procedure that would cause the reaction to occur at a faster rate. [1] HIGHLIGHT TO SEE THE ANSWER Heat the solution before adding Al foil increase the concentration of CuCl2 cut the Al into smaller pieces add a catalyst 79.  State one safety procedure the student should perform after completing the laboratory activity. [1] HIGHLIGHT TO SEE THE ANSWER wash hands dispose of chemicals as directed by the teacher look both ways before crossing the street on the way home from the laboratory activity on to Questions 80-82

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