Regents Chemistry Exam August 2022
During a laboratory activity appropriate safety equipment is used and safety procedures are followed. A student tests samples of four different metals using 0.20 M aqueous metal ion solutions of the same four metals. The student uses a 24-well plate as the reaction container for the different metal and solution combinations. Before placing a metal strip in each solution, the student cleans the surface of the metal strip with sandpaper. The 24-well plate diagram below shows the setup and results of the investigation. In each vertical column, the metal strips are all the same metal. For each horizontal row, all of the solutions contain the same type of metal ion.
78. Using the results of the student’s investigation, state evidence that zinc metal is more active than copper metal. 
Let's take a look at the zinc metal Zn(s) and copper metal Cu(s) solution columns. We can see that zinc appears dark in the solution with iron ion and copper ion. Copper metal, on the other hand, does not appear dark with any of the ions. Therefore iron is more active than copper.
79. Compare the number of electrons lost by the Mg(s) placed in the Zn2+(aq) solution to the number of electrons gained by the Zn2+(aq). 
Mg becomes Mg2+, which means it loses two electrons (electrons are negative). Zn2+ gains two electrons to become Zn.
Answer: The number of electrons lost by magnesium is equal to the number of electrons gained by zinc ion.
80. Write a balanced, half-reaction equation for the reduction of the copper ions. 
What happens during reduction? LEO said GER. LEO (loss of electrons is oxidation). GER (gain of electrons is reduction.
Copper ion is Cu2+ and it must gain 2 electrons to become Cu.
Please always put a negative sign next to an electron symbol.
81. State why the student was instructed to clean the surface of the metal strips with sandpaper before placing each strip into an aqueous metal ion solution. 
Cleaning the surface of each metal strip with sandpaper removes tarnish and provides a fresh metal surface.