I know the answers for these questions, I just want to learn why

1-
Use the table to determine which of the following species will convert Cd2+ to Cd.
A. Fe3+
B. Pb2+
C. Zn
D. Co2+
E. Sn

2-
Which of the following salts will form an acidic aqueous solution?
A. NaCl
B. NaCN
C. CaCl2
D. FeCl3
E. NaNO2

Th first one is done with the activity series. Here is a link.

http://www.files.chem.vt.edu/RVGS/ACT/notes/activity_series.html
Here is the way it works. Any METAL in the activity series will displace any metal ION BELOW it in the series. Therefore, the answer must be a metal (only Zn and Sn qualify) and the answer must b a metal ABOVE Cd. Which one is that?

#2. Write the molecular hydrolysis equation for each.
I'll do one or two.
NaCl + HOH ==> NaOH + HCl.
Both NaOH and HCl are strong electrolytes so the salts are neutral.

NaCN + HOH ==> NaOH + HCN
NaOH is a strong base, HCN is a weak acid; therefore, the solution will be basic.

You can take it from here.

1- To determine which species will convert Cd2+ to Cd, we can use the activity series or electrochemical series of metals. This series ranks metals in order of their ability to be oxidized or reduced in a redox reaction. The higher a metal is on the series, the more easily it can be oxidized (lose electrons) or reduced (gain electrons).

In this case, we are interested in the reduction of Cd2+ to Cd, so we need a metal that is higher on the activity series than Cd. Looking at the options:

A. Fe3+: Iron (Fe) is higher than cadmium (Cd) on the activity series, so it can reduce Cd2+ to Cd.

B. Pb2+: Lead (Pb) is lower on the activity series than Cd, so it cannot reduce Cd2+ to Cd.

C. Zn: Zinc (Zn) is higher than Cd on the activity series, so it can reduce Cd2+ to Cd.

D. Co2+: Cobalt (Co) is lower on the activity series than Cd, so it cannot reduce Cd2+ to Cd.

E. Sn: Tin (Sn) is higher than Cd on the activity series, so it can reduce Cd2+ to Cd.

Therefore, the species that will convert Cd2+ to Cd are A. Fe3+, C. Zn, and E. Sn.

2- To determine which salt will form an acidic aqueous solution, we need to consider the ions present in the salt and their behavior in water.

A. NaCl: Sodium chloride consists of Na+ and Cl- ions. Neither of these ions will contribute to acidity or basicity when dissolved in water. Therefore, NaCl will not form an acidic solution.

B. NaCN: Sodium cyanide consists of Na+ and CN- ions. CN- ions can behave as weak bases and can react with water to form OH- ions, making the solution basic. Therefore, NaCN will not form an acidic solution.

C. CaCl2: Calcium chloride consists of Ca2+ and Cl- ions. Neither of these ions will contribute to acidity or basicity when dissolved in water. Therefore, CaCl2 will not form an acidic solution.

D. FeCl3: Iron(III) chloride consists of Fe3+ and Cl- ions. When FeCl3 is dissolved in water, it will hydrolyze to form Fe(H2O)6^3+ and Cl- ions. The hydrolysis of Fe3+ ions in water results in the formation of H+ ions, making the solution acidic. Therefore, FeCl3 will form an acidic solution.

E. NaNO2: Sodium nitrite consists of Na+ and NO2- ions. NO2- ions can behave as weak acids and can contribute H+ ions to the solution, making it acidic. Therefore, NaNO2 will form an acidic solution.

Therefore, the salt that will form an acidic aqueous solution is D. FeCl3 and E. NaNO2.