IN AN EXPERIMENT TO STUDY THE SPONTANEITY OF REDOX REACTIONS, A STUDENT PLACED DIFFERENT METALS INTO FIVE SEPERATE TEST TUBES, EACH CONTAINING A DIFFERENT 1.0MOL/L SOLUTION, AS SHOWN BELOW.
TEST TUBE 1- THE METAL IS Zn(s) in a solution of Fe(NO3)2(aq)
Test tube 2- the metal is Co(s) in a solution of Sn(NO3)2(aq)
test tube 3- the metal is Cu(s) in a solution of Cu(NO3)2(aq)
tets tube 4- the metal is Au(s) in a solution of Cu(NO3)2(aq)
test tube 5- the metal is Ag(s) in a solution of HNO3(aq)
test tube 6- the metal is Ni(s) in a solution of AgNO3(aq)
for each test tube, determine which one is a spontaneous reaction and which one is not a spontaneous reaction.
2. which of the entities will react spontaneously with Zn(s) but not with Cd(s)
- Sn2+(aq)
- Mg2+(aq)
- H2O(l)
- Cr3+(aq)
3. find the strongest SOA AND SRA
a solution of iron(II) chloride is mixed with an acidifed sodium nitrate
b. solution of sodium hydroxide, potassium sulfite and chromium(II) nitrate are mixed.
4. which of the following is an entity that will copper(II) ions and also oxidize metallic nickel
5 years ago
Answered By Leonardo F
Question 1) First, let's review the standard electrode potentials for all the redox substances:
Zn2+ --> Zn -0.7628V
Cd2+ --> Cd -0.40V
Sn2+ --> Sn -0.13V
Mg2+ --> Mg -2.372V
H2O --> H2 -0.8277V
Cr3+ --> Cr -0.74V
Fe2+ --> Fe -0.44V
Co2+ --> Co -0.28V
Cu2+ --> Cu 0.337V
Au+ --> Au 1.83V
Ag+ --> Ag 0.7996V
H+ --> H2 0 V
Ni2+ --> Ni -0.25V
For test tube 1, since the reduction potential of iron is higher than zinc, iron will reduce to Fe(s) and zinc will oxidize to Zn2+. Hence, this is a spontaneous reaction.
For test tube 2, since the reduction potential of Sn is higher than Co, Sn2+ will reduce to Sn(s), while Co(s) will oxidize to Co2+. This is a spontaneous reaction.
For test tube 3, since there are both Cu2+ and Cu(s) in the tube, there is no difference in reduction potential between the metal and the solution. Hence, this is not a spontaneous reaction.
For test tube 4, since the reduction potential of Au is higher than Cu, Au(s) won't oxidize, and Cu2+ will not reduce. This is not a spontaneous reaction.
For test tube 5, since the reduction potential of Ag is higher than H, Ag(s) won't oxidize, and H+ will not reduce. This is not a spontaneous reaction.
For test tube 6, since the reduction potential of Ag is higher than Ni, Ag+ will oxidize to Ag(s), and Ni(s) will reduce to Ni2+. This is a spontaneous reaction.
Question 2) In this case, we will need to see if the chemical component has a reduction potential that is higher than zinc, but lower than cadmium. The only possible component is Cr3+(aq), because its reduction potential to Cr(s) is -0.74V. It is higher than the redcution potential of zinc (-0.7628V, so zinc will oxidize and cromium will reduce, spontaneously), but lower than the reduction potential of cadmium (-0.40V, so cadmium would reduce to Cd(s) and cromium would oxidize to Cr3+, but they are already as Cd(s) and Cr3+, so the reaction wouldn't happen).
Question 3) The potassium has an electrode potential of -2.92 V, going from K+ --> K(s), while the sodium has a vlue of -2.71V, going from Na+ --> Na(s). For the iron (Fe2+ --> Fe(s)), the value is -0.41 V. Finally, for chromium (Cr2+ --> Cr(s)), the electrode potential is -0.91 V. Whoever has the highest electrode potential has the highest potential to reduce. Hence, the metal that is going to reduce is iron and the iron (II) chloride will be the strongest oxidizing agent (SOA). Since the potassium has the lowest value of electrode potential, it's going to oxidize and the potassium sulfite will be the strongest reducing agent (SRA).
Question 4) We have to find which entity has an electrode potential that is lower than copper (II) but higher than metallic nickel. That way, it will suffer oxidation when copper ions are present and will suffer reduction when metallic nickel is present. The electrode potentials are:
Cu2+ --> Cu(s) +0.34 V
Ni2+ --> Ni(s) -0.26V
The only entity that has that property is Sn2+(aq), because it has an electrode potential of -0.14V, higher than copper (causing the reduction of copper(II) ions), but lower than nickel (causing the oxidation of metallic nickel).