Hi, I need some assistance understanding how to approach the following questions,
a) Oxidation numbers for each.
b) Which atom is being reduced and why.
c) Which atom is being oxidized and why.
d) Which molecule/ion is the reducing agent and why.
e) Which molecule/ion is the oxidizing agent and why.
To assign oxidation numbers you need to know a few rules about the system.
- Hydrogen is always plus 1 (except when bonded to a group 1 or 2 metal)
- Oxygen is always -2, (except when bonded to fluorine)
- Most halides are always -1
- Group 1 metals are always +1
- Group 2 metals are always +2
This solution is comprised of a detailed explanation of how to approach this chemistry based problem. Tips for solving these types of questions, particularly in terms of assigning oxidation numbers, are provided and will be useful in understanding how to complete future questions of this nature.
Oxidation and Reduction
1. Define the following concepts:
a) oxidizing agent
b) oxidized substance
c) reducing agent
d) reduced substance
2. Determine the oxidation numbers of the underlined elements in the following formulas:
3. Balance the following equations by the half-cell method. Show both half-cell reactions and identify them as oxidation or reduction.
a) SO32- + MnO4- + H+ ←→ Mn2+ + SO42- + H2O(l)
b) Cl2(g) + OH- ←→ Cl- + ClO3- + H2O(l)
c) SO42- + I- + H+ ←→ S2- + I2(s) + H2O(l)
i) A reacts spontaneously with 1 mol/L BNO3, 1 mol/L D(NO3)2 and dilute sulfuric acid. A does not react with 1 mol/L C(NO3)2.
ii) B does not react spontaneously with any of the 1 mol/L solutions above or with dilute sulfuric acid.
iii) C reacts spontaneously with dilute sulfuric acid and with 1 mol/L solutions of all the other metallic salts.
iv) D reacts spontaneously with 1 mol/L BNO3. It does not react with dilute sulfuric acid.
a) Use the observations and arrange the following five reduction half-cell reactions in order, the one with the largest positive reduction potential listed first.
A2+ + 2e- → A(s)
B+ + e- → B(s)
C2+ + 2e- → C(s)
D2+ + 2e- → D(s)
2H+ + 2e- → H2(g)
b) Which metal is the best reducing agent?
c) Which ion is the best oxidizing agent?
5. Calculate the voltage of a standard cell with the following half-cell reactions:
Ni(s) → Ni2+ + 2e-
2e- + Cl2(g) → 2Cl-
6. a) What metal might you fasten to the hull of an aluminum boat to give it cathodic protection in sea water?
b) Name two metals you would not use. Explain the choices.
7. By the electrolysis of water, 11.2 L of oxygen at STP was prepared.
a) What charge was required?
b) If a current of 0.5 A was used, how long did it take?
8. Aluminum is one of the most widely used metals. Aluminum is made by electrolyzing aluminum oxide in a solvent called cryolite.
a)Identify the products of the anode and cathode half-reactions that occur during the electrolysis of aluminum oxide.
b) Why is it important to recycle as much aluminum as possible?
c) Identify one environmental concern and one health concern associated with the product of aluminum.