Which of the following statements are true?

Question

Which of the following statements are true?


For statements a) through d) use the reaction:


SiCl4(l) + 2Mg(s) --> 2MgCl2(s) + Si(s)



a) Mg is the reducing agent

b) SiCl4 is the reducing agent

c) Mg is reduced

d) SiCl4 (or Si in SiCl4) is reduced

e) CH4(g) + 2O2(g) --> CO2(g) + 2H2O(g) is a redox reaction

f) Al(OH)4-(aq) --> AlO2-(aq) + 2H2O(l) is a redox reaction

Note: you can have more than one answer.

Answer 1

Find the oxidation states of each of the molecules on each side of the equation. If the number increases it is oxidized (loss of electrons is oxidation). A reducing agent is oxidized during the process. Its your homework, you do the math.

Answer 2

1. Look for 2 charge changes: the Si goes from +4 (in the SiCl4) to 0 in the solid

The Mg goes from 0 (as the solid) to +2 in the MgCl2.

2. Figure out which one LOST electrons (oxidation) and which one GAINED electrons (reduction).

mneumonic device: LEO says GER
(loss of electrons = oxidation; gain electrons = reduction)

3. The element that undergoes oxidation CAUSES reduction and is called the reducing agent. The element that undergoes reduction CAUSES oxidation and is called the oxidizing agent.

In e) and f) there are no charge changes so the reactions are not redox reactions

Answer 3

a) true
b) false
c) true
d) false
e) true
f) true