Monday 11 June 2012

Electrolytes and Non-electrolytes Quiz


1. KCl is placed inside a container filled with 1 L of water.
   a. For ever 1 mol of the substance, how is the proportion of the number of particles in the container?
   b. Determine the degree of dissociation (α) of the substance!
   c. Is the solution considered a strong, weak, or non-electrolyte?

2. a. Based on the gain or the loss of oxygen, where do oxidation and reduction take place in the following reaction?
      Zn   +   PbO   ->   ZnO   +   Pb
   b. The oxidizing agent is ...
   c. The reducing agent is ...

3. a. Based on the gain or the loss of hydrogen, where do oxidation and reduction take place in the following reaction?
      H2S   +   Br2   ->   2 HBr   +    S
   b. The oxidizing agent is ...
   c. The reducing agent is ...

4. a. Based on the gain or the loss of electrons, where do oxidation and reduction take place in the following redox reactions?
      Cl2(aq)   +   2 Br-(aq)   ->   2 Cl-(aq)   +   Br2(aq)
   b. Write the ionic half equation of the oxidation!
   c. Write the ionic half equation of the reduction!

5. Write down the oxidation states of the elements in the following compounts!
   a. H3PO4
   b. ClF3
   c. MgH2
   d. CaO2
   e. NaIO3

6. a. Based on the changes in oxidation state, where do oxidation and reduction take place in the following reactions:
      2 KClO3(aq)   +   3 S(s)   ->   2 KCl(aq)   +   3 SO2(g)
   b. The oxidizing agent is ...
   c. The reducing agent it ...
   d. The oxidation result is ...
   e. The reduction result is ....


Solutions:
1. c. α = 1 so it's a strong electrolyte

2. oxidation is from Zn to ZnO, reduction is from PbO to Pb.
   oxidizing agent: PbO
   reducing agent: Zn
   tip: the one where oxidation starts from is the reducing agent

3. oxidation is from H2S to S, reduction is from Br2 2 HBr.
   oxidizing agent: Br2
   reudcing agent: H2S

4. oxidation is from 2 Br- to Br2, reduction is from Cl2 to 2 Cl-
   ionic half equation for oxidation:  2 Br- -> Br+ 2e-
   ionic half equation for reduction: Cl+ 2e-> 2 Cl-

5. a. +1 +5 -2
   b. +3 -1
   c. +2 -1
   d. +2 -1
   e. +1 +5 -2

6. oxidation is from 3 S to 3 SO2, reduction is from 2 KClO3 to 2 KCl
   oxidizing agent: KClO3
   reducting agent: S
   oxidation result: SO2
   reduction result: KCl

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