The Nature Of Science And Engineering, Physical Science Worksheet With Answers - Minnesota K-12 Page 8
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1223. Do you notice a trend or pattern for the changes in oxidation numbers from
the previous problem?
The oxidation numbers decrease. This term is known as reduction.
24. Let’s called this trend reduction. Use the following equation as another
example to consider this term. What happens to chlorine in reaction four? Is
there a general trend that can be stated for any species that is reduced?
IV. 2Fe + 3Cl
→ 2FeCl
2
3
Oxidation number goes from 0 to 1- (Number is still decreasing-becoming more
negative; just as before.)
25. Look at all four reactions at once. (They are reprinted below for your
convenience). Count the number of valence electrons in each of the metal atoms
and ions before and after the reactions. You will need to make a table to organize
your results.
I. 4Fe + 3O
→ 2Fe
O
2
2
3
II. 2Cu + O
→ 2CuO
2
III. 2Mg + O
→ 2MgO
2
IV. 2Fe + 3Cl
→ 2FeCl
2
3
Reaction
Metal Electrons Before
Metal Electrons After
-
-
I
4x8=32e
4(8-3)=20e
-
-
II
2x11=22e
2(11-1)=20e
-
-
III
2x2=4e
2x0=0e
-
-
IV
2x8=16e
2x6=12e
26. Generally speaking, what happens to the metals in these reactions?
The metals are losing electrons in these reactions.
27. When looking at electrons, what can be said about the term, oxidation?
When a species is oxidized, it loses electrons.
28. Count the number of electrons in each of the oxygens (and the chloride)
before and after the reactions. You will need to make a table to organize your
results.
Reaction
O or Cl Electrons Before
O or Cl Electrons After
-
-
I
6x6=36e
6(6+2)=48e
-
-
II
2x6=12e
2(6+2)=16e
-
-
III
2x612e
2(6+2)=16e
-
-
IV
6x7=42e
6(7+1)=48e
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