Solved CHE 108 Oxidation Number Worksheet Prof. Dcora | Chegg.com - Free Printable

Let’s go step by step through each compound and assign oxidation numbers using the rules given.

We’ll use these key rules (in order of priority):

1. Pure element → oxidation number = 0
2. Monatomic ion → equals its charge
3. Fluorine always -1 in compounds
4. Group 1 = +1, Group 2 = +2, Al = +3
5. Hydrogen = +1 (unless with metal → then -1)
6. Oxygen = -2 (usually)
7. Sum of all atoms in neutral compound = 0; in polyatomic ion = charge of ion

---

1. Cl₂
→ Pure element → Cl = 0

2. Cr⁻
→ Monatomic ion → Cr = -1 (charge is -1)

3. Na
→ Pure element → Na = 0

4. Na⁺
→ Monatomic ion → Na = +1

5. O₂
→ Pure element → O = 0

6. N₂
→ Pure element → N = 0

7. Al³⁺
→ Monatomic ion → Al = +3

8. H₂O
→ Neutral compound.
Oxygen = -2 (rule 6)
Hydrogen = +1 (rule 5 — not combined with metal)
Check: 2*(+1) + (-2) = 0 → correct
So: H = +1, O = -2

9. NO₂ *(Note: This is likely nitrogen dioxide, a neutral molecule)*
→ Neutral compound.
Oxygen = -2 each → 2*(-2) = -4
Let N = x
x + (-4) = 0 → x = +4
So: N = +4, O = -2

*(Wait — but sometimes NO₂ can be confused with nitrite ion NO₂⁻. But here it's written as “NO₂” without charge, so we assume neutral molecule. However, let’s double-check context. In many worksheets, if it’s an ion, they write the charge. Since no charge is shown, we treat as neutral. BUT — actually, common practice: NO₂ as a formula alone often refers to the radical nitrogen dioxide, which is neutral. So yes, N = +4.)*

But wait — let me check rule precedence again. Rule 6 says oxygen is -2 unless... no exception here. So yes.

Actually, hold on — in some curricula, they might expect you to know that NO₂ is a neutral molecule with N=+4. Let’s stick with that.

10. KCl
→ Neutral compound.
K is Group 1 → +1
Cl must balance → -1
Check: +1 + (-1) = 0 → good
So: K = +1, Cl = -1

11. NH₃
→ Neutral compound.
H = +1 (not with metal) → 3*(+1) = +3
N + 3 = 0 → N = -3
So: N = -3, H = +1

12. CaH₂
→ Calcium hydride.
Ca is Group 2 → +2
H is combined with metal → so H = -1 (rule 5 exception!)
Check: +2 + 2*(-1) = 0 → correct
So: Ca = +2, H = -1

13. Na₂O₂
→ Sodium peroxide.
Na is Group 1 → +1 each → 2*(+1) = +2
This is a peroxide! Important: In peroxides, oxygen is -1, not -2.
Rule 6 says oxygen is -2 *unless*... well, peroxides are an exception. Even though not listed explicitly, standard knowledge: O in peroxides = -1.
Check: 2*(+1) + 2*(-1) = 0 → correct
So: Na = +1, O = -1

*(Note: If student doesn’t know peroxide rule, they might get wrong answer. But since this is CHE 108, likely covered. We’ll go with standard chemistry knowledge.)*

14. SiO₂
→ Silicon dioxide. Neutral.
O = -2 each → 2*(-2) = -4
Si + (-4) = 0 → Si = +4
So: Si = +4, O = -2

15. CaCl₂
→ Neutral compound.
Ca is Group 2 → +2
Cl must be -1 each → 2*(-1) = -2
Check: +2 + (-2) = 0 → good
So: Ca = +2, Cl = -1

---

Now let’s fill the table:

| # | Formula | Element | Oxidation Number | Element | Oxidation Number |
|---|---------|---------|------------------|---------|------------------|
| 1 | Cl₂ | Cl | 0 | | |
| 2 | Cr⁻ | Cr | -1 | | |
| 3 | Na | Na | 0 | | |
| 4 | Na⁺ | Na | +1 | | |
| 5 | O₂ | O | 0 | | |
| 6 | N₂ | N | 0 | | |
| 7 | Al³⁺ | Al | +3 | | |
| 8 | H₂O | H | +1 | O | -2 |
| 9 | NO₂ | N | +4 | O | -2 |
|10 | KCl | K | +1 | Cl | -1 |
|11 | NH₃ | N | -3 | H | +1 |
|12 | CaH₂ | Ca | +2 | H | -1 |
|13 | Na₂O₂ | Na | +1 | O | -1 |
|14 | SiO₂ | Si | +4 | O | -2 |
|15 | CaCl₂ | Ca | +2 | Cl | -1 |

Wait — I think I misnumbered. The original table has 18 rows? Let me recount from image description.

Looking back at user input:

The table lists:

1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
... and then stops? Wait, user wrote up to 18? Let me check:

In the text provided:

"1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16. ?
17. ?
18. ?"

Wait — in the initial problem statement, after 15 it says:

"16. Na₂O₂" — no, wait, let me re-read the user’s text:

Actually, looking carefully:

User wrote:

```
1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16. ?
17. ?
18. ?
```

Wait — no, in the actual text block, it goes:

After "15. CaCl₂", there is nothing else? But the table shows 18 rows? Let me count the lines in the user’s message:

From:

"1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16.
17.
18. "

Actually, in the original problem, row 16 is blank? Or did I miss?

Wait — looking back at the very first part:

The user pasted:

```
1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16.
17.
18.
```

But in the table structure, it has columns for two elements. For single-element species, only one column is filled.

Also, I notice: in row 9, it's "NO₂" — but in my calculation above, I assumed neutral. However, in many introductory courses, when they write "NO₂" without charge, they might mean the nitrite ion? No — nitrite is NO₂⁻. Nitrogen dioxide is NO₂ (neutral).

But let’s confirm with sum: if it were NO₂, then N + 2*(-2) = -1 → N = +3. But since no charge is indicated, we should treat as neutral → N=+4.

However, I recall that in some textbooks, they list NO₂ as having N=+4 for the molecule.

But wait — let’s check row 13: Na₂O₂ — that’s sodium peroxide, where O is -1.

Similarly, for consistency, we must apply exceptions.

Another thing: row 2 is Cr⁻ — that’s unusual, but we take it as monatomic ion with charge -1.

Now, what about rows 16-18? They are empty in the user’s input? Or did I miscount?

Looking again at the user’s message:

They wrote:

```
1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16.
17.
18.
```

And in the table, it has 18 rows. But rows 16-18 have no formulas? That can’t be right.

Wait — perhaps I missed something. Let me read the original text more carefully.

In the user’s input, after "15. CaCl₂", it continues:

"16. Na₂O₂" — no, wait, no — let's copy exactly:

From the beginning:

"1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16.
17.
18. "

Actually, in the table layout, it's possible that rows 16-18 are meant to be filled, but no formulas are given? That doesn't make sense.

Perhaps there's a typo in the user's paste. Looking back at the initial problem statement, I see:

In the table, after 15. CaCl₂, it might continue, but in the text, it cuts off.

Wait — let's look at the very end of the user's message:

"18. CaCl₂" — no, row 15 is CaCl₂, and then 16,17,18 are blank? That can't be.

I think I found the issue. In the user's input, the list goes up to 18, but in the text, after 15, it says:

"16. Na₂O₂" — no, let's count the lines in the code block:

Actually, in the markdown, it's:

```
1. Cl₂
2. Cr⁻
3. Na
4. Na
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16.
17.
18.
```

But that would mean rows 16-18 are empty, which is unlikely.

Perhaps "16." is missing the formula? Or maybe it's a continuation.

Another possibility: in the original worksheet, row 16 might be something like "SO₄²⁻" or similar, but it's not provided.

Given that, and since the user only provided up to 15 with formulas, and 16-18 are blank, I will assume that only rows 1-15 are to be filled, and 16-18 are either errors or not required.

But to be safe, let's check if there's any mention later.

In the user's message, after the table, there is no additional information.

Perhaps "16." is meant to be "CO₂" or something, but it's not specified.

Given the constraints, I will provide answers for rows 1-15 as per the formulas given, and for 16-18, since no formulas are provided, I'll leave them blank or note that.

But that seems odd.

Let me double-check the user's input string:

"1. Cl₂
2. Cr⁻
3. Na
4. Na⁺
5. O₂
6. N₂
7. Al³⁺
8. H₂O
9. NO₂
10. KCl
11. NH₃
12. CaH₂
13. Na₂O₂
14. SiO₂
15. CaCl₂
16.
17.
18. "

Yes, rows 16-18 have no formulas. Perhaps it's a formatting error, and the worksheet has only 15 items, but the table has 18 rows for space.

To resolve this, I will complete rows 1-15 as calculated, and for 16-18, since no compounds are given, I cannot assign oxidation numbers. But that might not be satisfactory.

Another idea: perhaps "16." is "MgO" or something common, but it's not specified.

Given the instructions, I should only solve what is given. So I'll provide the table for 1-15, and omit 16-18 or mark as N/A.

But let's see the example: the example was FeO, which is not in the list.

Perhaps in the original worksheet, rows 16-18 are present, but in the user's paste, they are missing.

To be thorough, I recall that in some versions of this worksheet, row 16 is "CO₂", 17 is "SO₄²", 18 is "PO₄³⁻", but since not provided, I won't guess.

For now, I'll proceed with 1-15.

But wait — in the user's message, after "15. CaCl₂", it says "16." and then nothing, but in the table, it has columns, so perhaps it's intentional to have only 15.

Let's count the number of items listed: from 1 to 15, that's 15 items. Rows 16-18 might be extra space.

I think it's safe to provide answers for 1-15.

So final table:

Row 1: Cl₂ → Cl: 0
Row 2: Cr⁻ → Cr: -1
Row 3: Na → Na: 0
Row 4: Na⁺ → Na: +1
Row 5: O₂ → O: 0
Row 6: N₂ → N: 0
Row 7: Al³⁺ → Al: +3
Row 8: H₂O → H: +1, O: -2
Row 9: NO₂ → N: +4, O: -2 [assuming neutral molecule]
Row 10: KCl → K: +1, Cl: -1
Row 11: NH₃ → N: -3, H: +1
Row 12: CaH₂ → Ca: +2, H: -1
Row 13: Na₂O₂ → Na: +1, O: -1 [peroxide]
Row 14: SiO₂ → Si: +4, O: -2
Row 15: CaCl₂ → Ca: +2, Cl: -1

For rows 16-18, since no formulas are provided, I will not include them in the final answer, or state that they are incomplete.

But to match the table format, perhaps the user expects only the given ones.

Another thought: in the initial problem, the table has 18 rows, but only 15 are filled with formulas in the text. Perhaps "16." is "Fe₂O₃" or something, but it's not specified.

Given the instructions to solve accurately, and since no formulas for 16-18 are given, I will provide the answer for 1-15 only.

So, compiling the final answer as a table.

Final Answer:

| # | Formula | Element | Oxidation Number | Element | Oxidation Number |
|---|---------|---------|------------------|---------|------------------|
| 1 | Cl₂ | Cl | 0 | | |
| 2 | Cr⁻ | Cr | -1 | | |
| 3 | Na | Na | 0 | | |
| 4 | Na | Na | +1 | | |
| 5 | O₂ | O | 0 | | |
| 6 | N₂ | N | 0 | | |
| 7 | Al³⁺ | Al | +3 | | |
| 8 | H₂O | H | +1 | O | -2 |
| 9 | NO₂ | N | +4 | O | -2 |
|10 | KCl | K | +1 | Cl | -1 |
|11 | NH₃ | N | -3 | H | +1 |
|12 | CaH₂ | Ca | +2 | H | -1 |
|13 | Na₂O₂ | Na | +1 | O | -1 |
|14 | SiO₂ | Si | +4 | O | -2 |
|15 | CaCl₂ | Ca | +2 | Cl | -1 |
|16 | | | | | |
|17 | | | | | |
|18 | | | | | |

Since rows 16-18 have no formulas, they are left blank.

But to be precise, I'll output only the filled rows or as per requirement.

Given that the user might expect all 18, but only 15 are defined, I think it's best to provide what is solvable.

Perhaps "16." is a typo and should be "CO₂", but I won't assume.

I recall that in some sources, this worksheet has:

16. CO₂
17. SO₄²⁻
18. PO₄³⁻

But since not provided, I'll stick to given data.

For the sake of completeness, if I must fill 16-18, I can't.

Another idea: in the user's message, after "15. CaCl₂", it says "16." and then in the next line "17." etc., but no text, so likely empty.

I think the intended answer is for 1-15.

So I'll box the table for 1-15.

But the response format requires "Final Answer" section with only the final correct answer.

So I'll write the table as text.

Final Answer:

1. Cl₂: Cl = 0
2. Cr⁻: Cr = -1
3. Na: Na = 0
4. Na⁺: Na = +1
5. O₂: O = 0
6. N₂: N = 0
7. Al³: Al = +3
8. H₂O: H = +1, O = -2
9. NO₂: N = +4, O = -2
10. KCl: K = +1, Cl = -1
11. NH₃: N = -3, H = +1
12. CaH₂: Ca = +2, H = -1
13. Na₂O₂: Na = +1, O = -1
14. SiO₂: Si = +4, O = -2
15. CaCl₂: Ca = +2, Cl = -1

Rows 16-18: No formulas provided, so not applicable.

But to match the table format, perhaps list as above.

Since the instruction is to provide the final answer, and it's a table, I'll format it cleanly.

Final Answer:
\boxed{
\begin{array}{|c|c|c|c|c|c|}
\hline
\text{\#} & \text{Formula} & \text{Element} & \text{Oxidation number} & \text{Element} & \text{Oxidation number} \\
\hline
1 & \text{Cl}_2 & \text{Cl} & 0 & & \\
\hline
2 & \text{Cr}^- & \text{Cr} & -1 & & \\
\hline
3 & \text{Na} & \text{Na} & 0 & & \\
\hline
4 & \text{Na}^+ & \text{Na} & +1 & & \\
\hline
5 & \text{O}_2 & \text{O} & 0 & & \\
\hline
6 & \text{N}_2 & \text{N} & 0 & & \\
\hline
7 & \text{Al}^{3+} & \text{Al} & +3 & & \\
\hline
8 & \text{H}_2\text{O} & \text{H} & +1 & \text{O} & -2 \\
\hline
9 & \text{NO}_2 & \text{N} & +4 & \text{O} & -2 \\
\hline
10 & \text{KCl} & \text{K} & +1 & \text{Cl} & -1 \\
\hline
11 & \text{NH}_3 & \text{N} & -3 & \text{H} & +1 \\
\hline
12 & \text{CaH}_2 & \text{Ca} & +2 & \text{H} & -1 \\
\hline
13 & \text{Na}_2\text{O}_2 & \text{Na} & +1 & \text{O} & -1 \\
\hline
14 & \text{SiO}_2 & \text{Si} & +4 & \text{O} & -2 \\
\hline
15 & \text{CaCl}_2 & \text{Ca} & +2 & \text{Cl} & -1 \\
\hline
16 & & & & & \\
\hline
17 & & & & & \\
\hline
18 & & & & & \\
\hline
\end{array}
}

Note: Rows 16-18 have no formulas specified, so they are left blank. If additional compounds were intended, please provide them for completion.