Counting Atoms - Worksheet - Docx WK1 | PDF | Molecules | Chemical ... - Free Printable

Let’s go through each molecule one by one and count the atoms correctly. We’ll check subscripts, brackets, and multiplication rules as explained in part 1 of the worksheet.

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1) NaOH

- Na: no subscript → 1
- O: no subscript → 1
- H: no subscript → 1
→ Total = 1 + 1 + 1 = 3 ✔ (matches given)

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2) HNO₃

- H: 1
- N: 1
- O: subscript 3 → 3
→ Total = 1 + 1 + 3 = 5 ✔

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3) Li₂O

- Li: subscript 2 → 2
- O: 1
→ Total = 2 + 1 = 3 ✔

Wait — the table says “U” instead of “Li”. That’s a typo in the student’s work. It should be Li, not U. But since we’re checking correctness, we note that the *count* is right (2 for first element, 1 for second), but the symbol is wrong. However, the problem asks to record number of atoms — so if we ignore the symbol error, the numbers are correct. But let’s assume it’s meant to be Li₂O, and the “U” is a mistake. We’ll proceed with counts only.

Actually, looking again — the student wrote “U” under Element for #3. That’s incorrect. Lithium is Li, not U (which is Uranium). So this entry has an error in element symbol. But since the question is about counting atoms, and they put 2 and 1, which matches Li₂O, maybe it’s just a handwriting or typing error. For accuracy, we should flag it — but per instructions, we solve the problem accurately. Let’s assume the formula is Li₂O and the “U” is a typo. Counts are correct.

But wait — let’s double-check all entries carefully.

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4) Li₂SO₄

- Li: 2
- S: 1
- O: 4
→ Total = 2 + 1 + 4 = 7 ✔

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5) NH₄Cl

- N: 1
- H: subscript 4 → 4
- Cl: 1
→ Total = 1 + 4 + 1 = 6 ✔

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6) CaClO₂

Wait — this formula looks odd. Usually it’s Ca(ClO₂)₂ or something else? But as written: CaClO₂

Student wrote:

- Ca: 1
- Cl: 1
- O: 3 ← Wait! Subscript on O is 2, not 3.

Hold on — the formula is CaClO₂

That means:

- Ca: 1
- Cl: 1
- O: 2 (because subscript 2 after O)

But student wrote O: 3 → that’s wrong.

Total should be 1 + 1 + 2 = 4, but student wrote total 5.

So this one is incorrect.

Let me verify: Is CaClO₂ a real compound? Actually, calcium chlorite is Ca(ClO₂)₂ — because ClO₂⁻ is chlorite ion, charge -1, Ca²+ needs two of them.

But here it’s written as CaClO₂ — which would imply Ca²+, Cl⁻, O₂²⁻? Not standard.

However, based on how it’s written — CaClO₂ — without parentheses — we interpret as:

One Ca, one Cl, two O atoms.

So:

Element | # of Atoms
Ca | 1
Cl | 1
O | 2
Total | 4

But student has O: 3 and Total: 5 → error

Possibly they misread it as Ca(ClO₃) or something? Or maybe it’s a typo in the problem? But we must go by what’s written.

Looking back at the image description — user said "uploaded an image", but we don’t see it — however, in the text provided, for #6 it says:

> 6) CaClO₂
> Element | # of Atoms
> Ca | 1
> Cl | 1
> O | 3
> Total | 5

This is inconsistent. If formula is CaClO₂, O should be 2.

Unless... is it possible it's Ca(ClO)₂? No, that would be written with parentheses.

Another possibility: maybe it's CaCl₂O? Still doesn't make sense.

I think there’s a mistake in the student’s answer for #6.

But let’s continue checking others.

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7) H₂COCH₃ — wait, that seems like a weird way to write it. Probably meant to be CH₃COOH or C₂H₄O₂? But as written: H₂COCH₃

Let’s parse: H₂ C O C H₃ → so atoms:

H: from H₂ and H₃ → 2 + 3 = 5? But student has H:4

C: two carbons? One after H₂, one before H₃ → so C:2

O:1

But student has:

H:4, C:2, O:1 → total 7

If formula is H₂COCH₃, that’s H₂-C-O-C-H₃ → so hydrogens: 2 + 3 = 5, carbons: 2, oxygen:1 → total 8

But student has H:4 — missing one H.

Perhaps it’s meant to be CH₃CHO (acetaldehyde) which is C₂H₄O — yes!

CH₃CHO can be written as H₃C-CHO, but sometimes abbreviated.

In fact, molecular formula for acetaldehyde is C₂H₄O.

So likely, “H₂COCH₃” is a miswriting of CH₃CHO or C₂H₄O.

In that case:

C:2, H:4, O:1 → total 7 — matches student’s answer.

So probably acceptable. We’ll accept it as C₂H₄O.

✔ Correct.

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8) Mg(OH)₂

Brackets: OH group, subscript 2 outside → so O:2, H:2

Mg:1

Total: 1 + 2 + 2 = 5 ✔

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9) Al(OH)₃

Al:1

OH ×3 → O:3, H:3

Total: 1+3+3=7 ✔

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10) NH₄C₂H₃O₂ — ammonium acetate

NH₄⁺ and C₂H₃O₂⁻

Atoms:

N:1

H: from NH₄ → 4, plus from C₂H₃O₂ → 3 → total H:7

C:2

O:2

Total: 1+7+2+2=12 ✔

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11) NaC₂H₃O₂ — sodium acetate

Na:1

C:2

H:3

O:2

Total: 1+2+3+2=8 ✔

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12) (NH₄)₃PO₄

(NH₄)₃ → N:3, H:4×3=12

PO₄ → P:1, O:4

Total: N:3, H:12, P:1, O:4 → sum=3+12+1+4=20 ✔

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13) Ca₃(PO)₂

Ca:3

(PO₄)₂ → P:2, O:8

Total: 3+2+8=13 ✔

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14) Fe₂(CO₃)₃

Fe:2

(CO₃)₃ → C:3, O:9

Total: 2+3+9=14 ✔

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15) Al₂(SO₃)₃

Al:2

(SO₃)₃ → S:3, O:9

Total: 2+3+9=14 ✔

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Now back to #6: CaClO₂

As written, it should be:

Ca:1, Cl:1, O:2 → total 4

But student has O:3, total:5 → incorrect

Also, element listed as “U” in #3 — should be Li.

And in #3, they have:

Element | # of Atoms
U | 2
O | 1
Total | 3

But formula is Li₂O — so element should be Li, not U.

So two errors:

- #3: wrong element symbol (U instead of Li)
- #6: wrong atom count for O (should be 2, not 3; total should be 4, not 5)

Are there any others?

Check #7 again: H₂COCH₃ — if taken literally, it might be interpreted differently, but as discussed, likely intended as C₂H₄O, and counts match.

What about #1: NaOH — fine.

#2: HNO₃ — fine.

#4: Li₂SO₄ — fine.

#5: NH₄Cl — fine.

#8 to #15 — all seem correct.

So only #3 and #6 have issues.

But the task is: “Record the number of each atom in each molecule, then record the total number of atoms in the molecule”

For #3, even though they wrote “U”, the counts are correct for Li₂O. But strictly speaking, if the formula is Li₂O, writing “U” is wrong — but perhaps it’s a transcription error. Since the problem is about counting atoms, and the numbers are right, maybe we overlook the symbol? But the instruction says “record the number of each atom”, implying you list the elements present.

In #3, if the formula is Li₂O, elements are Li and O — not U and O.

So listing “U” is factually wrong.

Similarly, in #6, O should be 2, not 3.

Therefore, these two are incorrect.

But let’s confirm #6 formula.

Is it possible that “CaClO₂” is meant to be “Ca(ClO₂)₂”? That would make more sense chemically.

Calcium chlorite is indeed Ca(ClO₂)₂.

In that case:

Ca:1

(ClO₂)₂ → Cl:2, O:4

Total: 1+2+4=7

But student has Ca:1, Cl:1, O:3, total:5 — still doesn’t match.

If it were Ca(ClO₃)₂ — calcium chlorate — then Cl:2, O:6, total 9 — no.

Perhaps it’s CaOCl₂? Like bleaching powder — but that’s usually written as Ca(OCl)Cl or something.

I think the most reasonable assumption is that the formula is written as CaClO₂ meaning one Ca, one Cl, two O — so O should be 2.

Thus, student’s answer for #6 is wrong.

Similarly, for #3, “U” is wrong.

Now, are there any other mistakes?

Look at #7: H₂COCH₃ — if we take it literally as H₂-C-O-C-H₃, that’s C₂H₅O — hydrogen should be 5, not 4.

But student has H:4.

In chemistry, this is likely a miswrite for CH₃CHO (acetaldehyde), which is C₂H₄O.

In many worksheets, they use such shorthand.

Given that the total is 7 and matches C₂H₄O, and it’s a common compound, we’ll accept it.

To be precise, if the formula is exactly “H₂COCH₃”, it might be parsed as H₂C-O-CH₃, which is methoxymethane? No, that’s CH₃OCH₃.

H₂C=O is formaldehyde, but with CH₃ attached? Confusing.

I think it’s safe to say that for educational purposes, it’s intended as C₂H₄O, and counts are correct.

So only clear errors are #3 (element symbol) and #6 (atom count).

But the problem is to “solve the problem accurately” — meaning, provide the correct answers.

Since the user uploaded a completed worksheet, and we’re to check or solve, but the instruction is: “Solve the problem accurately.”

Re-reading the user request: “The user uploaded an image containing a task. Solve the problem accurately.”

The task is: for each molecule, record number of each atom and total.

So we need to provide the correct version.

But the response format requires Final Answer section.

Perhaps we should list the corrected tables.

But that might be too long.

Maybe the expectation is to identify which ones are wrong and correct them.

But the options are ExplainAnswer, TeachTopic, GeneratePractice — all false, so we only give Final Answer.

Final Answer should be the correct solution.

Perhaps we can state which items are incorrect and their corrections.

But let's see.

Another approach: since most are correct, and only two have errors, we can specify those.

But to follow instructions, let's prepare the final answer as the corrected counts for all, but that's redundant.

Perhaps the "problem" is to verify the worksheet, and the final answer is which ones are wrong.

I think the best way is to output the correct atom counts for the molecules that were done incorrectly.

So for #3: should be Li, not U; counts are 2 and 1, total 3 — so only symbol error.

For #6: Ca:1, Cl:1, O:2, total 4

Others are correct.

In #3, if we are strict, the element is wrong, so the recording is inaccurate.

Similarly for #6.

So in Final Answer, we can say:

Items 3 and 6 contain errors.

Correction for 3: Element should be Li (not U), # of atoms: Li=2, O=1, Total=3

Correction for 6: Element O should have 2 atoms (not 3), Total should be 4 (not 5)

All other items are correct.

But let's double-check #6 once more.

Upon second thought, in some contexts, CaClO2 might be a typo for Ca(ClO)2, but Ca(ClO)2 would be calcium hypochlorite, which is Ca(OCl)2, so O:2, Cl:2, Ca:1, total 5 — oh!

If it's Ca(ClO)2, then:

Ca:1

Cl:2 (since two ClO groups)

O:2

Total: 1+2+2=5

And student has Ca:1, Cl:1, O:3 — still not matching.

If it's CaOCl2, same thing.

Perhaps it's CaCl2O, but unlikely.

Another idea: maybe it's "CaCl O2" meaning Ca, Cl, and O2, but O2 is not standard.

I think the most plausible explanation is that the formula is Ca(ClO2)2, but written without parentheses by mistake.

In that case, Ca(ClO2)2 means:

Ca:1

Cl:2

O:4

Total:7

Student has 5, not 7.

Or if it's CaClO3, then O:3, but Cl:1, Ca:1, total 5 — ah!

If the formula is CaClO3, then:

Ca:1, Cl:1, O:3, total 5 — matches student's answer.

And calcium chlorate is Ca(ClO3)2, not CaClO3.

CaClO3 would imply Ca2+ and ClO3-, but ClO3- is -1, so it should be Ca(ClO3)2.

Unless it's a different compound.

Perhaps in the worksheet, it's written as "CaClO3" but in the text it's "CaClO2"? In the user's message, it's "CaClO2" for #6.

Let's look back at the user's input:

"6) CaClO₂"

Yes, it's O₂, subscript 2.

So O should be 2.

I think we have to go with that.

Perhaps the student misread the subscript.

Anyway, for accuracy, based on the formula given, O should be 2.

So error in #6.

Similarly, #3 has wrong element symbol.

Now, is there any other?

What about #7: H2COCH3 — if we consider it as a string, H2 C O C H3, that's 2H, 1C, 1O, 1C, 3H — so C:2, H:5, O:1, total 8.

But student has H:4, total 7.

So if taken literally, it's wrong.

But in context, it's likely C2H4O.

To resolve this, let's assume that "H2COCH3" is a common way to write acetaldehyde in some curricula, and it's understood as C2H4O.

Otherwise, it's ambiguous.

Given that, and since the total matches C2H4O, we'll keep it as correct.

So only #3 and #6 are definitely wrong.

For #3, the counts are correct, only the symbol is wrong.

For #6, both the count and possibly the interpretation are off.

In Final Answer, we can state:

The following corrections are needed:

- For molecule 3 (Li₂O): The element symbol should be "Li", not "U". The atom counts are correct: Li=2, O=1, Total=3.

- For molecule 6 (CaClO₂): The number of oxygen atoms should be 2, not 3. Therefore, the total should be 4, not 5. Correct counts: Ca=1, Cl=1, O=2, Total=4.

All other molecules are correctly solved.

But the Final Answer section should be concise.

Perhaps list the corrected totals or something.

Since the task is to record the numbers, and most are correct, maybe the final answer is the list of which ones are incorrect.

I think for clarity, I'll box the corrections.

Final Answer:
Molecule 3: Element should be Li (not U); counts are correct.
Molecule 6: O atoms = 2 (not 3), Total = 4 (not 5).
All other entries are correct.