Chemistry Formula Mass Worksheet - —F ——————— ——— JRAM FORMULA ... - Free Printable

Let’s go step by step to calculate the molar mass (also called formula mass) for each compound listed. Molar mass is the sum of the atomic masses of all atoms in one mole of a substance, measured in grams per mole (g/mol).

We’ll use standard atomic masses from the periodic table (rounded to two decimal places unless otherwise noted):

- H = 1.01
- O = 16.00
- C = 12.01
- N = 14.01
- S = 32.07
- Cl = 35.45
- Na = 22.99
- K = 39.10
- Ca = 40.08
- Fe = 55.85
- Al = 26.98
- P = 30.97
- Mg = 24.31
- Cu = 63.55
- Zn = 65.38
- Ag = 107.87
- Ba = 137.33
- Pb = 207.20

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Now let’s compute each:

1. H₂O

= 2×H + 1×O = 2(1.01) + 16.00 = 2.02 + 16.00 = 18.02 g/mol

✔ Matches student answer.

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2. CO₂

= 1×C + 2×O = 12.01 + 2(16.00) = 12.01 + 32.00 = 44.01 g/mol

Student wrote “44” — acceptable if rounded, but we’ll keep precise.

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3. NO₃⁻ (nitrate ion — treat as neutral for molar mass calculation)

Actually, this should be written as part of a compound, but since it's listed alone, we assume they mean the nitrate *ion*’s mass:
= 1×N + 3×O = 14.01 + 3(16.00) = 14.01 + 48.00 = 62.01 g/mol

But wait — looking at the image, #3 says “NO₃” and student wrote “62.01”. That matches.

However, note: sometimes students confuse NO₃ with NO₂ or others. But here it’s correct.

Wait — actually, looking again at the original list:

The user’s image shows:

1. H₂O → 18.02 ✔
2. CO₂ → 44.01? Student wrote “44” — okay
3. NO₃ → 62.01 ✔
4. CaCO₃ → ?
5. Al₂(SO₄)₃ → ?
6. (NH₄)₂SO₄ → ?
7. Cu(NO₃)₂ → ?
8. Mg(OH)₂ → ?
9. FeCl₃ → ?
10. K₂Cr₂O₇ → ?
11. AgNO₃ → ?
12. BaSO₄ → ?
13. Pb(NO₃)₂ → ?
14. Na₂CO₃ → ?

Wait — I think I misread the numbering. Let me re-list based on what’s visible in the image description.

Actually, from the OCR-like text provided:

It says:

1. H₂O → 18.02
2. CO₂ → 44
3. NO₃ → 62.01
4. CaCO₃ → 100.09
5. Al₂(SO₄)₃ → 342.17
6. (NH₄)₂SO₄ → 132.17
7. Cu(NO₃)₂ → 187.57
8. Mg(OH)₂ → 58.33
9. FeCl₃ → 162.20
10. K₂Cr₂O₇ → 294.19
11. AgNO₃ → 169.88
12. BaSO₄ → 233.40
13. Pb(NO₃)₂ → 331.21
14. Na₂CO₃ → 105.99

Wait — but the student has handwritten answers next to them. Some are correct, some may have errors.

Our job is to solve accurately, not just verify.

So let’s recalculate each carefully.

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## Step-by-step Calculations:

1. H₂O

2×1.01 + 16.00 = 2.02 + 16.00 = 18.02 g/mol

2. CO₂

12.01 + 2×16.00 = 12.01 + 32.00 = 44.01 g/mol

3. NO₃ (as ion — still calculate atomic mass sum)

14.01 + 3×16.00 = 14.01 + 48.00 = 62.01 g/mol

*(Note: In reality, ions don’t have “molar mass” independently without counterions, but for homework purposes, we calculate the formula unit mass.)*

4. CaCO₃

Ca: 40.08
C: 12.01
O₃: 3×16.00 = 48.00
Total = 40.08 + 12.01 + 48.00 = 100.09 g/mol

5. Al₂(SO₄)₃

Al₂: 2×26.98 = 53.96
S₃: 3×32.07 = 96.21
O₁₂: 12×16.00 = 192.00
Total = 53.96 + 96.21 + 192.00 = 342.17 g/mol

6. (NH₄)₂SO₄

N₂: 2×14.01 = 28.02
H₈: 8×1.01 = 8.08
S: 32.07
O₄: 4×16.00 = 64.00
Total = 28.02 + 8.08 + 32.07 + 64.00 = 132.17 g/mol

7. Cu(NO₃)₂

Cu: 63.55
N₂: 2×14.01 = 28.02
O₆: 6×16.00 = 96.00
Total = 63.55 + 28.02 + 96.00 = 187.57 g/mol

8. Mg(OH)₂

Mg: 24.31
O₂: 2×16.00 = 32.00
H₂: 2×1.01 = 2.02
Total = 24.31 + 32.00 + 2.02 = 58.33 g/mol

9. FeCl₃

Fe: 55.85
Cl₃: 3×35.45 = 106.35
Total = 55.85 + 106.35 = 162.20 g/mol

10. K₂Cr₂O₇

K₂: 2×39.10 = 78.20
Cr₂: 2×52.00 = 104.00 *(Chromium is 52.00 exactly in many tables)*
O₇: 7×16.00 = 112.00
Total = 78.20 + 104.00 + 112.00 = 294.20 g/mol

Wait — student wrote 294.19? Close enough — depends on Cr value.

If Cr = 51.996 ≈ 52.00, then 2×52.00 = 104.00 → total 294.20

But some sources use Cr = 51.9961 → 2×51.9961 = 103.9922 → +78.20 +112.00 = 294.1922 → rounds to 294.19

So both acceptable. We’ll use 294.19 to match precision.

Actually, let’s use more precise values:

Standard atomic weights (IUPAC 2021):

- K: 39.0983 → 2× = 78.1966
- Cr: 51.9961 → 2× = 103.9922
- O: 15.999 ×7 = 111.993
Sum: 78.1966 + 103.9922 + 111.993 = 294.1818 → 294.18 g/mol

Hmm — discrepancy.

In most high school contexts, they use:

K = 39.10, Cr = 52.00, O = 16.00 → 78.20 + 104.00 + 112.00 = 294.20

But student wrote 294.19 — perhaps using Cr = 51.99?

To avoid confusion, let’s stick with commonly used textbook values:

Assume:

K = 39.10
Cr = 52.00
O = 16.00
→ 2×39.10 = 78.20; 2×52.00 = 104.00; 7×16.00 = 112.00 → Total = 294.20

But since the student has 294.19, and many online calculators give 294.18–294.19, let’s check exact:

Using:

K: 39.0983
Cr: 51.9961
O: 15.999

K₂: 78.1966
Cr₂: 103.9922
O₇: 111.993
Sum: 78.1966 + 103.9922 = 182.1888 + 111.993 = 294.1818 → 294.18 g/mol

Rounded to two decimals: 294.18

But student wrote 294.19 — close. Maybe rounding difference.

For consistency, we'll use 294.18 as most accurate.

Wait — let’s move on and come back.

Actually, for school level, 294.20 is often accepted. But let’s be precise.

I’ll use:

K = 39.10
Cr = 52.00
O = 16.00
→ 294.20

But to match common practice, many textbooks say 294.2 g/mol.

Looking up standard value: Potassium dichromate molar mass is 294.185 g/mol → so 294.19 when rounded to two decimals.

Yes! So 294.19 g/mol is correct.

11. AgNO₃

Ag: 107.87
N: 14.01
O₃: 48.00
Total = 107.87 + 14.01 + 48.00 = 169.88 g/mol

12. BaSO₄

Ba: 137.33
S: 32.07
O₄: 64.00
Total = 137.33 + 32.07 + 64.00 = 233.40 g/mol

13. Pb(NO₃)₂

Pb: 207.20
N₂: 28.02
O₆: 96.00
Total = 207.20 + 28.02 + 96.00 = 331.22 g/mol

Wait — student wrote 331.21? Let’s check:

Pb: 207.2
N: 14.01×2 = 28.02
O: 16.00×6 = 96.00
Sum: 207.2 + 28.02 = 235.22 + 96.00 = 331.22

But if Pb = 207.19? Some tables use 207.2, others 207.19.

Standard atomic weight of Pb is 207.2 → so 331.22

But student has 331.21 — very close. Perhaps using Pb = 207.19?

207.19 + 28.02 + 96.00 = 331.21 → yes.

So depending on source, either is fine. We’ll use 331.21 to match student’s likely source.

Actually, IUPAC gives Pb as [206.14, 207.94] — no single value, but commonly 207.2.

For accuracy, let’s use:

Pb: 207.20
N: 14.007 ×2 = 28.014
O: 15.999 ×6 = 95.994
Sum: 207.20 + 28.014 = 235.214 + 95.994 = 331.208 → 331.21 g/mol

Perfect — so 331.21 g/mol

14. Na₂CO₃

Na₂: 2×22.99 = 45.98
C: 12.01
O₃: 48.00
Total = 45.98 + 12.01 + 48.00 = 105.99 g/mol

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Now, comparing to student’s answers:

From the image transcription:

1. H₂O → 18.02 ✔
2. CO₂ → 44 → should be 44.01, but acceptable
3. NO₃ → 62.01 ✔
4. CaCO₃ → 100.09 ✔
5. Al₂(SO₄)₃ → 342.17 ✔
6. (NH₄)₂SO₄ → 132.17 ✔
7. Cu(NO₃)₂ → 187.57 ✔
8. Mg(OH)₂ → 58.33 ✔
9. FeCl₃ → 162.20 ✔
10. K₂Cr₂O₇ → 294.19 ✔ (we confirmed)
11. AgNO₃ → 169.88 ✔
12. BaSO₄ → 233.40 ✔
13. Pb(NO₃)₂ → 331.21 ✔
14. Na₂CO₃ → 105.99 ✔

All student answers are correct within typical rounding!

But our task is to solve accurately — so we present the precise values.

Final Answer will list all 14 compounds with their correct molar masses.

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Final Answer:
1. H₂O: 18.02 g/mol
2. CO₂: 44.01 g/mol
3. NO₃: 62.01 g/mol
4. CaCO₃: 100.09 g/mol
5. Al₂(SO₄)₃: 342.17 g/mol
6. (NH₄)₂SO₄: 132.17 g/mol
7. Cu(NO₃)₂: 187.57 g/mol
8. Mg(OH)₂: 58.33 g/mol
9. FeCl₃: 162.20 g/mol
10. K₂Cr₂O₇: 294.19 g/mol
11. AgNO₃: 169.88 g/mol
12. BaSO₄: 233.40 g/mol
13. Pb(NO₃)₂: 331.21 g/mol
14. Na₂CO₃: 105.99 g/mol