Unit 2 Molar Mass Worksheet | Study notes Chemistry | Docsity - Free Printable

Explanation:
To calculate the molar mass of a chemical, you add up the atomic masses of all the atoms in its formula. Use standard atomic masses (rounded to two decimal places, as commonly taught in high school chemistry):

- H = 1.01 g/mol
- C = 12.01 g/mol
- N = 14.01 g/mol
- O = 16.00 g/mol
- F = 19.00 g/mol
- Mg = 24.31 g/mol
- P = 30.97 g/mol
- S = 32.07 g/mol
- Cl = 35.45 g/mol
- K = 39.10 g/mol
- Fe = 55.85 g/mol
- Be = 9.01 g/mol
- B = 10.81 g/mol
- U = 238.03 g/mol
- Pb = 207.2 g/mol
- Ga = 69.72 g/mol

Now compute each one carefully:

1) Cl₂: 2 × 35.45 = 70.90 g/mol
2) KOH: K (39.10) + O (16.00) + H (1.01) = 56.11 g/mol
3) BeCl₂: Be (9.01) + 2×Cl (2×35.45 = 70.90) = 79.91 g/mol
4) FeCl₃: Fe (55.85) + 3×Cl (3×35.45 = 106.35) = 162.20 g/mol
5) BF₃: B (10.81) + 3×F (3×19.00 = 57.00) = 67.81 g/mol
6) CCl₂F₂: C (12.01) + 2×Cl (2×35.45 = 70.90) + 2×F (2×19.00 = 38.00) = 120.91 g/mol
7) Mg(OH)₂: Mg (24.31) + 2×O (2×16.00 = 32.00) + 2×H (2×1.01 = 2.02) = 58.33 g/mol
8) UF₆: U (238.03) + 6×F (6×19.00 = 114.00) = 352.03 g/mol
9) SO₂: S (32.07) + 2×O (2×16.00 = 32.00) = 64.07 g/mol
10) H₃PO₄: 3×H (3×1.01 = 3.03) + P (30.97) + 4×O (4×16.00 = 64.00) = 98.00 g/mol
11) (NH₄)₂SO₄:
- NH₄⁺ has N (14.01) + 4×H (4×1.01 = 4.04) = 18.05 per NH₄
- Two NH₄ = 2×18.05 = 36.10
- Plus S (32.07) + 4×O (64.00)
- Total = 36.10 + 32.07 + 64.00 = 132.17 g/mol
12) CH₃COOH (acetic acid):
- Formula is C₂H₄O₂
- 2×C = 2×12.01 = 24.02
- 4×H = 4×1.01 = 4.04
- 2×O = 2×16.00 = 32.00
- Total = 24.02 + 4.04 + 32.00 = 60.06 g/mol
13) Pb(NO₃)₂:
- Pb = 207.2
- NO₃⁻ = N (14.01) + 3×O (48.00) = 62.01
- Two NO₃ = 2×62.01 = 124.02
- Total = 207.2 + 124.02 = 331.22 g/mol
14) Ga₂(SO₃)₃:
- Ga₂: 2×69.72 = 139.44
- SO₃: S (32.07) + 3×O (48.00) = 80.07
- Three SO₃: 3×80.07 = 240.21
- Total = 139.44 + 240.21 = 379.65 g/mol

Let me double-check a few tricky ones:

- (NH₄)₂SO₄: N = 2×14.01 = 28.02; H = 8×1.01 = 8.08; S = 32.07; O = 4×16.00 = 64.00 → 28.02+8.08+32.07+64.00 = 132.17 ✔
- Ga₂(SO₃)₃: Ga₂ = 139.44; S₃ = 3×32.07 = 96.21; O₉ = 9×16.00 = 144.00 → 139.44+96.21+144.00 = 379.65 ✔
- CH₃COOH is indeed C₂H₄O₂ → 60.06 ✔

All values are consistent with standard molar mass calculations.

Final Answer:
1) 70.90 g/mol
2) 56.11 g/mol
3) 79.91 g/mol
4) 162.20 g/mol
5) 67.81 g/mol
6) 120.91 g/mol
7) 58.33 g/mol
8) 352.03 g/mol
9) 64.07 g/mol
10) 98.00 g/mol
11) 132.17 g/mol
12) 60.06 g/mol
13) 331.22 g/mol
14) 379.65 g/mol