Mole calculations worksheet|KS4 Chemistry|Teachit - Free Printable

Let's solve both Task 1 and Task 2 step by step. We’ll use the periodic table to find the atomic masses of each element (in g/mol). Then we'll apply the formula:

Key Formula:

- Mass (g) = Moles × Molar Mass (g/mol)
- Moles = Mass (g) ÷ Molar Mass (g/mol)

---

## 🔹 Task 1: Find the mass of each of the following

We'll use the molar masses from the periodic table:

| Element | Molar Mass (g/mol) |
|--------|---------------------|
| C | 12.01 |
| Na | 22.99 |
| Mg | 24.31 |
| Au | 197.0 |
| Si | 28.09 |
| Br | 79.90 |
| P | 30.97 |
| Fe | 55.85 |

---

a) 5 moles of carbon (C) atoms

Mass = 5 mol × 12.01 g/mol = 60.05 g

b) 3 moles of sodium (Na) atoms

Mass = 3 mol × 22.99 g/mol = 68.97 g

c) 2.5 moles of magnesium (Mg) atoms

Mass = 2.5 mol × 24.31 g/mol = 60.775 g

d) 6 moles of gold (Au) atoms

Mass = 6 mol × 197.0 g/mol = 1182 g

e) 0.8 moles of silicon (Si) atoms

Mass = 0.8 mol × 28.09 g/mol = 22.472 g

f) 0.5 moles of bromine (Br) atoms

Mass = 0.5 mol × 79.90 g/mol = 39.95 g

g) 1.5 moles of phosphorus (P) atoms

Mass = 1.5 mol × 30.97 g/mol = 46.455 g

h) 2 moles of iron (Fe) atoms

Mass = 2 mol × 55.85 g/mol = 111.7 g

---

✔ Task 1 Answers:

| Question | Answer (g) |
|--------|------------------|
| a | 60.05 |
| b | 68.97 |
| c | 60.775 |
| d | 1182 |
| e | 22.472 |
| f | 39.95 |
| g | 46.455 |
| h | 111.7 |

---

## 🔹 Task 2: How many moles are there in each?

Use:
Moles = Mass (g) ÷ Molar Mass (g/mol)

| Element | Molar Mass (g/mol) |
|--------|---------------------|
| Mg | 24.31 |
| Ne | 20.18 |
| Cu | 63.55 |
| Ag | 107.87 |
| He | 4.00 |
| Li | 6.94 |
| H | 1.01 |
| Ca | 40.08 |

---

a) 48 g of magnesium (Mg)

Moles = 48 ÷ 24.31 ≈ 1.974 moles

b) 80 g of neon (Ne)

Moles = 80 ÷ 20.18 ≈ 3.963 moles

c) 128 g of copper (Cu)

Moles = 128 ÷ 63.55 ≈ 2.015 moles

d) 324 g of silver (Ag)

Moles = 324 ÷ 107.87 ≈ 3.004 moles

e) 14 g of helium (He)

Moles = 14 ÷ 4.00 = 3.5 moles

f) 3.5 g of lithium (Li)

Moles = 3.5 ÷ 6.94 ≈ 0.504 moles

g) 0.2 g of hydrogen (H)

Moles = 0.2 ÷ 1.01 ≈ 0.198 moles

h) 100 g of calcium (Ca)

Moles = 100 ÷ 40.08 ≈ 2.495 moles

---

✔ Task 2 Answers:

| Question | Answer (moles) |
|--------|------------------|
| a | 1.974 |
| b | 3.963 |
| c | 2.015 |
| d | 3.004 |
| e | 3.5 |
| f | 0.504 |
| g | 0.198 |
| h | 2.495 |

---

## ✔ Final Answers Summary

Task 1 – Masses (in grams):

a) 60.05
b) 68.97
c) 60.775
d) 1182
e) 22.472
f) 39.95
g) 46.455
h) 111.7

Task 2 – Moles:

a) 1.974
b) 3.963
c) 2.015
d) 3.004
e) 3.5
f) 0.504
g) 0.198
h) 2.495

---

💡 Tips for Accuracy:
- Always use precise atomic masses from the periodic table.
- Round appropriately based on significant figures (e.g., 3.5 g has 2 sig figs → answer should have 2 sig figs).
- Remember: 1 mole = molar mass in grams.

Let me know if you'd like this formatted as a printable answer sheet!