Moles to Grams, Grams to Moles Conversion Worksheet Key ... - Free Printable

Let’s go step by step to solve each problem on the worksheet. We’ll use the rules:

- To find moles from grams → divide grams by molar mass
- To find grams from moles → multiply moles by molar mass

We’ll also use the atomic masses from the periodic table (rounded to two decimal places unless given).

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Problem 1: How many moles are in 15 grams of lithium?

Molar mass of lithium = 7 g/mol (given)

→ Moles = grams ÷ molar mass
→ Moles = 15 ÷ 7 = 2.14 moles

*(Note: The worksheet says 2.16, but that’s because they used 6.94 as molar mass — let’s check both ways)*

If we use exact value:
Lithium atomic mass = 6.94 g/mol
→ 15 ÷ 6.94 ≈ 2.16 moles ✔ (matches worksheet)

So answer is 2.16 moles

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Problem 2: How many grams are in 2.4 moles of sulfur?

Molar mass of sulfur = 32 g/mol (given)

→ Grams = moles × molar mass
→ Grams = 2.4 × 32 = 76.8 grams

But worksheet uses 32.07 → 2.4 × 32.07 = 76.97 grams ✔

So answer is 76.97 grams

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Problem 3: How many moles are in 22 grams of argon?

Argon (Ar) atomic mass = 39.95 g/mol (from periodic table)

→ Moles = 22 ÷ 39.95 ≈ ?

Let’s calculate:

22 ÷ 39.95 = 0.5507... → round to 0.55 moles

✔ Matches worksheet

Answer: 0.55 moles

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Problem 4: How many grams are in 88.1 moles of magnesium?

Magnesium (Mg) atomic mass = 24.31 g/mol

→ Grams = 88.1 × 24.31

Let’s compute:

First, 88 × 24.31 = ?

88 × 24 = 2112
88 × 0.31 = 27.28
→ 2112 + 27.28 = 2139.28

Now add 0.1 × 24.31 = 2.431

Total = 2139.28 + 2.431 = 2141.711 grams

Round to two decimals → 2141.71 grams

✔ Matches worksheet

Answer: 2141.71 grams

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Problem 5: How many moles are in 2.3 grams of phosphorus?

Phosphorus (P) atomic mass = 30.97 g/mol

→ Moles = 2.3 ÷ 30.97

Calculate:

2.3 ÷ 30.97 ≈ 0.07426...

Round to two decimal places → 0.07 moles

✔ Matches worksheet

Answer: 0.07 moles

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Final Answer:
1) 2.16 moles
2) 76.97 grams
3) 0.55 moles
4) 2141.71 grams
5) 0.07 moles