Stoichiometry And Stoichiometric Calculations

Step 1 — Identify the mole ratio from the balanced equation

From the balanced equation: 2 Na + Cl₂ → 2 NaCl. The mole ratio between Na and NaCl is 2 mol Na : 2 mol NaCl, which simplifies to 1 : 1.

Step 2 — Convert given moles of Na to moles of NaCl

Because the stoichiometric ratio is 1:1, 2.0 moles Na will produce 2.0 moles NaCl (Cl₂ is in excess so Na is the limiting reagent).

Step 3 — Calculate the molar mass of NaCl

Use standard atomic masses (approximate): Na = 22.99 g·mol⁻¹, Cl = 35.45 g·mol⁻¹.
Molar mass of NaCl = 22.99 + 35.45 = 58.44 g·mol⁻¹.

Step 4 — Convert moles of NaCl to grams

Mass = (moles) × (molar mass) = 2.0 mol × 58.44 g·mol⁻¹ = 116.88 g.

Step 5 — Significant figures and final reporting

• The given quantity 2.0 mol has 2 significant figures. • Molar masses (22.99 and 35.45) are typically given to four significant figures, but the final result should generally reflect the least precise measured value (here 2.0 has 2 s.f.). • Therefore you may report the theoretical yield as:

• Exact (from calculation): 116.88 g
• Rounded to 3 s.f. (common): 117 g
• Rounded to 2 s.f. (consistent with 2.0 mol): 1.2 × 10² g (or 120 g)

Quick check

• Mole ratio 1:1 ⟹ moles Na = moles NaCl (2.0 mol). • 2.0 × 58.44 ≈ 116.9 g — consistent and dimensionally correct.

Given reaction:

Step 1: Use the stoichiometric relationship

The balanced equation tells us that for every 2 moles of (hydrogen), 2 moles of (water) are produced.

Step 2: Set up the proportion

From the balanced equation:

Therefore, if 4 moles of hydrogen ( ) react, the number of moles of water produced will be:

✅ Final Answer:

The number of moles of water produced is

The molar mass of water (H O) is calculated as: Now, we calculate the mass of 0.5 moles of water: Thus, the mass of 0.5 moles of water is 9 g. So, the correct answer is option (2).

We are given the following data:

• 0.5 moles of sodium (Na)
• Excess chlorine (Cl₂)

Step 1: Write the balanced chemical equation

The balanced equation is:

Step 2: Determine the moles of NaCl formed

From the balanced equation, we know that 2 moles of Na produce 2 moles of NaCl. So, 0.5 moles of Na will produce 0.5 moles of NaCl.

Step 3: Calculate the mass of NaCl

The molar mass of NaCl is:

The mass of NaCl is:

Conclusion:

The mass of sodium chloride formed is approximately .

Given: From the balanced equation, we see that: - 2 moles of hydrogen ( ) produce 2 moles of water ( ).

Use mole ratio The mole ratio between hydrogen and water is 1:1. Therefore, 4 moles of hydrogen will produce 4 moles of water.

Answer: The correct answer is option (2): 4 moles.