Unit 8 ws-1 | PDF - Free Printable

Let’s solve each problem step by step.

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Problem 1: Hydrogen sulfide + oxygen → sulfur dioxide + water

We’re told:
> “How much of oxygen gas would be needed to completely burn 8 moles of hydrogen sulfide?”

First, write the balanced equation (already given):

2 H₂S + 3 O₂ → 2 SO₂ + 2 H₂O

From the coefficients:
- 2 moles H₂S require 3 moles O₂

So for 8 moles H₂S, set up a ratio:

→ (3 moles O₂ / 2 moles H₂S) × 8 moles H₂S = ?

Calculate:
(3/2) × 8 = 12

✔ So, 12 moles of O₂ are needed.

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Problem 2: Propane combustion

Given:
C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O
If 12 moles of propane react, how many moles of products form?

Note: The question says “how many moles of products were formed?” — that means total moles of ALL products combined.

From the equation:
- 1 mole C₃H₈ → 3 moles CO₂ + 4 moles H₂O = 7 moles of products total

So for 12 moles C₃H₈:

→ 12 × 7 = 84 moles of products

But let’s check if they want individual products or total.

Looking at the worksheet layout, it has columns for CO₂ and H₂O separately under “After”, so maybe they want both values.

Re-read:
> “how many moles of products were formed?”

It doesn’t specify which product — but in context, since two products are listed, and the table has space for both, likely they want:

- Moles of CO₂ formed
- Moles of H₂O formed

From the reaction:

1 mol C₃H₈ → 3 mol CO₂ → so 12 mol C₃H₈ → 12 × 3 = 36 mol CO₂

1 mol C₃H₈ → 4 mol H₂O → so 12 mol C₃H₈ → 12 × 4 = 48 mol H₂O

Total products = 36 + 48 = 84 moles — but unless asked for total, better to report both.

However, looking at the way the worksheet is structured (“how many moles of products were formed?”), and since it's plural, and there are two products, I think they expect you to calculate both.

But wait — in Problem 1, they only asked for one thing (oxygen needed). In Problem 2, it says “products” plural — so probably list both.

Actually, rechecking the original text:

> “If 12 moles of carbon dioxide are formed...” — NO! Wait, no — reread carefully:

Original says:

> “Propane, C₃H₈, reacts with air to form carbon dioxide and water. If 12 moles of propane gas are burned, how many moles of products were formed?”

Ah — typo in my reading earlier. It says 12 moles of propane, not carbon dioxide.

So yes — 12 moles C₃H₈.

Products: CO₂ and H₂O.

Mole ratios:

CO₂: 3 per 1 C₃H₈ → 12 × 3 = 36 moles CO₂
H₂O: 4 per 1 C₃H₈ → 12 × 4 = 48 moles H₂O

So answer should be:
36 moles of CO₂ and 48 moles of H₂O

But again — does “how many moles of products” mean total? In chemistry, sometimes “products” refers to all substances produced, so total moles.

But in this case, since the worksheet has separate boxes for CO₂ and H₂O under “After”, I believe they want the amounts of each.

Wait — look at the handwritten part in the image (even though we don’t describe images, the user included it as part of the task). But per instructions, we ignore image description.

Stick to the text provided in the OCR-like transcription.

The problem says:
> “how many moles of products were formed?”

And then shows a table with “CO₂” and “H₂O” under “After”.

So safest interpretation: calculate moles of each product.

Thus:

→ CO₂: 36 moles
→ H₂O: 48 moles

But if forced to give one number, it would be 84. However, given the structure, I’ll assume they want both.

Wait — actually, in Problem 3, they ask specifically about ammonia, and give a single answer expected.

In Problem 2, since it says “products” and lists two, and the table has two slots, I think we should provide both.

But let me see the exact wording again:

> “how many moles of products were formed?”

This is ambiguous. But in most textbook problems like this, when they say “how many moles of products” and there are multiple, they often mean total moles of all products.

Example: if 1 mole makes 7 moles of products, then 12 moles make 84.

Moreover, in the change row, they might just want totals.

But to be safe, let’s do what the stoichiometry dictates.

I think the intended answer is:

For 12 moles C₃H₈:

- Moles of CO₂ = 36
- Moles of H₂O = 48

But since the question says “how many moles of products”, and doesn't specify which, perhaps they want the sum.

Wait — look at Problem 1: they asked for “how much of oxygen gas” — singular.

Problem 2: “how many moles of products” — plural.

In English, “products” could mean the collection.

But in chemistry education, when they say “how many moles of products are formed from X moles of reactant”, and there are multiple products, they usually expect you to calculate each or state total.

Given that the worksheet has spaces for both CO₂ and H₂O, I will go with calculating both.

But the final answer format requires one box. Hmm.

Perhaps I should check standard practice.

Alternative approach: in the ICE table shown in the image (which we can't reference), they have "After" for CO₂ and H₂O separately, so likely they want those values.

Since the instruction is to solve accurately, and the problem is from a worksheet with tables, I'll compute both.

But for Final Answer, I need to put something concise.

Let me see Problem 3 for clue.

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Problem 3: Ammonia synthesis

N₂ + 3 H₂ → 2 NH₃

Question: How many moles of ammonia can be made from 0.15 moles of nitrogen gas?

From equation:
1 mole N₂ → 2 moles NH₃

So 0.15 moles N₂ → 0.15 × 2 = 0.30 moles NH₃

That’s straightforward.

Now back to Problem 2.

I recall that in some curricula, when they say “moles of products”, and there are multiple, they might expect the total.

But let’s calculate based on mole ratios.

Perhaps the best way is to notice that in the reaction:

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

For every 1 mole of C₃H₈, you get 3 + 4 = 7 moles of products.

So for 12 moles C₃H₈, 12 × 7 = 84 moles of products total.

And since the question says “how many moles of products were formed?”, without specifying which, 84 is correct.

In many textbooks, this is accepted.

For example, if you burn methane: CH₄ + 2O₂ → CO₂ + 2H₂O, and ask how many moles of products from 1 mole CH₄, answer is 3 moles (1 CO₂ + 2 H₂O).

So I think for consistency, Problem 2 answer is 84 moles.

But let’s confirm with the first problem.

Problem 1 was clear: find moles of O₂ needed for 8 moles H₂S → 12 moles.

Problem 3: 0.15 moles N₂ → 0.30 moles NH₃.

Problem 2: 12 moles C₃H₈ → ? moles products.

Given that, and to match the style, I'll go with total moles of products.

So:

12 mol C₃H₈ × (7 mol products / 1 mol C₃H₈) = 84 mol products.

Yes.

To be thorough, let's see if oxygen is limiting — but the problem says "if 12 moles of propane are burned", implying complete combustion, so oxygen is in excess, and propane is limiting. So yes, products based on propane.

Final decision:

Problem 1: 12 moles O₂
Problem 2: 84 moles of products (total)
Problem 3: 0.30 moles NH₃

But for Problem 2, if they wanted individual, they would have said "how many moles of carbon dioxide and water".

Since it says "products", plural, but as a collective, 84 is fine.

I think it's safe.

Now, let's write the answers clearly.

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Final Answer:
1. 12 moles of O₂
2. 84 moles of products
3. 0.30 moles of NH₃