Chemistry worksheet designed to test students' understanding of the Law of Conservation of Mass through various calculation and balancing problems.

It looks like you've uploaded a worksheet titled "Conservation of Mass" that includes several chemistry problems related to balancing chemical equations, identifying reactants and products, and applying the law of conservation of mass. Since I can't view images directly, I’ll help you solve each problem based on the text you’ve provided.

Let’s go through each question one by one and solve it step-by-step.

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1. Balance the chemical equations below. Determine each product and write each reaction.

#### a)
2 CuO + 2 NaOH → Cu(OH)₂ + Na₂O₂

Wait — this equation is not balanced and may be incorrect. Let's check:

- Left: Cu = 2, O = 2 (from CuO) + 2 (from NaOH) = 4, Na = 2, H = 2
- Right: Cu = 1 (in Cu(OH)₂), O = 2 (in OH) + 2 (in Na₂O₂) = 4? Wait — Na₂O₂ is sodium peroxide, which has two oxygen atoms.

But let's look at the actual chemistry:
- Copper(II) oxide (CuO) reacts with sodium hydroxide (NaOH)? That’s not a typical reaction.
- More likely, this is meant to be a double displacement or precipitation reaction, but CuO is insoluble and doesn’t react with NaOH easily.

Actually, a common reaction involving CuO and NaOH isn't standard. Perhaps there's a typo.

Alternatively, maybe it's supposed to be CuCl₂ + 2NaOH → Cu(OH)₂↓ + 2NaCl, but here it's written as CuO.

Let’s assume the equation is:
> CuO + 2NaOH → Cu(OH)₂ + Na₂O — but this isn't correct either because Na₂O is unstable in water.

Wait — perhaps it's a hydrolysis or formation of copper hydroxide?

But CuO is not soluble, so it won't react with NaOH.

So maybe the intended reaction is:
> CuSO₄ + 2NaOH → Cu(OH)₂↓ + Na₂SO₄

But given what's written:
2 CuO + 2 NaOH → Cu(OH)₂ + Na₂O₂

This seems chemically incorrect. Let’s try balancing it as written:

Left:
- Cu: 2
- O: 2 (from CuO) + 2 (from NaOH) = 4
- Na: 2
- H: 2

Right:
- Cu(OH)₂: Cu=1, O=2, H=2
- Na₂O₂: Na=2, O=2

Total right: Cu=1, O=4, H=2, Na=2

So Cu is unbalanced (2 left, 1 right). So we need 2 Cu(OH)₂.

Try:
> 2 CuO + 2 NaOH → 2 Cu(OH)₂ + Na₂O₂

Now:
Left: Cu=2, O=2+2=4, Na=2, H=2
Right: Cu=2, O=4 (from 2×OH) + 2 (from Na₂O₂) = 6? No — wait: each Cu(OH)₂ has 2 O and 2 H, so 2 Cu(OH)₂ has 4 O and 4 H.

Na₂O₂ has 2 O.

So total O = 4 + 2 = 6 → too many.

Also H: left = 2, right = 4 → imbalance.

This suggests the reaction is not valid as written.

✔ Likely mistake: The correct reaction might be:
> CuSO₄ + 2NaOH → Cu(OH)₂↓ + Na₂SO₄

But since the original says CuO + NaOH, perhaps it's a different context.

Alternatively, CuO does not react with NaOH under normal conditions.

➡️ Conclusion: This equation appears to be incorrect or miswritten.

Let’s skip and move to the next.

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#### b)
C₂H₄ + O₂ → CO₂ + H₂O

Balance this combustion reaction.

Unbalanced:
> C₂H₄ + O₂ → CO₂ + H₂O

Step-by-step:

1. Carbon: 2 on left → need 2 CO₂ on right
2. Hydrogen: 4 on left → need 2 H₂O (since each has 2 H)
3. Now check oxygen:
- Right: 2 CO₂ → 4 O; 2 H₂O → 2 O → total 6 O
- Left: O₂ → need 3 O₂ molecules

So:
> C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

✔ Balanced.

Products: Carbon dioxide (CO₂) and water (H₂O)

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#### c)
2N₂ + 3H₂ → NH₃

This is the Haber process.

Unbalanced: N₂ + H₂ → NH₃

Balance:
- N: 2 on left → need 2 NH₃ on right
- H: 6 on right → need 3 H₂ on left

So:
> N₂ + 3H₂ → 2NH₃

But the given equation is:
> 2N₂ + 3H₂ → NH₃

That’s wrong.

Left: N = 4, H = 6
Right: N = 1, H = 3 → unbalanced.

So correct balanced equation:
> N₂ + 3H₂ → 2NH₃

But if you want 2N₂, then:
> 2N₂ + 6H₂ → 4NH₃

So the original is incorrect.

✔ Corrected: N₂ + 3H₂ → 2NH₃

Product: Ammonia (NH₃)

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2. How do you know if a compound is a product or reactant in a chemical reaction? Explain your answer.

👉 Answer:
In a chemical reaction, reactants are the substances present before the reaction starts, and they are written on the left side of the arrow (→).
Products are the new substances formed after the reaction, and they are written on the right side of the arrow.

For example:
A + B → C + D
- A and B are reactants
- C and D are products

You can also tell by observing changes: reactants are consumed, and products are formed.

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3. Use the reaction below and the masses of several of the reactants and products. Fill in the table with the correct mass. Show your work on the back of your sheet.

Reaction:
Fe + S → FeS

Given:
- Mass of Fe = 50.0 g
- Mass of S = 30.0 g
- Mass of FeS = ?

We use Law of Conservation of Mass:
Mass of reactants = Mass of products

So:
> Mass of FeS = Mass of Fe + Mass of S = 50.0 g + 30.0 g = 80.0 g

| Reactant | Mass (g) |
|---------|----------|
| Fe | 50.0 |
| S | 30.0 |
| FeS | 80.0 |

✔ Answer: 80.0 g

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4. Balance the following equation.

6 Mg(OH)₂ + 3Cl₂ → 6MgCl₂ + 3O₂ + 6H₂O

Check balance:

Left:
- Mg: 6
- O: 6×2 = 12 from OH, plus 6×1 = 6 from H₂O? Wait — no, it's only Mg(OH)₂ and Cl₂

Wait — Mg(OH)₂ has:
- Mg: 6
- O: 6×2 = 12
- H: 6×2 = 12
- Cl₂: 3 → Cl: 6

Right:
- MgCl₂: 6 → Mg:6, Cl:12 → wait! Cl: 6×2 = 12 → but left has only 6 Cl from 3 Cl₂ → mismatch

So this is unbalanced.

Let’s fix it.

The reaction is likely:
> Mg(OH)₂ + Cl₂ → MgCl₂ + H₂O + O₂

But chlorine doesn’t oxidize hydroxide directly like this.

Actually, chlorine gas can oxidize hydroxide ions in basic solution to form chloride and chlorate:

> 3Cl₂ + 6OH⁻ → 5Cl⁻ + ClO₃⁻ + 3H₂O

But here it's written as Mg(OH)₂ and Cl₂ forming MgCl₂, O₂, H₂O — that’s unusual.

Let’s suppose:
> Mg(OH)₂ + Cl₂ → MgCl₂ + H₂O + O₂

Try balancing:

Start with:
> Mg(OH)₂ + Cl₂ → MgCl₂ + H₂O + O₂

Left: Mg=1, O=2, H=2, Cl=2
Right: Mg=1, Cl=2, H=2, O=1 (H₂O) + 2 (O₂) = 3 → O imbalance

Need more H₂O?

Try:
> 2Mg(OH)₂ + Cl₂ → 2MgCl₂ + 2H₂O + O₂

Now:
Left: Mg=2, O=4, H=4, Cl=2
Right: Mg=2, Cl=4 → wait! MgCl₂ has 2 Cl per molecule → 2MgCl₂ = 4 Cl → but left has only 2 Cl → imbalance

So need 2 Cl₂ → 4 Cl

Try:
> 2Mg(OH)₂ + 2Cl₂ → 2MgCl₂ + 2H₂O + O₂

Left: Mg=2, O=4, H=4, Cl=4
Right: Mg=2, Cl=4, H=4, O=2 (H₂O) + 2 (O₂) = 4 → O=4 ✔

Yes!

So balanced:
> 2Mg(OH)₂ + 2Cl₂ → 2MgCl₂ + 2H₂O + O₂

But the original says:
> 6 Mg(OH)₂ + 3Cl₂ → 6MgCl₂ + 3O₂ + 6H₂O

Check that:
Left: Mg=6, O=12, H=12, Cl=6
Right: Mg=6, Cl=12 → ✘ Cl: 6 vs 12 → unbalanced

So correct version should be:
> 6Mg(OH)₂ + 6Cl₂ → 6MgCl₂ + 6H₂O + 3O₂

Because:
- Cl: 6Cl₂ = 12 Cl → 6MgCl₂ = 12 Cl ✔
- Mg: 6 ✔
- H: 12 → 6H₂O = 12 H ✔
- O: left: 6×2 = 12 O from OH → right: 6H₂O = 6 O, 3O₂ = 6 O → total 12 O ✔

✔ Balanced equation:
> 6Mg(OH)₂ + 6Cl₂ → 6MgCl₂ + 6H₂O + 3O₂

But the original has 3Cl₂, which is half — so it’s unbalanced.

So correct answer:
6Mg(OH)₂ + 6Cl₂ → 6MgCl₂ + 6H₂O + 3O₂

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5. Your lab partner has a volcano model container that holds 100 mL of liquid. Suppose that you pour 50 mL of water into it. Then you add 25 mL of vinegar and 25 mL of baking soda solution. What is the maximum volume of liquid that can be in the container? Will the mixture spill over? Explain your answer.

Total volume added:
- Water: 50 mL
- Vinegar: 25 mL
- Baking soda solution: 25 mL
→ Total = 50 + 25 + 25 = 100 mL

Container capacity: 100 mL

So maximum volume = 100 mL

But when baking soda and vinegar mix, they react:
> NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂↑

Gas (CO₂) is produced → volume increases due to gas bubbles

Even though liquid volume is 100 mL, gas occupies space, so the total volume exceeds 100 mL → it will overflow

✔ Answer:
The mixture will spill over because the reaction produces carbon dioxide gas, which increases the total volume beyond the container’s capacity.

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6. What is the law of conservation of mass? In NO way does a definition from your textbook. Explain the law in your own words. It can be written in a paragraph or as a short answer.

👉 Answer:
The law of conservation of mass means that in a chemical reaction, matter cannot be created or destroyed. The total mass of the substances before the reaction (reactants) is equal to the total mass after the reaction (products). Atoms are rearranged to form new substances, but none are lost or gained. For example, if you burn wood, the mass of the ash, smoke, and gases equals the mass of the wood and oxygen used — even though it looks like some material disappears, it's just changed form.

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✔ Final Summary of Answers:

1. a) Equation likely incorrect. Possibly meant to be CuSO₄ + 2NaOH → Cu(OH)₂ + Na₂SO₄
b) C₂H₄ + 3O₂ → 2CO₂ + 2H₂O (products: CO₂, H₂O)
c) N₂ + 3H₂ → 2NH₃ (product: NH₃)

2. Reactants are on the left, products on the right of the arrow.

3. Mass of FeS = 50.0 + 30.0 = 80.0 g

4. Balanced: 6Mg(OH)₂ + 6Cl₂ → 6MgCl₂ + 6H₂O + 3O₂

5. Total liquid volume = 100 mL, but gas forms → spills over

6. Matter is neither created nor destroyed in a chemical reaction; total mass stays constant.

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