Balancing Act worksheet for learning how to balance chemical equations.

Let’s solve each equation step by step. We’ll balance them so that the number of atoms of each element is the same on both sides.

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1) Mg + O₂ → MgO

Left side:
- Mg = 1
- O = 2

Right side:
- Mg = 1
- O = 1

→ Oxygen is unbalanced. Let’s put a 2 in front of MgO to make oxygen = 2 on right:

Mg + O₂ → 2MgO

Now right side has:
- Mg = 2
- O = 2

Left side still has Mg = 1 → so put 2 in front of Mg:

2Mg + O₂ → 2MgO

✔ Balanced!

Answer for #1:
Mg = 2, O = 1 (in O₂, it's already 2 atoms — we don’t change subscript), Mg in product = 2

Wait — let’s read the question again.

It says: “Balance each of these for each atom” and gives blanks like:

Mg = ___
O = ___
Mg = ___
O = ___

Looking at the layout:

They probably want:

For reactants:
Mg = ?
O = ?

For products:
Mg = ?
O = ?

So for balanced equation: 2Mg + O₂ → 2MgO

Reactants:
Mg = 2
O = 2 (from O₂)

Products:
Mg = 2 (from 2MgO)
O = 2 (from 2MgO)

But wait — in the original problem, they wrote:

“Mg + __ O₂ → __ MgO”

And then below:

Mg = ___
O = ___
Mg = ___
O = ___

Probably meaning:

First blank after Mg is coefficient for O₂ → should be 1? But we need to balance.

Actually, looking at their format:

They have:

Mg + __ O₂ → __ MgO

Then:

Mg = ___
O = ___
Mg = ___
O = ___

I think they mean:

After balancing, what are the coefficients or atom counts?

Wait — no, look at instruction:

“a) Balance number of atoms for each atom”

Then they list:

Mg = ___
O = ___
Mg = ___
O = ___

This likely means:

On left side: how many Mg atoms? How many O atoms?

On right side: how many Mg atoms? How many O atoms?

But in the unbalanced form, it’s written as:

Mg + __ O₂ → __ MgO

So we fill in the blanks with coefficients first.

Standard way: we add coefficients to balance.

So for:

Mg + O₂ → MgO

We found: 2Mg + O₂ → 2MgO

So coefficients:

In front of Mg: 2
In front of O₂: 1 (usually not written, but implied)
In front of MgO: 2

But the worksheet has:

Mg + __ O₂ → __ MgO

So we write:

Mg + 1 O₂ → 2 MgO? No — because then Mg is 1 on left, 2 on right.

Actually, we must also put coefficient in front of Mg.

The way it’s written: “Mg + __ O₂ → __ MgO” — this implies we can only fill the blanks shown.

But that would be incorrect unless we assume we can add coefficient to Mg too.

Looking back at instructions:

“b) Pick an element that is not equal on both sides... Add a coefficient in front...”

So yes, we can add coefficients anywhere.

In the space given, they have:

Mg + __ O₂ → __ MgO

But we need to put a 2 in front of Mg as well. Probably the worksheet expects us to understand that.

Perhaps the blanks are only for the ones shown, but we adjust all.

To avoid confusion, let’s follow standard balancing.

Balanced equation: 2Mg + O₂ → 2MgO

So:

Atoms on left:
Mg: 2
O: 2

Atoms on right:
Mg: 2
O: 2

So for the blanks under #1:

Mg = 2 (left)
O = 2 (left)
Mg = 2 (right)
O = 2 (right)

But the worksheet might expect the coefficients inserted in the equation.

Looking at the "Try these" section, they have similar format.

For example: Ca + O₂ → CaO

We’ll do that next.

Perhaps for #1, since it’s partially filled, we complete the coefficients.

Original: Mg + __ O₂ → __ MgO

We need: 2Mg + 1O₂ → 2MgO

But usually we don’t write 1, so perhaps just fill the blanks as 1 and 2? But then Mg is unbalanced.

I think there’s a mistake in interpretation.

Let me read the instruction again:

“1) Balance number of atoms for each atom”

Then it shows:

Mg + __ O₂ → __ MgO

Then below:

Mg = ___
O = ___
Mg = ___
O = ___

I believe the four blanks are for the atom counts after balancing.

So after balancing 2Mg + O₂ → 2MgO:

Left: Mg=2, O=2
Right: Mg=2, O=2

So:

Mg = 2
O = 2
Mg = 2
O = 2

But that seems redundant. Perhaps they want the coefficients used.

Another possibility: the first two blanks are for reactant coefficients, last two for product.

But Mg doesn't have a blank before it.

Looking at the image description, it's text-based, so I'll go with standard practice.

Let’s move to the "Try these" which are clearer.

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Try these:

a) Ca + O₂ → CaO

Left: Ca=1, O=2
Right: Ca=1, O=1

Oxygen unbalanced. Put 2 in front of CaO:

Ca + O₂ → 2CaO

Now right: Ca=2, O=2
Left: Ca=1, O=2 → Ca unbalanced.

Put 2 in front of Ca:

2Ca + O₂ → 2CaO

✔ Balanced.

Coefficients: Ca=2, O₂=1, CaO=2

Atom counts:

Left: Ca=2, O=2
Right: Ca=2, O=2

So for the blanks:

Ca = 2 (left)
O = 2 (left)
Ca = 2 (right)
O = 2 (right)

But the worksheet has:

Ca = ___
O = ___
Ca = ___
O = ___

Same as above.

b) N₂ + H₂ → NH₃

Left: N=2, H=2
Right: N=1, H=3

Not balanced.

Find LCM for H: 2 and 3 → 6

So make H=6 on both sides.

Put 3 in front of H₂ → H=6
Put 2 in front of NH₃ → N=2, H=6

Left: N₂ has N=2, H₂×3 has H=6
Right: 2NH₃ has N=2, H=6

So: N₂ + 3H₂ → 2NH₃

✔ Balanced.

Atom counts:

Left: N=2, H=6
Right: N=2, H=6

Blanks:

N = 2
H = 6
N = 2
H = 6

c) Fe₂O₃ + C → Fe + CO₂

Left: Fe=2, O=3, C=1
Right: Fe=1, C=1, O=2

Unbalanced.

Start with Fe: left has 2, right has 1 → put 2 in front of Fe:

Fe₂O₃ + C → 2Fe + CO₂

Now Fe: 2=2 good
O: left=3, right=2 (from CO₂) → not good
C: left=1, right=1 good

Need to balance O. Left has 3 O, right has 2 per CO₂.

LCM of 3 and 2 is 6.

So make O=6 on both sides.

Put 2 in front of Fe₂O₃ → Fe=4, O=6
Put 3 in front of CO₂ → C=3, O=6

Now left: Fe=4, O=6, C=1
Right: Fe=2 (from earlier? Wait, we changed)

After putting 2 Fe₂O₃:

2Fe₂O₃ + C → ? Fe + ? CO₂

Fe: left=4, so right need 4 Fe → put 4 in front of Fe

O: left=6, so right need 6 O → each CO₂ has 2 O, so 3 CO₂ → C=3

So C on left is 1, but right needs 3 → put 3 in front of C

So: 2Fe₂O₃ + 3C → 4Fe + 3CO₂

Check:

Left: Fe=4, O=6, C=3
Right: Fe=4, C=3, O=6

✔ Balanced.

Atom counts:

Left: Fe=4, O=6, C=3
Right: Fe=4, C=3, O=6

But the worksheet has:

Fe = ___
O = ___
C = ___
Fe = ___
C = ___
O = ___

Six blanks, probably:

Left: Fe, O, C
Right: Fe, C, O

So:

Fe = 4
O = 6
C = 3
Fe = 4
C = 3
O = 6

d) H₂O₂ → H₂O + O₂

Left: H=2, O=2
Right: H=2, O=1 (from H₂O) + O=2 (from O₂) → total O=3? Wait no.

H₂O has H=2, O=1
O₂ has O=2
So right: H=2, O=1+2=3

Left: H=2, O=2

Unbalanced.

Common reaction: decomposition of hydrogen peroxide.

Usually: 2H₂O₂ → 2H₂O + O₂

Check:

Left: H=4, O=4
Right: 2H₂O → H=4, O=2; O₂ → O=2; total O=4

Yes.

So: 2H₂O₂ → 2H₂O + O₂

Atom counts:

Left: H=4, O=4
Right: H=4 (from 2H₂O), O=2 (from 2H₂O) + 2 (from O₂) = 4

Blanks:

H = 4
O = 4
H = 4
O = 4

But the worksheet has:

H = ___
O = ___
H = ___
O = ___

Four blanks, so likely left H, left O, right H, right O.

Yes.

Now back to #1.

For consistency, in #1: Mg + O₂ → MgO

Balanced: 2Mg + O₂ → 2MgO

So:

Left: Mg=2, O=2
Right: Mg=2, O=2

Thus:

Mg = 2
O = 2
Mg = 2
O = 2

Even though in the equation it's written without coefficient for Mg, we assume we add it.

Perhaps the worksheet intends for us to fill the coefficients in the equation first.

But since the blanks are for atom counts, we'll go with that.

Final Answers:

#1)
Mg = 2
O = 2
Mg = 2
O = 2

Try a)
Ca = 2
O = 2
Ca = 2
O = 2

Try b)
N = 2
H = 6
N = 2
H = 6

Try c)
Fe = 4
O = 6
C = 3
Fe = 4
C = 3
O = 6

Try d)
H = 4
O = 4
H = 4
O = 4

But let's double-check try c.

In try c: Fe₂O₃ + C → Fe + CO₂

We have 2Fe₂O₃ + 3C → 4Fe + 3CO₂

Left: Fe=4, O=6, C=3
Right: Fe=4, C=3, O=6 (since 3CO₂ has 3*2=6 O)

Yes.

Sometimes people write it differently, but this is correct.

For try d: 2H₂O₂ → 2H₂O + O₂

Left: H=4, O=4
Right: 2H₂O has H=4, O=2; O₂ has O=2; total O=4

Yes.

Now, for the initial part, the fill-in-the-blank at top:

"Atoms are not ______ or ______ during a chemical reaction."

Should be: created or destroyed

"Scientists know that there must be the ______ number of atoms on each ______ of the ______."

Must be: same, side, equation

"To balance the chemical equation, you must add ______ in front of the chemical formulas in the equation. You cannot ______ or ______ subscripts!"

Add: coefficients
Cannot: change or alter (probably "change" and "delete" or something, but standard is "change")

Typically: "you must add coefficients... you cannot change or delete subscripts"

But common phrasing: "cannot change the subscripts"

So likely: "change" and "alter" or "modify"

But in many texts: "cannot change the subscripts"

Perhaps: "add" and "remove" but I think "change" is key.

Standard answer: coefficients; change; delete (or alter)

But let's see.

Commonly: "add coefficients", "cannot change subscripts"

So blanks:

Atoms are not created or destroyed...

...must be the same number of atoms on each side of the equation.

...add coefficients ... cannot change or alter subscripts. (sometimes "delete")

But "alter" might be acceptable.

In some versions: "cannot change the subscripts"

So perhaps two words: "change" and "delete"

I think "change" is sufficient, but there are two blanks.

Upon recall: typical phrase is "you cannot change or remove subscripts"

Or "change or alter"

I'll go with "change" and "alter"

But to be precise, let's think.

In chemistry education, it's often: "you cannot change the subscripts, only the coefficients"

So for two blanks, perhaps "change" and "delete"

I found online sources say: "cannot change or eliminate subscripts"

But for simplicity, I'll use "change" and "alter"

Actually, standard is: "cannot change the subscripts"

Since two blanks, maybe "change" and "modify"

I think it's safe to say:

First blank: created
Second: destroyed
Third: same
Fourth: side
Fifth: equation
Sixth: coefficients
Seventh: change
Eighth: alter (or delete)

But let's confirm with logic.

The law of conservation of mass: atoms are neither created nor destroyed.

Same number on each side of the equation.

Add coefficients to balance.

Cannot change subscripts because that changes the compound.

So seventh and eighth: probably "change" and "delete" or "alter"

I'll use "change" and "alter" as it's common.

Some say "change or remove"

But "alter" is fine.

Now for the answers.

Since the user didn't specify to explain, and options are false, I'll provide final answer directly.

But the response format requires Final Answer section.

Also, for the equations, I need to present clearly.

Perhaps list all.

Since it's homework, I'll write the completed parts.

Final Answer:

Top fill-ins:
Atoms are not created or destroyed during a chemical reaction.
Scientists know that there must be the same number of atoms on each side of the equation.
To balance the chemical equation, you must add coefficients in front of the chemical formulas in the equation. You cannot change or alter subscripts!

#1)
Mg = 2
O = 2
Mg = 2
O = 2

Try a)
Ca = 2
O = 2
Ca = 2
O = 2

Try b)
N = 2
H = 6
N = 2
H = 6

Try c)
Fe = 4
O = 6
C = 3
Fe = 4
C = 3
O = 6

Try d)
H = 4
O = 4
H = 4
O = 4

Note: For #1, although the equation is written as "Mg + __ O₂ → __ MgO", the balanced form requires coefficient 2 for Mg, so atom counts are based on 2Mg + O₂ → 2MgO.

Similarly for others.

I think this is correct.