Chemistry · Solutions and pH

Concentration and Dilution

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Wrap-up

What you learned

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Read next: Solubility and SaturationSee when concentration hits a capacity limit

Key takeaway

Concentration compares how much solute is present with how much liquid is available.
Adding solvent can lower concentration without removing any solute.
Adding solute at fixed volume raises concentration for a different reason than dilution lowers it.

Common misconception

Dilution means the solute disappears or leaves the beaker.

A fuller beaker can simply contain more solvent, so the same solute is spread out more.

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Carry the same beaker story into dissolving limits and visible saturationSolutions and pH

Solubility and Saturation

Keep dissolved amount, excess solid, and current capacity in one beaker so saturation reads like a visible limit instead of a slogan.

Builds on thisSolutions and pH

Acid-Base / pH Intuition

Keep acid amount, base amount, water, and the pH strip visible together so acidity and basicity stay intuitive rather than memorized.

Next in Buffer reserve and neutralizationSolutions and pH

Buffers and Neutralization

Keep neutralization, buffer reserve, and the pH strip visible together so steady pH does not look like unchanged chemistry.

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Equation snapshotConcentration from amount and volume · Dilution keeps solute fixedShow 2 equations

Concentration from amount and volume
$c = \frac{n}{V}$
Use it as a reading rule: the same solute is less concentrated when it is spread through more liquid.
Dilution keeps solute fixed
$n_{after} = n_{before}$
During dilution, the solute amount stays the same while the solvent volume increases.

Why it behaves this way

Explanation

Concentration is not just about how full the beaker looks. It tells you how much solute is present for a given amount of liquid. This bench keeps the particle view, amount-volume guide, and concentration readout together so you can connect the number to what the mixture looks like.

Dilution means adding more solvent while keeping the solute amount the same. That spreads the same dissolved particles through more liquid, so concentration falls. Adding solute can also change concentration, but for a different reason: there is more dissolved material, not just more liquid around it.

Key ideas

01Concentration compares solute amount with liquid volume.

02Dilution lowers concentration by increasing solvent volume while keeping the solute amount fixed.

03Adding solute can also change concentration, but that is not the same process as dilution.

Worked examples

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Frozen walkthrough

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Frozen walkthrough

Use the live beaker to decide what is changing: solute amount, solvent volume, or both.

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Frozen valuesUsing frozen parameters

For the current mixture, what makes the concentration high or low?

n

Solute amount

V

Solvent volume

1. Read the solute amount

The beaker currently holds 11 units of solute.

2. Read the solvent volume

The same solute is spread through 1 units of solvent.

3. Use both to read the concentration

That gives a concentration of about 11, with roughly 40 visible particles in the beaker.

Beaker concentration

c \approx 11

With less liquid in the beaker, the same solute occupies a tighter space and the concentration rises.

Quick test

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Crowded beaker

Open a concentrated case and notice many solute particles packed into a small solvent volume.

Dilute without losing solute

Open the same solute amount in more liquid and compare how the particles spread out as concentration falls.

More solute at fixed volume

Open the numerator-change case so adding solute does not get confused with dilution.

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Solutions and pH

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