Concentration & Titration
How concentrated is a solution, and how do we measure it? Learn concentration in g/dm3 and mol/dm3, the cm3-to-dm3-to-moles chain, and the titration technique that finds an unknown concentration - with the calculations to match.
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How concentrated is it? 🧪
A **concentrated** squash has lots of solute in the water; a **dilute** one has little. Chemists need to say exactly how much - and to measure it accurately. This module covers **concentration** (in g/dm3 and mol/dm3), the calculations that link mass, moles and volume, and **titration** - the technique for finding an unknown concentration.
The words you need 🔑
Four terms underpin the topic:
Match each piece of apparatus to its job 🔗
- Burette
- Pipette
- Conical flask
- Indicator
- Delivers a measured, variable volume of acid
- Measures a fixed volume of alkali accurately
- Holds the solution being titrated
- Shows the endpoint by changing colour
Units of concentration ⚖️
Which of these is a unit of concentration?
- mol/dm3
- g (grams)
- cm3
- degrees Celsius
The concentration formula 📏
Concentration links the amount of solute to the volume of solution: - **concentration (g/dm3) = mass (g) / volume (dm3)** - **concentration (mol/dm3) = moles / volume (dm3)** Watch the units: volume must be in **dm3**, and **1 dm3 = 1000 cm3**, so divide a cm3 volume by 1000 first.
Convert the volume 📐
An interactive activity.
True of titration ✅
Select the TWO statements that are true about carrying out a titration.
- An indicator shows when the reaction is complete, at the endpoint
- A burette measures the variable volume of acid added
- Titration is used to measure temperature
- You add all the acid at once, as fast as possible
Concentration in g/dm3 🧮
An interactive activity.
Two ways to give concentration ⚗️
The same solution can be described in grams or in moles per dm3.
Find the moles 💧
An interactive activity.
Put it together 🧱
A _____ measures a fixed volume of alkali into a flask. Acid is added from a _____ until an _____ shows the _____. Concentration in mol/dm3 equals moles divided by the _____ in dm3.
The titration method 🪜
An interactive activity.
Run the titration 🎯
An interactive activity.
The grade-9 chain 🌟
Top answers **chain the calculation cleanly**: convert the volume (cm3 to dm3 by dividing by 1000), find the moles if needed (mass / Mr), then divide by the volume for the concentration. Link the **technique** to the **numbers**: the pipette fixes the volume, the burette measures the acid added, the indicator marks the endpoint, and concordant repeats make the result reliable. Method plus calculation, with the right units - top band.