Reacting Mass Calculations

Lab Brief #5

🎯 Your mission

Run the experiment. Find out what really happens.

⚡ The twist

Nature loves to surprise the careful watcher.

What you'll learn

A balanced equation gives the mole ratio between substances — this is what stoichiometry means. Convert the known mass to moles, apply the ratio, then convert back to mass. It is exactly how a manufacturer works out how much raw material a batch of product needs.

Key words

mole ratio
The ratio of amounts of substances given by a balanced equation's coefficients.
theoretical yield
The mass of product predicted by a reacting mass calculation.

Make a hypothesis first

Before you start: write down what you think will happen, and why.

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

crucible and lid
pipeclay triangle
tripod
Bunsen burner
balance
calcium carbonate
tongs

Get ready

⚠️ Safety first

The crucible stays hot long after the flame is out — move it only with tongs onto a heatproof mat.
Tie back hair, wear goggles, and have an adult supervise the Bunsen.

Step 1 of 4 · Read

Think about what you just learned: say what "mole ratio" and "theoretical yield" mean in your own words before you start.

Step 2 of 4 · Do

Calculate the mass of calcium oxide produced by decomposing 25 g of calcium carbonate. Then heat a weighed sample of calcium carbonate in a crucible, reweigh, and compare the real mass loss with your prediction.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

The mole ratio between substances comes from the:

How sure are you?😐 maybe

Question 2 of 2

In a reacting mass calculation, the first step is to convert the known mass to:

How sure are you?😐 maybe

Mind = blown

🔬 The more you look, the more nature shows you.

Nice work!

You got 0 of 2 right.

Next: Limiting Reactants and Percentage Yield All lessons

🎯

Next Smart Experiment

We'll pick an experiment that matches exactly how you're thinking right now.

✨ More to explore

🌍 Where you see this in real life: This shows up in your everyday life more than you'd think.

🏆 Stretch challenge (try it this week): Try one experiment in real life this week — even a tiny one.

👨‍👩‍👧 For the dinner table: “What's the most surprising thing you learned today?”

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Reacting Mass Calculations

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