Menu

Mass to Mass

Part of the Stoichiometry section of Coddy's Chemistry journey. Lesson 20 of 41.

Equations count moles, balances weigh grams. Go through moles in three steps: mass of A to moles of A, the mole ratio to moles of B, then moles of B to mass of B.

2Mg + O₂ → 2MgO from $4.8\ \mathrm{g}$ of Mg: $n_{Mg} = \frac{4.8}{24} = 0.2\ \mathrm{mol}$ , so $0.2\ \mathrm{mol}$ of MgO.

MgO is $40\ \mathrm{g/mol}$ : $m = 0.2 \times 40 = 8.0\ \mathrm{g}$ .

Two balances: 4.8 g of magnesium and 8.0 g of magnesium oxide

4.8 g Mg, 8.0 g MgO

Challenge

Lime, CaO, is made by heating limestone: CaCO₃ → CaO + CO₂. What mass of CaO ( $56\ \mathrm{g/mol}$ ) does $25\ \mathrm{g}$ of CaCO₃ ( $100\ \mathrm{g/mol}$ ) make?

Try it yourself

Physics diagram: balance

Solve for $m_{CaO}$

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Stoichiometry

1The Mole

Counting Particles: the Mole Avogadro's Number Molar Mass Mass, Moles and Particles Moles in a Formula Recap - Mole Bridge

4Equations and Mole Ratios

Balancing Equations Reading an Equation in MolesMass to MassGas Volumes in Reactions Reactions in Solution Precipitation Recap - Rocket Fuel

2Gases

Molar Volume of a Gas Avogadro's Law Pressure, Volume, Temperature The Ideal Gas Law Recap - Weather Balloon

5Limiting Reactant

The Limiting Reactant What Is Left Over Industrial Scale Recap - Aluminum Plant

3Solutions

Molar Concentration Preparing a Solution Ions in Solution Ion Concentrations Dilution Recap - Lab Prep

6Practice Problems

Recap - Fertilizer Plant Recap - Acid for the Plant Recap - Gases for Ammonia Recap - Ions in the Sample Recap - The Full Plant Recap - Bromide in Brine Recap - Chlorine for Bromine Recap - Magnesium Bromide Recap - Silver Bromide Test Recap - Balloon at Launch Recap - Balloon High Up Recap - Before It Bursts Recap - Hydrogen from Water