Lesson 13 The Mole
The Law of Conservation of Mass
The total amount of reactants must equal the total amount of products.
You have already applied the law of conservation of mass when you balanced chemical reaction equations. The total number of atoms of each element needed to be carefully inspected and coefficients were added to ensure that the number of atoms of each
element on the reactant side of the equation equaled the number of atoms of each element on the product side.
Not only can you use the number of atoms to explain the law of conservation of mass, but you can also use the number of moles or even the mass. Using the combustion of methane as our example, this chart compares the amount of reactants to the amount of products.
Not only can you use the number of atoms to explain the law of conservation of mass, but you can also use the number of moles or even the mass. Using the combustion of methane as our example, this chart compares the amount of reactants to the amount of products.
| Balanced Chemical Equation |
CH4(g) + |
2O2(g) | → | CO2(g) + |
2H2O(g) |
| Number of Particles | 1 molecule of CH4 | 2 molecules of O2 |
→ | 1 molecule of CO2 | 2 molecules of H2O |
| Amount (mol) | 1 mol CH4 | 2 mol O2 | → | 1 mol CO2 | 2 mol H2O |
| Mass (g) |
16.05 g |
64.00 g |
→ | 44.01 g |
36.04 g |
| Total Mass (g) |
80.05 g |
→ | 80.05 g |
||
Read This
Please read page 111 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on applying the law of conservation of mass
to the mole concept. Remember, if you have any questions or you do not understand something, ask your teacher! Practice Questions
Complete the following practice question to check your understanding of the concept you just learned. Make sure you write a complete answer to the practice
question in your notes. After you have checked your answer, make corrections to your response (where necessary) to study from.- Predict the mass of nitrogen monoxide gas that should be produced when 28.02 g of nitrogen gas reacts with 32.0 g of oxygen gas.
According to the law of conservation of mass, the amount of nitrogen monoxide produced should be 60.02 g.