Chapter 6
Be able to give evidence for chemical reactions
Some of the evidence is that the color changes, a solid forms, bubbles form, and heat and/or a flame is produced, or heat is absorbed
Understand the parts of the chemical equation
Represent a chemical reaction by writing a chemical equation in which the chemicals present before the reaction (the reactants) are shown to the left of the arrow and the chemicals formed by the reaction (the products) are shown to the right of an arrow.
Be able to balance chemical equations
All atoms are present in the reactants must be accounted for among the products. In other words, there must be the same number of each type of atom on the product side as on the reactant side of the arrow.
Some of the evidence is that the color changes, a solid forms, bubbles form, and heat and/or a flame is produced, or heat is absorbed
Understand the parts of the chemical equation
Represent a chemical reaction by writing a chemical equation in which the chemicals present before the reaction (the reactants) are shown to the left of the arrow and the chemicals formed by the reaction (the products) are shown to the right of an arrow.
Be able to balance chemical equations
All atoms are present in the reactants must be accounted for among the products. In other words, there must be the same number of each type of atom on the product side as on the reactant side of the arrow.
Calculations
Example of Balancing a Chemical Equation
CH4 + ? O2 → ? CO2 + ? H2O
Identify the elements in the equation: C, H, O
Identify the net charge: no net charge, which makes this one easy!
CH4 + ? O2 → ? CO2 + ? H2O
Identify the elements in the equation: C, H, O
Identify the net charge: no net charge, which makes this one easy!
- H is found in CH4 and H2O, so it's a good starting element.
- You have 4 H in CH4 yet only 2 H in H2O, so you need to double the coeffient of H2O to balance H. 1 CH4 + ? O2 → ? CO2 + 2 H2O
- Looking at carbon, you can see that CH4 and CO2 must have the same coefficient. 1 CH4 + ? O2 → 1 CO2 + 2 H2O
- Finally, determine the O coefficient. You can see you need to double the O2 coefficient in order to get 4 O seen on the product side of the reaction.1 CH4 + 2 O2 → 1 CO2 + 2 H2O
- Check your work. It's standard to drop a coefficient of 1, so the final balanced equation would be written: CH4 + 2 O2 → CO2 + 2 H2O
Video
This video shows us how to balance equations.