Balancing Equations

Balancing Equations Chapter 13.2

Standards: • GLE 0807.9.4 • Distinguish among elements, compounds, and mixtures. • GLE 0807.9.9 • Explain the law of conservation of mass • GLE 0807.9.8 • Interpret the events represented by a chemical equation

Key concepts: • Interpret and write simple chemical formulas • Identify the reactants and products of a chemical reaction.

Key Vocabulary: • Reactant • Product • Law of conservation of mass

What do you already know? Now imagine having to write out names! • Where do you find reactants? • Where do you find products? • Why do we use symbols instead of writing out everything? • What does conservation mean?

Let’s talk compound vs. element: • Is it a compound or element? He

Let’s talk compound vs. element: • Is it a compound or element? • How many atoms? CO2

Let’s talk compound vs. element: • Is it a compound or element? • How many atoms? NaClO

Chemical Reaction: Think of this a piece of sheet music... Cheat sheet time! Reactants point to products R  P • Chemical equation uses symbols and formulas to describe a chemical reaction. • Parts: • Reactants—starting materials • Products—what you make • Yield—this is the arrow sign • This usually means that energy is going in or out

Balancing Equations: How many atoms? -H20 -C6H1206 -CH4 R  P • Conservation means the before is equal to the after…meaning whatever we do to the reactants, we must do to the products. • All atoms must be equal • Law of conservation of mass states that the mass is neither created nor destroyed in a chemical change. • Reactants = Products

Balancing the Parts: How many atoms? -H20 -C6H1206 -CH4 • Important parts: • Coefficient: the number that is place in the front of a symbol • This is what WE will use to balance the equation • Subscripts • Number written below and to the right of the symbol

Balancing the Parts: Remember to keep track of the atoms! Practice times • How to balance: • Determine the number of atoms for each element • Pick an element that is not equal on both sides (start with metals) • Add a coefficient in front the formula with that element and adjust your counts • Continue to add coefficients to get the same number of atoms of each side

Balancing Equations • Hydrogen + oxygen water • H2 + O2 H2O • Hydrogen and oxygen are diatomicelements. • Their subscripts cannot be changed. • The subscripts on water cannotbe changed.

Balancing Equation • H2 + O2 H2O • Count the atoms on each side. • Reactant side: 2 atoms H and 2 atoms O • Product side: 2 atoms H and 1 atom O

Balancing Equations H2 + O2 H2O If the subscripts cannot be altered, how can the atoms be made equal? Adjust the number of molecules by changing the coefficients.

Balancing Equations • H2 + O22H2O • Reactants: 2 atoms of H and 2 atoms of O • Products: 4 atoms of H and 2 atoms of O • H is no longer balanced!

Balancing Equations • 2H2 + O22H2O • Reactantside: 4 atoms of H and 2 atoms of O • Productside: 4 atoms of H and 2 atoms of O • It’s Balanced!

Balancing Equations • N2 + H2 NH3 • Nitrogen + hydrogen ammonia • Count atoms. • Reactants: 2 atoms N and 2 atoms H • Products: 1 atom N and 3 atoms of NH3

Balancing Equations • Nothing is balanced. • Balance the nitrogen first by placing a coefficient of 2 in front of the NH3. N2 + H22NH3

Balancing Equations • Hydrogen is not balanced. • Place a 3 in front of H2. • Reactant side: 2 atoms N, 6 atoms H • Product side: 2 atoms N, 6 atoms H N2 + 3H22NH3

We need practice! • On the back of your notes, let’s practice. • Do not write on the hand-outs. I will take these up when you leave. • Balancing Act

Pearls of Wisdom: • How do you balance equations? • What are some important steps?

Homework: • Finish your worksheet.

Balancing Equations