Balancing Chemical Equations

What are the reactants and products of the given chemical reaction?

• reactants: hydrogen gas and chlorine gas

  product: hydrochloric acid

• reactants: hydrochloric acid 

  product: hydrogen gas and chlorine gas

• reactants: hydrochloric acid and chlorine gas

  product: hydrogen gas

• It cannot be determined

Make sure to take note of what it means for a chemical equation to be balanced!

Do you think the given equation is balanced?

• Yes

• No

How many atoms of each element are on the left side of the arrow? (the reactants?)

• 2 hydrogen atoms and 1 chlorine atom

• 1 hydrogen atom and 2 chlorine atoms

• 2 hydrogen atoms and 2 chlorine atoms

• 1 hydrogen atom and 1 chlorine atom

How many HCl is needed to balance this equation?

• 1HCl

• H₂Cl₂

• 2HCl

• 3HCl

This chemical equation is...

• unbalanced.

• balanced.

How many atoms of each element are on the right side of the arrow (the products)?

• 1 hydrogen atom and 1 oxygen atom

• 2 hydrogen atoms and 2 oxygen atoms

• 1 hydrogen atom and 2 oxygen atoms

• 2 hydrogen atoms and 1 oxygen atom

How many H₂ molecules do we need in the reactants to balance the equation?

• 2 H₂ molecules for 4 H atoms total

• 4 H₂ molecules for 4 H atoms total

Why do you think this is incorrect?

What can we change to balance a chemical equation?

• The coefficients: numbers in front of the molecules 

  2 H₂

• Both coefficients and subscripts 

• The subscripts: the little numbers next to the molecules 

  2 H₂