CHAPTER 10 Chemical Reactions 10.1 Chemical Equations

The alphabet of chemistry More than 200,000 words in the English language Trillions of substances that make up the universe

The language of chemistry Element symbols H, O, Na, Fe Alphabet of chemistry

The language of chemistry Element symbols H, O, Na, Fe Compound formulas H2O, CO2, NaCl Alphabet of chemistry Words

The language of chemistry Element symbols H, O, Na, Fe Compound formulas H2O, CO2, NaCl Chemical equations 2H2 + O2 2H2O Alphabet of chemistry Words Sentences

Chemical reactions tell a story Chemical equations 2H2 + O2 2H2O Sentences of chemistry Reactants Products Chemical reactions tell a story chemical equation: an expression that describes the changes that happen in a chemical reaction.

Consider one reaction that takes place in a fire:

Consider one reaction that takes place in a fire: Carbon (from wood) reacts with oxygen (from the atmosphere) to produce carbon dioxide gas

Consider one reaction that takes place in a fire: carbon + oxygen Carbon (from wood) reacts with oxygen (from the atmosphere) to produce carbon dioxide gas

Consider one reaction that takes place in a fire: carbon + oxygen carbon dioxide Carbon (from wood) reacts with oxygen (from the atmosphere) to produce carbon dioxide gas

Consider one reaction that takes place in a fire: carbon + oxygen carbon dioxide C + O2 CO2

Consider one reaction that takes place in a fire: carbon + oxygen carbon dioxide C + O2 CO2 Reactants Products

Consider one reaction that takes place in a fire: carbon + oxygen carbon dioxide separates the reactants arrow points toward the products C + O2 CO2 Reactants Products

Consider one reaction that takes place in a fire: C + O2 CO2 1 mole 1 mole 1 mole

Consider one reaction that takes place in a fire: C + O2 CO2 1 mole x 12 g/mole 1 mole x 32 g/mole 1 mole x 44 g/mole

Consider one reaction that takes place in a fire: C + O2 CO2 1 mole x 12 g/mole = 12 g 1 mole x 32 g/mole = 32 g 1 mole x 44 g/mole = 44 g

Consider one reaction that takes place in a fire: C + O2 CO2 1 mole x 12 g/mole = 12 g 1 mole x 32 g/mole = 32 g 1 mole x 44 g/mole = 44 g Total mass of reactants = 44 g Total mass of products = 44 g

Total mass of reactants 1 mole x 12 g/mole = 12 g 1 mole x 32 g/mole = 32 g 1 mole x 44 g/mole = 44 g C + O2 CO2 Total mass of reactants = 44 g Total mass of products = 44 g

Reaction that fuels the space shuttle: Hydrogen burns with oxygen to produce water The “white smoke” is actually water vapor

Reaction that fuels the space shuttle: Hydrogen burns with oxygen to produce water hydrogen + oxygen water

Reaction that fuels the space shuttle: hydrogen H2 + oxygen O2 water H2O

Reaction that fuels the space shuttle: hydrogen H2 + oxygen O2 water H2O

Reaction that fuels the space shuttle: hydrogen H2 + oxygen O2 water H2O 2 hydrogen atoms 2 oxygen atoms 2 hydrogen atoms 1 oxygen atom

Reaction that fuels the space shuttle: hydrogen H2 + oxygen O2 water H2O 2 hydrogen atoms 2 oxygen atoms 2 hydrogen atoms 1 oxygen atom

This chemical equation is not balanced: it violates the law of conservation of mass Hydrogen H2 + Oxygen O2 Water H2O 2 hydrogen atoms 2 oxygen atoms 2 hydrogen atoms 1 oxygen atom

2H2 From Chapter 4.2 Subscript tells how many atoms in 1 molecule Hydrogen gas

2H2 From Chapter 4.2 Coefficient tells how many molecules are involved Hydrogen gas

2H2 From Chapter 4.2 Coefficient tells how many molecules are involved Subscript tells how many atoms in 1 molecule Hydrogen gas When balancing a chemical equation, only coefficients can be changed Subscripts remain the same

2H2 O2 3H2O Coefficients 2 hydrogen molecules 1 oxygen molecule Atoms 2 hydrogen molecules 1 oxygen molecule 3 water molecules 2H2 O2 3H2O

2H2 O2 3H2O Coefficients 2 hydrogen molecules 1 oxygen molecule Atoms 2 hydrogen molecules 1 oxygen molecule 3 water molecules 2H2 O2 3H2O

2H2 O2 3H2O Coefficients 2 hydrogen molecules 1 oxygen molecule Atoms 2 hydrogen molecules 1 oxygen molecule 3 water molecules 2H2 O2 3H2O

2H2 + O2 2H2O The balanced chemical equation: Reactants Products Molecules Atoms

The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction.

The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction. Asked: The coefficients needed to balance the chemical equation Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2 Relationships: The same number of each type of atom must appear on each side.

The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction. Asked: The coefficients needed to balance the chemical equation Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2 Relationships: The same number of each type of atom must appear on each side. Solve: All atoms involved in the reaction are unbalanced. There are 6 C atoms, 12 H atoms, and 6 O atoms in the reactants. There are 3 C atoms, 6 H atoms, and 3 O atoms in the products. From this accounting, we notice that the number of atoms in the products is half the number of atoms in the reactants.

The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction. Asked: The coefficients needed to balance the chemical equation Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2 Relationships: The same number of each type of atom must appear on each side. Solve: All atoms involved in the reaction are unbalanced. There are 6 C atoms, 12 H atoms, and 6 O atoms in the reactants. There are 3 C atoms, 6 H atoms, and 3 O atoms in the products. From this accounting, we notice that the number of atoms in the products is half the number of atoms in the reactants. By multiplying the products by a factor of 2 we obtain a balanced chemical equation of the reaction.

The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction. Asked: The coefficients needed to balance the chemical equation Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2 Relationships: The same number of each type of atom must appear on each side. Solve: All atoms involved in the reaction are unbalanced. There are 6 C atoms, 12 H atoms, and 6 O atoms in the reactants. There are 3 C atoms, 6 H atoms, and 3 O atoms in the products. From this accounting, we notice that the number of atoms in the products is half the number of atoms in the reactants. By multiplying the products by a factor of 2 we obtain a balanced chemical equation of the reaction. Answer: The balanced chemical equation is C6H12O6 → 2C2H6O + 2CO2.

2H2 Coefficient tells how many molecules are involved When balancing a chemical equation, only coefficients can be changed Subscripts remain the same 2H2 Subscript tells how many atoms in 1 molecule