lecture 12.1- interpreting balanced equations
DESCRIPTION
Section 12.1 Lecture for Honors & Prep ChemistryTRANSCRIPT
Balance the following chemical equations by adding coefficients in front of the compounds.
Example- 2H2 + O2 2H2O
1. MgCl2 + AgNO3 AgCl + Mg(NO3)2
2. C3H8 + O2 CO2 + H2O
3. Al + AgNO3 Ag + Al(NO3)3
4. C12H22O11 C + H2O
An unbalanced equation is mathematically useless!
Bellwork
Balance the following chemical equations by adding coefficients in front of the compounds.
Example- 2H2 + O2 2H2O
1. MgCl2 + AgNO3 AgCl + Mg(NO3)2
2. C3H8 + O2 CO2 + H2O
3. Al + AgNO3 Ag + Al(NO3)3
4. C12H22O11 C + H2O
An unbalanced equation is mathematically useless!
Bellwork
NEVER change subscripts
A balanced chemical equation provides the same kind of quantitative information that a recipe does.
Mass and atoms are conserved in every chemical reaction.
Mass of reactants = mass of products
Number and type of atoms in reactants = number & type atoms in products
A balanced chemical equation can be interpreted in terms of different quantities.
•numbers of atoms
•Molecules
•Moles
•Mass
•volume.
N2(g) + 3H2(g) 2NH3(g)
2 N + 6 H = 2 N + 6HAtoms are conserved!!
N2(g) + 3H2(g) 2NH3(g)
Coefficients tell us the RATIO of molecules
N2(g) + 3H2(g) 2NH3(g)
Coefficients tell us the RATIO of molecules
one N2 + three H2 two NH3
molecule molecules molecules
N2(g) + 3H2(g) 2NH3(g)
Coefficients tell us the RATIO of moles
N2(g) + 3H2(g) 2NH3(g)
one mole + three moles two moles N2 H2
NH3
Coefficients tell us the RATIO of moles
N2(g) + 3H2(g) 2NH3(g)
Find the molar mass of each compound & multiply by the coefficient
N2(g) + 3H2(g) 2NH3(g)
28g + 3 x 2g 2 x 17g
N2(g) + 3H2(g) 2NH3(g)
Find the molar mass of each compound & multiply by the coefficient
28g + 3 x 2g 2 x 17g Why do you multiply the molar mass by three?
N2(g) + 3H2(g) 2NH3(g)
Find the molar mass of each compound & multiply by the coefficient
28g + 3 x 2g 2 x 17g 28g + 6g 34g
N2(g) + 3H2(g) 2NH3(g)
Find the molar mass of each compound & multiply by the coefficient
34g = 34gMass is conserved!
28g + 3 x 2g 2 x 17g 28g + 6g 34g
N2(g) + 3H2(g) 2NH3(g)
Find the molar mass of each compound & multiply by the coefficient
N2(g) + 3H2(g) 2NH3(g) At STP, one mole of gas occupies 22.4 liters.
22.4L N2 + 322.4L H2 222.4L
NH3
N2(g) + 3H2(g) 2NH3(g) At STP, one mole of gas occupies 22.4 liters.
22.4L 22.4L 22.4L 22.4L 22.4L 22.4L
N2(g) + 3H2(g) 2NH3(g) At STP, one mole of gas occupies 22.4 liters.
22.4L N2 + 322.4L H2 222.4L
NH3
22.4L 22.4L 22.4L 22.4L 22.4L 22.4L
N2(g) + 3H2(g) 2NH3(g) At STP, one mole of gas occupies 22.4 liters.
22.4L N2 + 67.2L H2 44.8L
NH3
22.4L N2 + 322.4L H2 222.4L
NH3
Chemists use stoichiometry and mole ratios to calculate how much reactant is needed or how much product will be formed.
The first step in stoichiometry is to get a balanced equation.
The first step in stoichiometry is to get a balanced equation.
H2 + O2 H2O unbalanced (why?)
The first step in stoichiometry is to get a balanced equation.
H2 + O2 H2O unbalanced (why?)
2H2 + O2 2H2O balanced
The first step in stoichiometry is to get a balanced equation.
H2 + O2 H2O unbalanced (why?)
2H2 + O2 2H2O balanced
simple stoichiometry- How many moles of hydrogen gas are needed to make two moles of water?
The first step in stoichiometry is to get a balanced equation.
H2 + O2 H2O unbalanced (why?)
2H2 + O2 2H2O balanced
simple stoichiometry- How many moles of hydrogen gas are needed to make two moles of water?
2 moles of H2(g)
2H2 + O2 2H2O
How many moles of O2 are needed to completely react with 4 moles of H2?
2H2 + O2 2H2O
How many moles of O2 are needed to completely react with 4 moles of H2?
2 moles of O2(g)
Conceptual Problem 12.1
Conceptual Problem 12.1
Conceptual Problem 12.1
Production of iron metal from iron ore–
Fe2O3•H2O(s) + 3CO(g) 2Fe(s) + 3CO2(g) + H2O(g)
In this equation, the volume of gas at STP that reacts and the volume of gas at STP produced will be
a. 3 L and 4 L.
b. 67.2 L and 89.6 L.
c. 67.2 L and 67.2 L
d. 3 L and 3 L
What is conserved in the following reaction?
H2(g) + Cl2(g) 2HCl(g)
a. only mass
b. only mass and number of moles
c. only mass, number of moles, and number of molecules
d. mass, number of moles, number of molecules, and volume