1) Write the reaction for Calcium and nitrogen reacting

3) What element on the periodic table is the largest?

3)Name thesea) H2S(aq) b) HNO3 (aq)

Stoichiometry: mathematical relationships in formulas and equations

Conversion factor: a fraction equal to “one” that is used the change from one unit to another (numerator = denominator)

Dimensional analysis: a problem solving method where the desired quantity is obtained by using conversion factors to cancel out unwanted units (the box method!)

a. $25 to nickels

b. 2.5 miles to inches

c. 180 days to minutes

d. 125 cm to km

e. 15 m/s to km/hr

Formula Mass: sum of the average atomic masses of all of the atoms in the formula of any molecule, formula unit or ion

Use periodic table mass times number of atoms of each

NaCl:

Al2(SO4)3:

NiSO3*6H2O:

Definition: percent by mass of each element in a compound

Formula:

100*compoundofMass

elementofMass

Find the % of Sodium and Chlorine in NaCl

Find the % composition of each element in: Al2(SO4)3

Find the % of H2O in NiSO3*6H2O

1) Find the formula mass forCu(NO3)2

2) Find the % of Cu, N and O in Cu(NO3)2

Empirical formula: simplest formula, shows smallest whole number ratio of elements in a compound

Molecular formula: the actual formula for a molecular compound, often it is a multiple of the empirical formula ex: C6H6

1) If you are given % you may change the percent to grams

2) Convert grams to moles by dividing by the molar mass of the element

3) Divide by the smallest answer4) If the ratio is not a whole number-multiply

each value by the same number to make the value a whole number

**these values are subscripts**

What is the empirical formula of a compound that is 66% calcium and 34.0% phosphorus?

*For this problem, assume you have 100 grams of the compound. This means your percentages are now also the number of grams.*

1) Find the formula mass of N2H3.

2) What is the percent composition of each of the elements in N2H3?

3) How many valence electrons does Nitrogen have?

A compound is found to contain 50.05 % sulfur and 49.95 % oxygen by weight. What is the empirical formula for this compound

A compound is found to contain 64.80 % carbon, 13.62 % hydrogen, and 21.58 % oxygen by weight. What is the empirical formula for this compound

(Empirical Mass)n = Molecular Mass

n=integer

Find the mass of the empirical formula.

Divide the molecular mass by the mass of the empirical formula to get the “multiplying factor.”

Multiply EACH of the subscripts in the empirical formula by this factor to get the molecular formula.

A compound has an empirical formula of: CH2O. Its molecular mass is 180 grams. What is the molecular formula?

Chemical Mole: SI base unit used to measure the amount of a substance.

The # of particles (carbon atoms) in exactly 12 grams of Carbon-12.

Avogardo’s number: 6.02 x 1023

602,000,000,000,000,000,000,000

1 mole of any substances equals 6.02 x 1023

think about it: 1 dozen doughnuts = 12 doughnuts 1 mole of doughnuts = 6.02 x 1023 doughnuts

Molar Mass: (g/mol) the mass in grams of one mole of a substance, equal to the formula mass at standard temperature and pressure

Molar Volume: the volume of one mole of gas occupies at standard temperature and pressure (22.4 L/mol)

Formula mass(in grams

from Periodic Table)

MassVolume @ STP

# particles

22.4 L

Gases only

6.02 * 1023

Units: molecules, atoms, ions, or formula units

1 Mole

1) How many grams are in 2.52 moles of NH3?

2) How many moles are in 8.75 grams of LiBr?

How big is a mole?

Grams-Particles

Particles-mole

Mole-grams

a. 38 grams Aluminum to moles

b. 2.5 moles Calcium oxide to grams

c. 3.1 moles Neon to atoms

d. 1.2*1024 molecules water to moles

e. 5.0L of carbon dioxide to moles (@ STP)

f. 1.5 moles NH3 gas to liters (@STP)

g. 54.0 grams water to molecules

1) Empirical Formula2) Molecular Formula3) % Composition4) Formula Mass5) Mole Conversions with the mole diagram*One and multiple step problems

*Note Test has been moved to Next Tuesday!

Stoichiometry requires a balanced chemical equation. A mole to mole ratio is used to convert from one substance to another in a balanced reaction. This ratio comes from the coefficients in your reaction.

Using the following reaction, write ALL of the mole ratios:

2H2(g) + O2(g) 2H2O(g)

Balance and write ALL of the mole ratios for the following reaction:

Al(NO3)3 + NaOHAl(OH)3 + NaNO3

1) 2KClO3 2KCl + 3 O2

Write 3 mole ratios for the above equation

2) What is the molecular formula for a compound with a mass of 80.25 if the empirical formula is CH4

Empirical Formulas Mole Ratios Mole-Mole Mole-Grams Mole Diagram ( I will NOT be giving you the

diagram tomorrow ) Molecular Formula Formula Mass % composition

Write and balance your reaction. Convert grams of the given to moles of the

given. Convert moles of given to moles of unknown Convert moles of unknown to grams of

unknown.

Laughing gas, N2O, is produced from the decomposition of ammonium nitrate. Water is your other product. How many grams of ammonium nitrate are

required to produce 33.0 grams of laughing gas?

Mole-Mass

2H2 + O2 2 H2O

How many grams of water are produced when 0.98 grams of H2 react with oxygen?

2KClO3 2 KCl + 3O2

How many moles of oxygen form when 80.2 grams of KClO3 decompose?

Mass to mass (the longest set up YAY)

2LiCl + Br2 2LiBr + Cl2

How many grams of bromine are produced when 10.5 grams of lithium bromide are formed?

Pb(SO4)2 + 4LiNO3 Pb(NO3)4 + 2Li2SO4

How many grams of lithium nitrate will be needed to make 250 grams of lithium sulfate assuming that you have an adequate amount of lead (IV) sulfate to do the reaction?

Convert from mass of one to the volume of another. Hydrogen gas is produced by reacting zinc metal

with hydrochloric acid. How many liters of hydrogen gas can be produced at STP from 6.5 grams of zinc and an excess of acid?

Write and balance reaction

Convert given grams to moles

Convert given moles to unknown moles (mole ratio)

Convert unknown moles to unknown volume (molar volume)

How many grams of zinc are needed to produce 100. L of hydrogen?

The complete combustion of methane produces carbon dioxide and water. How many liters of oxygen would be needed to produce 25 liters of carbon dioxide at STP?

Write and balance reaction

Convert volume of given to volume of unknown, using the volume ratio.

How many liters of methane gas are needed?

Mole Ratios are used when you are “switching” between two different substances

Mole diagrams are used when you are using the same substance but changing between different quanitites (L-g, L-molecules, etc)

Theoretical yield: “true yield” the calculated amount of product that can be formed in a chemical reactions

Actual yield: the actual amount of product obtained in an experiment

Equation:

100% ltheoretica

actualyield

100*%ltheoretica

actualyield

The actual yield has to be given to you or you have to measure it in lab.

The theoretical yield may or may not be given to you directly. You can calculate it using a stoichiometry problem.

The actual yield of a compound in an experiment was 36.8 grams. The theoretical yield for this compound was 38.8 grams. What is the percent yield?

2H2 + O2 2H2O If you start with 5.00g of hydrogen gas at

STP, how many liters of water vapor will be formed?

Find the % yield if 17.5 L of H2O were produced