Aim: How to determine the mass of a mole of an element and of a compound  DO Now: 1.With a partner, complete the worksheet from Friday. 2.If you have finished define or explain the following: 1.Converting from number of particles to number of moles 2.Converting from number of moles to number of particles 3.Based on your reading define the term “molar mass.”  DO Now: 1.With a partner, complete the worksheet from Friday. 2.If you have finished define or explain the following: 1.Converting from number of particles to number of moles 2.Converting from number of moles to number of particles 3.Based on your reading define the term “molar mass.”

Molar Mass  The mass of a mole (1 mole) of any substance is called its molar mass.  Molar mass is the atomic mass of an element expressed in grams  Ex: The molar mass for carbon is 12.0 g. In other words, 1 moles of carbon has a mass of 12.0 g.  The mass of a mole (1 mole) of any substance is called its molar mass.  Molar mass is the atomic mass of an element expressed in grams  Ex: The molar mass for carbon is 12.0 g. In other words, 1 moles of carbon has a mass of 12.0 g.

Molar Mass of Compound  To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound.

CALCULATION OF MOLAR MASS X = X = X = LISTELEMENTSHERE CALCULATE THE MOLAR MASS OF K 2 Cr 2 O 7

CALCULATION OF MOLAR MASS KX = CrX = OX = LISTELEMENTSHERE CALCULATE THE MOLAR MASS OF K 2 Cr 2 O 7

CALCULATION OF MOLAR MASS K2X = Cr2X = O7X = LISTELEMENTSHERE LIST SUBSCRIPTS MULTIPLY By atomic mass K 2 Cr 2 O 7

CALCULATION OF MOLAR MASS K2X g/MOL = Cr2X g/MOL = O7X g/MOL = LISTELEMENTSHERE LIST SUBSCRIPTS MULTIPLY By atomic mass INSERT ATOMIC MASS FROM PERIODIC TABLE

CALCULATION OF MOLAR MASS K2X g/MOL = g Cr2X g/MOL = g O7X g/MOL = g LISTELEMENTSHERE LIST SUBSCRIPTS MULTIPLY By atomic mass INSERT ATOMIC MASS FROM PERIODIC TABLE Add SUBTOTALS g/mol

Solve 1.What is the mass of 1 mole of H 2 SO 4 ? 2.What is the molar mass of NO 2 ? 3.What is the mass of 2 moles of NO 2? 1.What is the mass of 1 mole of H 2 SO 4 ? 2.What is the molar mass of NO 2 ? 3.What is the mass of 2 moles of NO 2?

Aim: How to convert from mass to moles and vice versa  Do Now: 1.Find the molar mass of the following: 1.Oxygen 2.Hydrogen fluoride 3.Calcium chloride 4.Ammonium nitrate 5.Sodium phosphate  Do Now: 1.Find the molar mass of the following: 1.Oxygen 2.Hydrogen fluoride 3.Calcium chloride 4.Ammonium nitrate 5.Sodium phosphate

Review: moles  particles

Converting mass  mass

The Mole- Mass Relationship  Use the molar mass of an element or a compound to convert between mass of a substance and the moles of a substance.

Convert from Moles to Mass Conversion Factor

 To convert from moles to mass you multiply the number of moles given by the molar mass. Remember, molar mass is the mass of 1 mole of that substance. ( given moles times molar mass)

Example

Practice  What is the mass of 3 moles of manganese?

Practice  What is the mass of 0.5 mol of hydrogen gas (H 2 )?

Convert mass to number of moles Conversion Factor

 To convert from mass to number of moles you multiply the mass by the inverse of the molar mass. (given mass divided by molar mass)

Example  How many moles is 108 grams of H 2 O? 1.List the known and unknown. KnownUnknown - Molar mas of H 2 O =# moles in 108 grams of H 2 O (2 x 1.0g/mol H ) + 16 g/mol O = 18.0 g/mol H 2 O -Given mass 108 g  How many moles is 108 grams of H 2 O? 1.List the known and unknown. KnownUnknown - Molar mas of H 2 O =# moles in 108 grams of H 2 O (2 x 1.0g/mol H ) + 16 g/mol O = 18.0 g/mol H 2 O -Given mass 108 g

Cont.

Practice  How many moles of NaOH are present in 90.0 g of NaOH?  To solve this, divide 90.0 g by 40 g/mol or multiply 90.0 g by the reciprocal of 40 g/mol (1 mol/40 g) to get the unit (g) to cancel out.  90g NaOH ⋅ 1 mol40g=2.25 mol NaOH  The final answer is 2.25 moles in 90g of NaOH.  How many moles of NaOH are present in 90.0 g of NaOH?  To solve this, divide 90.0 g by 40 g/mol or multiply 90.0 g by the reciprocal of 40 g/mol (1 mol/40 g) to get the unit (g) to cancel out.  90g NaOH ⋅ 1 mol40g=2.25 mol NaOH  The final answer is 2.25 moles in 90g of NaOH.

Practice  How many moles is 39 grams LiF equivalent to?