Molar Weight Avogadro’s Number made easy!

Warm Up 1.How do you count large numbers of atoms and molecules? 2.What is a mole? 3.How many things are in a mole? 4.What is Avogadro’s number?

Warm Up 1.What is a mole used for? 2.What is Avogadro’s number? 3.Given 3.5 moles of cobalt, what is its molar mass? 4.Given 5 moles of zinc, what is its molar mass? 5.Given 10 moles of phosphorus, what is its molar mass? 6.You have 400 grams of manganese, how many moles do you have? 7.You have 250 grams of manganese, how many moles do you have? 8.You have 70 grams of lithium, how many moles do you have?

Homework Due 2/18: practice problems 1-3, pg 311 practice problems 4, page assessment 5-8, page 312 Due 2/19: practice problems 12 a-d, page 316 practice problems 14 a-e, page 318 Due 2/22: practice problems 27-29, page 323 practice problems 30 a-e, page 324

Warm Up 1.Given 12 moles of chromium, what is its molar mass? 2.You have 1000 grams of strontium, how many moles do you have? 3.Given 25 moles of water, what is its molar mass? 4.You have 500 grams of NaOH how many moles do you have? 5. Given 50 moles of MgCl 2, what is its molar mass? 6.You have 200 grams of Mn 2 Se, how many moles do you have?

Warm Up 1.What is the mass of sulfur if you have 2.3 x atoms of sulfur. 2.What is the mass of carbon if you have 5.6 x atoms of carbon. 3.What is the mass of iron if you have 1.8 x atoms of iron. 4.What is the mass of fluorine if you have 12.9 x atoms of fluorine. 5.What is the mass of chlorine if you have 6.7 x atoms of chlorine.

Warm Up 1.What is Avogadro’s number? 2.Given 3.5 moles of cobalt, what is its molar mass? 3.You have 250 grams of manganese, how many moles do you have? 4.You have 200 grams of Mn 2 Se, how many moles do you have? 5.What is the mass of fluorine if you have 12.9 x atoms of fluorine.

Warm Up Please write Lewis Dot Structures for the following: 1.Carbon 2.Nitrogen 3.Argon 4.Iron 5.Copper

Warm Up 1.Calculate the percent composition for the following: NaHCO 3. 2.Given 200 grams of the above compound, what is the mass of each element? 3.Calculate the percent composition for the following: H 2 SO 3. 4.Given 200 grams of the above compound, what is the mass of each element? 5.Calculate the percent composition for the following: H 2 S 2 O 8. 6.Given 200 grams of the above compound, what is the mass of each element?

Warm Up Balance the following equations and identify the type of chemical reaction involved: ____ ZnCl 2 + ____ KOH  ____ Zn(OH) 2 + ____ KCl ____ Ba(OH) 2  ____ BaO + ____ H 2 O ____ K + ____ H 2 O  ____ KOH + ____ H 2 ____ NaBr + ____ Cl 2  ____ NaCl + ____ Br 2 ____ MgCO 3  ____ MgO + ____ CO 2 ____ ZnCl 2 + ____ KOH  ____ Zn(OH) 2 + ____ KCl

Packaging People have all kinds of ways of packaging things. Eggs come in dozens And paper comes in reams

????????? No one knows why hot dogs come in packs of 10 and buns come in packs of 8!

The Mole Chemists even have a standard way to package atoms. Because atoms are so small the number of atoms per package is very large.

How many atoms are in a Standard Package? The standard container for atoms holds X atoms. This number is referred to by chemists as Avogadro’s number for Count Amedeo Avogadro that invented it.

Mass versus Quantity Do all moles of a particular element weigh the same? No!! Larger heavier elements have a greater molar weight that smaller atoms, just like 10 bowling balls weighs more than ten marbles.

Molar Mass The mass (in grams) of one mole of a substance is called its molar mass. The molar mass of an element in a.m.u.’s is the same as its molar weight in grams.

Example of molar mass For example, carbon’s atomic mass is a.m.u.’s while its molar weight is grams.

Using Mass to Count You work in a candy store and receive a new shipment on gum balls. You are asked to put them in bags of ten. The total weight of the candy is 10 kg’s. If each gum ball weighs 20 grams, how many bags do you need?

Gum Ball Answer 10 kilograms is 10,000 grams. Each gumball weighs 20 grams, so 10,000/20 = 500 gumballs. Each bag will hold 10 gumballs so you’ll need (500/10) or 50 bags to pack all the gumballs.

Example #2 You have 5.5 moles of iron. The molar mass of iron is g/ mol Fe. What is the mass of the iron that you have?

Solution to Example #2 5.5 moles Fe X g/mole Fe = 307 g Fe 1 mole Fe

Problems for You Convert the following into weight in grams: moles of sulfur, S moles of calcium, Ca mole of carbon, C moles of copper, Cu

Last Problem Given 352 grams of Fe iron), how many moles of iron do you have?

Solution 352 g Fe X 1 mole Fe = 6.30 moles Fe g Fe