# What does the little number below each

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What does the little number below each
Element mean? What are its’ units? amu/atom

one amu is defined as 1/12th
What is an amu one amu is defined as 1/12th of 12C

Average atomic mass or atomic weight is determined by a mass spectroscope.
example: Analysis of a sample of carbon was found to have the following isotopes 12C – % 13C – % 14C – % What is the atomic weight of Carbon

12C – (11.999) (.973) = 13C – (12.998) (.026) = 14C – (13.966) (.0010) =

How high could you stack a mole of sheets of paper?
How much is a mole? How high could you stack a mole of sheets of paper?

How much would a mole of iron weigh? Could you lift it?
Look on the back inside cover for amu and mole x 1023 atoms of Fe 55.85 amu x g* =55.85 g 1atom of Fe 1 amu

What is the Mole? One mole is equal to the number of carbon atoms in exactly grams of C-12: 6.02 x 1023 atoms

The Shopping Mole x g/ mole 22.4 L / mole
# of atoms or molecules 6.02 x atoms or molecules/mole Mole x g/ mole 22.4 L / mole Mass of atom or molecule volume of gas The Shopping Mole

Calculate the numbers of atoms of cesium found in 3.57 moles of cesium
Calculate the numbers of atoms of cesium found in 3.57grams of cesium Calculate the mass of 4.82 x 1023 atoms of cesium

1. Calculate the mass of 4.65 moles of (NH4)2S
Calculating the molar mass of a compound (NH4)2S 1. Calculate the mass of 4.65 moles of (NH4)2S 2. Calculate the numbers of atoms of nitrogen found in 3.57grams (NH4)2S 3. Calculate the mass of nitrogen in 3.76 x 1024 formula units of (NH4)2S

Determining Percent Composition of Compounds
Given the compound: Al(HPO3)3 What are the percent compositions of each of the atoms from which the above compound is constructed? Mass of Aluminum= 1 mol Al 26.9 grams = 26.9g Al mole of Al Mass of hydrogen = 3 mols H 1.01 gram = H mole of H 266 g Al(HPO3)3 Mass of Phosphorus = 3 mols P 30.9 gram = g P mole of P Mass of oxygen = 9 mols O 16.0 gram = 144 g O mole of P

10.1% Mass percent of Al: 1.13% Mass percent of H: 34.8%
mass of Al 26.9 g 10.1% = x 100 = Mass percent of Al: mass of Al(HPO3)3 266 g mass of H 3.03 g x 100 1.13% = Mass percent of H: = mass of Al(HPO3)3 266 g mass of P 92.7 g 34.8% x 100 Mass percent of P: = = mass of Al(HPO3)3 266 g mass of O 54.1% 144 g = = x 100 Mass percent of O: 266 g mass of Al(HPO3)3

Empirical formula A compound is composed of Cl 71.65% and C 24.27% and H 4.07% what is the empirical formula? The Molar mass is 98.96g/mole, what is the molecular formula?

0.255 g isopropyl alcohol is combusted
Determining the Empirical Formula of a Compound Using Combustion Analysis Combustion Analysis 0.255 g isopropyl alcohol is combusted mass difference of H2O absorber = g mass difference of CO2 absorber = g

mass difference of H2O absorber = 0.306 g
mass difference of CO2 absorber = g 1 mole CO2 12 g C grams of C: g CO2 = 0.153g C 44 g CO2 1 mole CO2 1 mole H2O 2.02 g H grams of H: g H2O = g H 18 g H2O 1 mole H2O grams of O: g g g H = g

Assume that the empirical formula for the compound is C3H8O
1 mol C 1 C: g C = 2.97 = mol C 12 g C 0.0043 1 mol H 1 H: g H = 7.91 = mol C 0.0043 1.01 g H 1 1 mol O O: g O = 1.00 = mol O 0.0043 16 g O Assume that the empirical formula for the compound is C3H8O

Ascorbic acid (Vitamin C) contains 40. 92 percent C, 4
Ascorbic acid (Vitamin C) contains percent C, 4.58 percent H, and percent O by mass. What is the empirical formula of ascorbic acid? Ethylene glycol, the substance used in automobile antifreeze, is composed of 48.7 % C, 9.7 percent H, and 51.6 percent O by mass. Its molar mass is 62.1 g/mol. (a) What is the empirical formula of ethylene glycol? (b) What is the molecular formula

So What is Stoichiometry?
mass of A in g mole 3(moles C) C g = mass C A g 1(moles A) mole 1A + 2B → 3C + 4D

Na2SO3(aq) + 2AgNO3(aq)  Ag2SO3(s) + 2NaNO3(aq)
If 3.4 g of silver nitrate is mixed w/ excess sodium sulfite, what would be the theoretical yield for silver sulfite? in moles in formula units in L at STP in grams

Na2SO3(aq) + 2AgNO3(aq)  Ag2SO3(s) + 2NaNO3(aq)
If 3.4 g of silver nitrate is mixed sodium sulfite, how many grams of sodium sulfite would you need to react completely?

Na2SO3(aq) + 2AgNO3(aq)  Ag2SO3(s) + 2NaNO3(aq)
If 4.5 g of sodium sulfite is mixed w/ excess silver nitrate, what would be the theoretical yield for silver sulfite? What would be the percent yield if 4.1g was produced in the lab?

Na2SO3(aq) + 2AgNO3(aq)  Ag2SO3(s) + 2NaNO3(aq)
If 4.3 g of silver nitrate is mixed w/ 3.2g sodium sulfite, what would be the theoretical yield for silver sulfite? How much of the excess reagent is left over?

Using Stoichiometry in the Laboratory
Na2SO3(aq) + 2AgNO3(aq)  Ag2SO3(s) + 2NaNO3(aq) 20 ml 0.12 M 20 ml 0.35 M 1. How many grams of silver sulfite would be produced? 2. What would be the molarity of the sodium nitrate?

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