CHEM 120: Introduction to Inorganic Chemistry

	Instructor: Upali Siriwardane (Ph.D., Ohio State University)
	CTH 311, Tele: 257-4941, e-mail: upali@chem.latech.edu
	Office hours: 10:00 to 12:00 Tu & Th ;  8:00-9:00 and 11:00-12:00  M,W,& F

Chapters Covered and Test dates

	Tests will be given in regular class periods  from  9:30-10:45 a.m. on the following days:
	September 22,     2004 (Test 1): Chapters 1 & 2
	October 8,           2004(Test 2):  Chapters  3, & 4
	October 20,         2004 (Test 3): Chapter  5 & 6
	November 3,        2004 (Test 4): Chapter  7 & 8
	November 15,      2004 (Test 5): Chapter  9 & 10
	November 17,      2004 MAKE-UP: Comprehensive test (Covers all chapters
	Grading:
	[( Test 1 + Test 2 + Test3 + Test4 + Test5)] x.70 + [ Homework + quiz average] x 0.30 = Final Average
	5

Chapter 5. Calculations and the Chemical Equation

The mole concept and atoms

	In ch 1 we learned that 1 amu = 1.661 x 10-24 g
	So if the average mass of a gold atom is196.97 amu x 1.661 x 10-24 g  = 3.27 x 10-22 g            1 amu
	a very small no.

"Where did I get the..."

	Where did I get the 196.97 anu for the mass of one Au atom?
	From the ____________________!!!
	If I write amu after these nos. it implies that I have the mass of ______ atom of that element (in amu).
	But 3.27 x 10-22 g is too small an amt to work with in the lab.
	What to do?
	Scale up to quantities that we can handle by

Avogadro’s number

	Defining  one mole (mol) as amt of substance that contains as many elementary entities  (atoms, molecules, ions , etc) as there are in atoms in exactly 12 g of the carbon-12 isotope. This is determined experimentally and is…...

Slide 7

Useful relationship

	# moles X = #g X/molar mass X

Some problems

	How many atoms are there in 5.10 moles of sulfur? What’s the mass of 5.10 moles of S?
	How many moles of calcium atoms are in 1.16 x 1024 atoms of Ca? How many grams?

"Which of the following has..."

	Which of the following has more atoms: 1.10g of hydrogen atoms or 14.7 g of chromium atoms?
	How many moles are in 0.040 kg Na?

"What’s the mass,"

	What’s the mass, in grams, of one atom of potassium?
	One atom of some element has a mass of 1,45 x 10-22 g. Identify the element.

Compounds

	The chemical formula:
	MgO  (ion pair)
	H2O
	C12H22O11
	Ca3(PO4)2
	CuSO4.5H2O  vs  CuSO4

The mole concept applied to compounds

	The formula weight of a species is the sum of atomic masses (amu) of the atoms in a species.
	Formula weight of NH3
		For an ionic compound
		MgF2 =

"In general we talk about"

	In general we talk about
	moles for covalent compounds
	formula units rather than moles of ionic compounds.

Molar mass

	Mass of one mole of NH3:
	Mass of 6.022 x 1023 molecules of NH3 is
	Mass of one molecule of NH3 is.

"Mass of one mole of..."

	Mass of one mole of MgF2 is
	Mass of one formula unit  of MgF2 is
	Mass of 6.022 x 1023 formula units of MgF2 is

"Calc the molar"

	Calc the molar  mass of Ca(NO3)2.
	Calc the molar mass of a compound if 0.372 mol of it has a mass of 152g.

"5.38."

	5.38. How many grams of each are required to have 0.100 mol of
	A. NaOH
	B. H2SO4
	C. C2H5OH
	D. Ca3(PO4)2

"5.40."

	5.40. How many moles are in 50.0 g of
	A. CS2
	B. Al2(CO3)3
	C. Sr(OH)2
	D. LiNO3

"Calc the no."

	Calc the no. of C, H, and  O atoms in 1.50 g of glucose (C6H12O6).
	What is the average mass of one C3H8 molecule?
	What is the mass of 5.00 x 1024 molecules of NH3?

Law of conservation of mass

	Mass is neither created nor destroyed in an ordinary chemical rxn.
	Or the sum of the masses  of the reactants is equal to the sum of the masses of the products

"mercury + oxygen ---> mercury(II)oxide"

	mercury + oxygen ---> mercury(II)oxide
	10.03g       ?                     10.83g
	Easier to use symbols for chem eqns.

"reactants g"

	reactants g  products
	lhs            rhs
	may indicate physical state by (s), (g), (l), (aq)-aqueous solution
	Remember that H2,N2,O2,F2,Cl2,Br2,I2 occur as diatomics in nature and are used as diatomics in chemical eqns

"To balance:"

	To balance: Have to have same no of each kind of atom on both sides of the eqn. The bonding arrangement changes, but the no of each kind of atom doesn’t change.

Slide 25

Slide 26

Balancing chemical eqns

	Use correct formulas for the reactants and products (if word eqn at start)
	Balance by putting coefficients (nos) in front of the formulas. You may not change the formulas! These coefficients are called the stoichiometric (measure of mass) coefficients.
	By convention use the lowest set of whole no. coefficients to balance.

"Start by balancing elements that..."

	Start by balancing elements that appear only once on each side of the equation
	Balance remaining elements
	Check your balanced equation!
	To predict products--do an experiment

To balance

	hydrogen + nitrogen  g ammonia
	1. write the symbols for the species in the rxn

"Now figure out how to..."

	Now figure out how to get the same no of atoms of each kind on both sides by using whole no coefficients in front of the species.
	As       H2  + _N2 g NH3, then
	H2  + _N2 g _ NH3,  then
	_ H2  +  _N2 g _ NH3
	Now have _ H’s, _N’s on both sides and the lowest set of whole no coefficients have been used.  The equation is balanced.

"3H₂ + N₂ g 2NH₃"

	3H2 + N2 g 2NH3
	3 mol of H2 reacts with 1 mol of N2 to form 2 mol of NH3
	3 molecules of H2 reacts with 1 molecule of N2 to form 2 molecules of NH3
	6H + 2N reacts to give 6H and 2N
	6g of H2 reacts with 28 g of N2 to form 34g of NH3
	Note that

Balance

	C2H6 + O2 g CO2 + H2O
	H2O2 g H2O + O2
	C2H5OH + O2 g CO2 + H2O
	KOH + H3PO4 g K3PO4  + H2O
	N2O5 g N2O4 + O2

Balance

	NH4NO3 g N2O  +  H2O
	NH4NO2 g N2   + H2O
	Be2C + H2O g Be(OH)2 + CH4
	NH3 + CuO g Cu + N2 + H2O

Balance

	S2Cl2(s) + NH3(g)  g  N4S4(s) + NH4Cl(s) + S8(s)

Calculations using the chemical eqn

	Quantitative study of reactants and products in a chemical reaction
		How much product will be formed?
		How much reactant is needed?
		Use coefficients in a balanced equation to convert between moles of different substances in a chemical reaction.

Chemical Reaction

	3H2(g)  +    N2(g) ------>  2NH3(g)
	3 mol H2 (reactant) = 1 mol N2 (reactant)  consumed
	3 mol H2 (reactant) =  2 mol NH3 (products) produced
	1 mol N2 (reactant) = 2 mol NH3 (products) produced
	3 x 2 (6) g H2 (reactant) = 1x 28  (28)mol N2 (reactant)  consumed
	3 x 2 H2 (6) (reactant) =  2x 17 (34) NH3 (products) produced
	1 x 28 (28) g N2 (reactant) = 2 x 17 (34) NH3 (products) produced

Chemical reactions

	Hydrogen reacts with nitrogen to form NH3.
	theoretically  it is should be that when 6 g of hydrogen reacts completely with  28 g of nitrogen,  34 g of ammonia is formed.
	However in real chemical reactions actual __ g of hydrogen reacting with __ g of nitrogen,  __ g of ammonia is produced need be experimentally determined.

2H₂ + O₂ g 2H₂O

2H₂ + O₂ g 2H₂O

	How many moles of H2  is needed to completely react with19.8 mol O2?
	How many moles of H2O are formed when 25.4 mol of H2 react?

2H₂ + O₂ g 2H₂O

	How many moles of H2 react with 38 g of O2?
	What mass of H2O is formed when 59.0g of H2 reacts completely with O2?  How much O2 reacted in this case?

Mass relationships
in chemical equations

	Mole-to-mole conversions
		use mole ratios as conversion factors
	Mass-to-mole and mole-to-mass conversions
		use molecular weights as conversion factors
	Mass-to-mass conversions
		do in multiple steps

General prescription

Problems

	How many grams of Al2O3 can be produced from 15.0 g Al?
	4 Al(s) + 3O2(g) g 2Al2O3(s)

"C₃H₈ +"

	C3H8 +  O2 g CO2 + H2O    balance
	How many mol of O2 does it take to completely burn 7.0 mol of C3H8?
	How many mol each of CO2 and H2O are produced?
	How many grams of oxygen does it take to completely burn 25.0 g of C3H8?
	How many grams each of CO2 and H2O are produced when 25.0 g of C3H8 is burned?

"A 4.00 g sample of..."

	A 4.00 g sample of Fe3O4 reacts with O2 to produce Fe2O3.
	4Fe3O4(s) + O2(g)g   6Fe2O3(s)
	Determine the no. of grams of Fe2O3 produced.

Theoretical and percent yield

	How good an experimentalist are you?
	What if 100% of reactants are not converted to desired products?
	Frequently happens because of “side reactions” (other products), handling, etc.
		100% amount is theoretical yield
		Amount obtained is actual yield

"Theoretical yield - amount of..."

	Theoretical yield - amount of product that would result if all limiting reagent gave only product
	Actual yield - the amount of product actually obtained from a reaction (almost always less than the theoretical yield)
	Percent yield - calculated by
	% yield = actual yield     ´ 100%
	theoretical yield

"Theoretical yield is what we..."

	Theoretical yield is what we calculate assuming 100% conversion of reactants to products.
	In the combustion of 33.5g of C3H6, 16.1 g of H2O is isolated. What is the percent yield?

"If the % yield of..."

	If the % yield of Fe2O3 in problem was 90.0% what was the actual yield of Fe2O3?

"A 3.5 g sample of..."

	A 3.5 g sample of water reacts with PCl3 according to : 3H2O + PCl3 g H3PO3 + 3HCl.
	How many grams of H3PO3 are produced?