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- 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
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- 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
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3
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4
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- 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
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a very small no.
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5
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- 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
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6
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- 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…...
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7
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8
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- # moles X = #g X/molar mass X
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9
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- 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?
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10
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- 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?
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11
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- 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.
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12
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- The chemical formula:
- MgO (ion pair)
- H2O
- C12H22O11
- Ca3(PO4)2
- CuSO4.5H2O vs
CuSO4
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13
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- 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 =
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14
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- In general we talk about
- moles for covalent compounds
- formula units rather than moles of ionic compounds.
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15
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- Mass of one mole of NH3:
- Mass of 6.022 x 1023
molecules of NH3 is
- Mass of one molecule of NH3 is.
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16
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- 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
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17
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- 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.
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18
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- 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
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19
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- 5.40. How many moles are in 50.0 g of
- A. CS2
- B. Al2(CO3)3
- C. Sr(OH)2
- D. LiNO3
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20
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- 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?
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21
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- 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
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22
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- mercury + oxygen ---> mercury(II)oxide
- 10.03g ? 10.83g
- Easier to use symbols for chem eqns.
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23
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- 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
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24
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- 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.
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25
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26
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27
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- 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.
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28
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- 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
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29
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- hydrogen + nitrogen g ammonia
- 1. write the symbols for the species in the rxn
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30
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- 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.
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31
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- 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
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32
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- C2H6 + O2 g CO2 + H2O
- H2O2 g H2O + O2
- C2H5OH + O2 g CO2 + H2O
- KOH + H3PO4 g K3PO4 + H2O
- N2O5 g N2O4 + O2
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33
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- NH4NO3 g N2O +
H2O
- NH4NO2 g N2 + H2O
- Be2C + H2O g Be(OH)2 + CH4
- NH3 + CuO g Cu + N2 + H2O
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34
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- S2Cl2(s) + NH3(g) g
N4S4(s) + NH4Cl(s) + S8(s)
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35
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- 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.
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36
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- 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
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37
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- 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.
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38
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39
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- 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?
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40
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- 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?
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41
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- 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
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42
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43
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- How many grams of Al2O3 can be produced from 15.0
g Al?
- 4 Al(s) + 3O2(g) g 2Al2O3(s)
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44
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- 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?
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45
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- 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.
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- 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
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- 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
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48
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- 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?
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49
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- If the % yield of Fe2O3 in problem was 90.0% what
was the actual yield of Fe2O3?
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50
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- A 3.5 g sample of water reacts with PCl3 according to
: 3H2O + PCl3 g H3PO3 +
3HCl.
- How many grams of H3PO3 are produced?
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Notes
