Title: When You Come In Please Pick Up
1When You Come In Please Pick Up
- Initial Soda Ash Questions worksheet
2Percentage CompositionIsotopes, Empirical
Molecular Formulas
- Edward A. Mottel Jeffrey E. Froyd
- Department of Chemistry and Integrated,
First-Year Curriculum in Science, Engineering and
Mathematics
3Atomic Composition
- Protons, neutrons and electrons
- Ions, cations and anions
- Isotopes
- Resources
- Zumdahl Chapter 2.1-2.4, 3.1-3.5
4Isotopes of Silver
- Silver has two common isotopes
- silver-107 and silver-109
- Silver-107 has 47 protons and 60 neutrons
Why are these atoms considered to be isotopes of
each other?
What is the same and different about each isotope?
5The element silver (Ag) has two naturally
occurring isotopes, 107 and 109. Its average
atomic mass is 107.868. Calculate the mass of
the heavier isotope
106.905
51.82
6The element silver (Ag) has two naturally
occurring isotopes, 107 and 109. Its average
atomic mass is 107.868. Calculate the mass of
the heavier isotope
106.905
51.82
- (mass 107Ag)( 107Ag)
- (mass 109Ag)( 109Ag) avg. atomic mass
7Solve Equation
- soln solve((106.9050.5182) m109Ag(1 -
0.5182)) 107.868, m109Ag) - soln 108.9037547
8Chemical Analysis andEmpirical Formulas
- Percentage composition by mass of a compound
- Determination of the empirical formula from
percentage by mass information - Empirical versus molecular formulas
9Percentage Composition
What is the percentage silver in silver nitrate?
- Silver Nitrate AgNO3
- Molar Mass 1(AW Ag) 1(AW N) 3(AW O)
- ( Ag) 1(AW Ag)/(Molar Mass)
- ( N) 1(AW N)/(Molar Mass)
- ( O) 3(AW O)/(Molar Mass)
10Empirical Formula
- Empirical formula problems are the reverse of
percentage composition problems. - A compound that contains only carbon, hydrogen
and oxygen is 48.38 C and 8.12 H. What is the
empirical formula of this compound?
11Empirical Formula CnCHnHOnO
- eqn1 mass nC12.01nO16.00nH1.008
- eqn2 nC12.01/mass 0.4838
- eqn3 nO16.00/mass (1 - 0.4838 - 0.0812)
- eqn4 nH1.008/mass 0.0812
- sln solve(eqn1, eqn2, eqn3, eqn4, mass, nH,
nC, nO) - sln nO .6749108619 nC, mass 24.82430757
nC, nH 1.999735887 nC, nC nC - (CH2O2/3)nC -----gt (C3H6O2) nU
12Empirical vs. Molecular Formulas
- Empirical Formula (C3H6O2) nU
- Possible Molecular Formulas
- C3H6O2 nU 1
- C6H12O4 nU 2
- C9H18O6 nU 3
What would be the molecular formula if the
approximate MW is 150 gmol-1?
13Carbohydrates
- Carbohydrates are compounds with the general
formula Cm(H2O)n where m is typically 5 or
greater and nltm. - Show that sucrose C12H22O11 is a carbohydrate.
- Do all carbohydrates have the same percentage
composition for each element?
14Sodium Bicarbonate Thermal Decomposition
- Sodium bicarbonate decomposes when heated to form
solid sodium carbonate, water vapor and carbon
dioxide. - If 2.00 grams of sodium bicarbonate is heated and
completely decomposed, what will be the mass of
the remaining solid? - In your group decide on the sequence of steps
needed to solve this problem.
15Sodium Bicarbonate Thermal Decomposition
- Process
- Balance equation
- Identify a pathway to go from mass of reactant to
mass of product. - Calculate the answer.
- Check your answer -- does it seem reasonable?
16Sodium Bicarbonate Thermal Decomposition
- Sodium bicarbonate decomposes when heated to form
solid sodium carbonate, water vapor and carbon
dioxide. - If 2.00 grams of sodium bicarbonate is heated and
is 60 decomposed, what will be the mass of the
remaining solid? - In your group decide on the sequence of steps
needed to solve this problem.
17Sodium Bicarbonate Thermal Decomposition
0.76 g
2.00 g
0.80 g
1.56 g
18Sodium Bicarbonate Thermal Decomposition
- A little harder problem
- If 2.00 gram sample of sodium bicarbonate is
heated and has a mass of 1.56 grams after
heating, what is the percentage converted
(percentage yield)? - Hint How many moles of CO2 and H2O are produced?
How many moles of NaHCO3 have decomposed?
19(No Transcript)