Chapter 3 (CIC) and Chapter 3, 18 (CTCS) Read in CTCS Chapter 3.4, 6, 7, and 18.4 (pgs. 697-699)...
-
Upload
lynette-wells -
Category
Documents
-
view
215 -
download
2
Transcript of Chapter 3 (CIC) and Chapter 3, 18 (CTCS) Read in CTCS Chapter 3.4, 6, 7, and 18.4 (pgs. 697-699)...
Chapter 3 (CIC) and Chapter 3, 18 (CTCS)
• Read in CTCS Chapter 3.4, 6, 7, and 18.4 (pgs. 697-699)
• Problems in CTCS: 3.29, 31, 33, 35, 39, 41, 59, 63, 69, 71, 73, 79, and 18.27
How Much CO2 is 3 bmt of C?
• Several ways to solve (%C in CO2 and stoichiometric relationships)
Q: What is the %C in CO2?
A: 27.3%
• This is equivalent to dividing 3 by 0.273 (27.3%)
22
3 bmt C 44 bmt CO = 11 bmt CO
1 12 bmt C
Stoichiometric Relationships• C + O2 CO2
• Since a bmt is so much larger than an amu, it is helpful to work on a larger scale than an amu – such as grams
• If a 12C atom weighs 12.0000…amu by definition, how many 12C atoms does it take to weigh 12.000…g? 6.02 x 1023 (Avogadro’s number)
• Dozen, Gross, Ream, Mole
12 -24
23
C atom 12 g 1.66 x 10 g =
12 amu 6.02 x 10 C atoms amu
Inverted: 6.02 x 1023 amu/g
• How big is Avogadro’s number?
• 1 mol of seconds = 4 million times as long as Earth has existed
• We use Avogadro’s number to count individual atoms, molecules, electrons, etc.
62 2 2
262 2
3 bmt C 10 g C 1 mol C 1 mol CO 44 g CO 1 bmt CO = 11 bmt CO
1 1 bmt C 12 g C 1 mol C 1 mol CO 10 g CO
Stoichiometry LabFor MgCO3 we were finding ~ 0.40 g CO2 released. Had we not known it was a carbonate, could we have figured it out knowing that 0.73 g of HCl was used in the reaction?
CO32- + 2 HCl H2O + CO2 + 2 Cl-
HCO3- + HCl H2O + CO2 + Cl-
How many g of that 0.40 g is due to C (27.3%)?
2 22
2
0.73 g HCl 1 mol HCl 1 mol CO 44 g CO = 0.44 g CO
1 36.5 g HCl 2 mol HCl 1 mol CO
2 2
2 2
0.40 g CO 1 mol CO 1 mol C 12 g C = 0.11 g C
1 44 g CO 1 mol CO 1 mol C
How do you know it was Mg?• Suppose the slope of the line in the 1st week’s
data had been 0.5g CO2/1 g XCO3.
• ? = 88 g XCO3 and of that 88g, 44 + 16 (or 60g) of it was due to the CO3. This means that 28 g of it was due to X. If X was an alkaline earth metal then it must mass 28g. If X was an alkali metal X must mass 14 g because the formula is X2CO3.
2 2
3 3
0.50 g CO 44 g CO =
1 g XCO ? g XCO
Q: If volcanoes release 19 mmt SO2, how much S is “combusted”?
A: 9.5 mmt S
Q: If a lighter holds 5.0g of butane (C4H10), how many grams of CO2 are produced upon combustion?
A: 15 g CO2
g (reactant) mol (reactant) mol (product) g (product)
Limiting ReagentCO3
2- + 2 H+ H2O + CO2
• When adding small amounts of the carbonate a pink solution remained. – What was the limiting reagent? – What was the excess (xs) reagent? – Could you tell by looking at the solution?
• When large amounts of carbonate were added, a white solid and colorless solution appeared. – What was the limiting reagent? – What was the excess (xs) reagent? – Could you tell by looking at the solution?
• At what point on the graph could you use the stoichiometric relationships?
Percent Yield (actual/theoretical x 100)• In reality, we ended up getting about 0.35 g CO2
from the MgCO3 instead of the 0.44 g that is the theoretical amount. See next slide for the graph!
Q: What is the percent yield of CO2 that was obtained?
A: 80%
• What does this mean?– HCl concentration was not 0.73 g– A poor yielding reaction is not suitable for this lab
Stoichiometry Laby = 0.3453x
R2 = 0.724
y = -0.0013x + 0.3382
R2 = 0.0004
0
0.1
0.2
0.3
0.4
0 0.5 1 1.5 2 2.5 3 3.5 4
g XCO3
g C
O2
Other Gases and What We Know• CH4 is 30x as effective as a greenhouse gas as CO2 but
its’ concentration is only at 1.7 ppm• CFC’s – 25,000x effective and [CFC] is at 0.28 ppb• Modeling earth’s Temp is still crude• We know
– CO2 increases global Temp
– [CO2] increased over the last century
– [CO2] increased due to human activity
– Global Temp increased over last century
• Uncertain about– CO2 and other gases are responsible for increased Temp
– Avg global Temp will continue to increase as anthropogenic greenhouse gases increase
What Should We Do?• Act now! Is the cure worse than the disease?
– Fertilize ocean with iron to increase phytoplankton– Release S containing compounds into air
– Pump CO2 to bottom of ocean
– Pollution Rights• US has a great head-start over undeveloped countries
• Study the problem more
• Nothing – It’s inevitable - Adapt– Fossil fuels are too valuable to just combust