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| | From:  Zurconium2 (Original Message) | Sent: 3/25/2006 10:52 PM |
<LABEL for=webct2_1922190052>The power goes out right before you are set to cook dinner. You find your old camping stove (that uses propane gas as fuel) and you have your charcoal grill in the backyard (charcoal is 100% carbon). You only have one match. Assume you have the same amount of moles of each fuel. Which is a better cooking source? (hint: this is a Thermochemistry question!).</LABEL>
For this I thought of heats of combustion of the two and propane is greater. But the one match part made me think that the other chapters we looked at might come into play, like vapor presuures etc. But the chapter on thermochemistry is wanted.
What are your thoughts? |
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| | | From: ·Steve· | Sent: 3/26/2006 2:27 AM |
Seems like the one match part is irrelevant, since you could light a splint or something from one fire and light the other. But, try to light a piece of charcoal with a match! (You need lighter fluid!) So I think the question just wants to know which combustion will produce the most energy, the combustion of one mole of propane or one mole of carbon. All you have to do is compare DH° for the following reactions:
C3H8 (g) + 5 O2 (g) ---> 3 CO2 (g) + 4 H2O (g)
and
C (s, graphite) + O2 (g) ---> CO2 (g)
Steve |
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Thanks Steve. Any ideas for these? A Tums tablet (which some people take to boost their calcium intake) contains 500. mg calcium carbonate. An article on diet warns: "Always read the label to make sure you're not getting more carbonate than elemental calcium." Are you? Is there anything you can do about it? Explain your answers. A newspaper columnist wrote the following explanation of why baseball players hit more home runs during hot, humid weather than during cool, dry weather: "Hot air molecules are bigger than cold air molecules so there's less friction."
(1) Why might the reporter think hot air molecules are bigger than cold ones?
(2) The right answer to why baseballs go farther in humid weather involves density, but is it possible to argue this just using partial pressure? Explain whether you can or cannot. |
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| | | From: ·Steve· | Sent: 3/26/2006 7:37 AM |
Well, looking at the formula of calcium carbonate, you can see that every formula unit of CaCO3 contains equal numbers of Ca2+ ion (the "elemental calcium") and CO32- ion. This is in terms of moles. In terms of grams, every mole of CaCO3 contains about 40.077 g of Ca2+ and 60.010 g of CO32-. So in mole units the amounts are the same, but in gram or milligram or any mass unit the amount of carbonate is greater! Since the formula is fixed, there would be nothing you could do about it unless your calcium source is something other than calcium carbonate.
For some ideas about your other question, visit the link below!
Steve
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