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Dicentra last won the day on June 12 2013

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About Dicentra

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  • Birthday 03/02/1972

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  1. Some ideas to look into:
  2. You're in excellent company, Wendy. The BBC made the exact same mistake. 😄
  3. You're welcome! It makes me so happy when something clicks for a student in chemistry. 🙂 You tell your DS that chemistry can be tough and folks at Meriwether Homeschool are super smart! 🙂
  4. What you're solving for in your last line is the enthalpy of formation of CS2 from its elements. 🙂 The question is asking how much energy it would take to make CS2 from graphite and H2S which is a slightly different proposition than making it from its elements. To answer the question we don't need to know the enthalpy of formation of H2S (which is what I'm assuming the -20.5kJ is) so that's a bit of misdirection. The equation says that it requires 157.9kJ of energy to be put in to make 1 mole of CS2 (because the coefficient is 1 in the balanced equation) from 1 mole of graphite and 2 moles of H2S. If we convert 100.0g of CS2 to moles we get 100.0g / 76.139g/mol = 1.313mol of CS2. Since we know that 157.9kJ is required for 1 mole, then 157.9 kJ/mol x 1.313 mol = 207.3 kJ is required to make 100.0g of CS2 from graphite and H2S. What you were solving for in your last line is the energy required to make 1 mole of CS2 from its elements or its enthalpy of formation which would be this: C (graphite) + 2 S (rhombic) --> CS2 The reaction given in the question gives a different energy for the making of CS2 because you also need to take into account the energy required to break apart H2S in order to create the CS2. So the making of 1 mole of CS2 from its elements would take 116.9kJ but the making of 1 mole of CS2 using the reaction in your question would take 157.9kJ because of the added energy needed (the 41.0kJ) to first break apart the H2S before we can make the CS2. And yes to your second post. 🙂 When we write energy as a term in a chemical equation (which isn't exactly "legal" in chemistry but we do it to help understanding), then if a reaction is endothermic the energy term will be written as a reactant - think of it as energy having to be put in or added to the reaction to make it go. Things that are "put in" to a chemical reaction are the reactants. If a reaction is exothermic, then the energy term will be written as a product because energy is being produced or given off.
  5. So maybe KILL-oh-meeter is a distinctly weird Canadian thing, not a Brit thing. 🙂 That's OK. We Canadians tends to just be generally weird all around. 😉 😄
  6. Are you close to the border, AB? We're right on the border and lots of people here use both and many will say kill Ah meter (US style pronunciation). I think I tend to say KILL oh meeter because I teach science and spend whole lessons going over the metric prefixes and kill Ah gram just sounds funny. 🙂
  7. Well - I'll be the pedantic Canadian about this and say that "KILL oh meeter" is correct and the other pronunciation is not. 🙂 "Kilo-" is a prefix in the metric system so you can have kilograms, kiloliters, kilowatts, etc. If you say the prefix by itself, it's "KILL oh", not "kill AH". 🙂 Although a true Canadian would probably just give the distance in "klicks" as in I live about 350 klicks from Winnipeg. But that might be a regional prairie thing. 😉
  8. Sounds good, gstharr! Let me know if you have any questions about the course between now and then!
  9. Hmmm... Okay - just talked to my dad who was a Class A mechanic for 40+ years (which is why I know a little about cars :)). He says to give the connections to the battery and also the connections on the starter a good cleaning and then coat them with dielectric grease. That should stop further corrosion from happening. If that doesn't work, he also suggested replacing the fuel filter - if the filter is gummed up, the engine won't be getting the right fuel/air ratio and may have trouble starting. If that doesn't work, he suggested having someone look at the timing. He also said it could be an electrical issue - maybe a loose connection somewhere other than at the battery connection. That might cause some fluctuations in voltage in the system and be causing some of the battery issues. Finding a loose connection can be a notorious pain in the hind end, though - it could be ANYWHERE in the electrical system of the vehicle and it's difficult to find and pin down. Hope that helps!
  10. What's the expression? When life gives you lemons... 😄 Make lemonade!! Seriously, the fact that you can grow your own lemons is magical to this Canadian gal.
  11. Could be that the battery is old and leaking and is causing the corrosion. When is the last time you put a new battery in? Vehicles probably need new batteries every 5 years or so (well - in my climate they do, i.e. really cold winters). From a chemistry standpoint, car batteries are like any other rechargeable battery - the alternator recharges the battery while you drive but the recharge is never 100% so, eventually, batteries need to be replaced. Having said that, it could also be a problem with the alternator. Try replacing the battery first and see if that helps.
  12. You could use the basic outline of the one I give for Clover Valley Chemistry and modify it for other courses. Is that the kind of thing you're looking for? I can email you a copy in Word format instead of PDF if you want to be able to use the outline and modify it. 🙂
  13. Hi CCC, I responded on the High School board in case you didn't see it. 🙂 Dicentra
  14. I don't have any suggestions that I've read myself but these might be worth looking into: Introduction to Nuclear Science by Jeff Bryan The Physics of the Manhattan Project by Bruce Reed Principles of Nuclear Chemistry by Peter McPherson I think it's hard to find general interest books on nuclear chemistry/physics because it's a complicated and abstract subject - an author would need to assume a fair amount of background knowledge to be able to make the book interesting and not just another intro level textbook. 🙂 Hmmm... Digging a little more, I found this one: Superheavy: Making and Breaking the Periodic Table by Kit Chapman (but this won't be released until August 27, 2019 so she'll have to be patient :)) Actually, that one looks really interesting. I'm putting it on my own "want to read" list. 🙂
  15. Thanks, Roadrunner! To the bolded above... I outsourced English lit for my dd as soon as humanly possible. 😄 I think I've told the story before of doing poetry with her (badly) when she was young. We read through Jabberwocky because it was listed in the curriculum I was using at the time. I finished reading and my little 7 year old says, "That was nice, mummy. What does it mean?" and my response was, "I don't know, peanut. Let's do some math." 😉
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