CaptainPanic

I agree, but only because you sneaked in the word "perceived". Bush did not do what's best for the USA, although he probably thought he did. It would be a welcome change if the next president does. At least, it is what we all expect. And as was said before, many of the things that are good for the US, are good for the rest of us. We're all very happy here in Europe perhaps because of a speech he gave in Berlin. In that speech he said he was aware that many Europeans feel that America is becoming part of the problem, rather than part of the solution. That one remark said a lot. Bush always thought he could bully Europe into submission or just tell us what to do. (That is how I perceive it, anyway).

Umm... we have a small molecule that does not dissolve very well in hexane. Does that still qualify it as non-polar? I also wanted to add that there are a number of "types" (lack of better word) of cobalt carbonyl. There is Co(CO)4, Co2(CO)8 and some others (not sure about this one, but if my memory is as good as I hope, then Co4(CO)12 also exists).

First of all: assuming that we're looking at energy efficiency, not comfort, it would be easier to put on a sweater if you want to be warm. Also, allowing your body to sweat and replacing that heat by for example hot tea is much more efficient than humidifying the entire house. From a theoretical point of view however, I agree that at least the human body should not lose as much heat by evaporation in moist air. However, we've discussed this before: cold wet air feels colder than cold dry air. Why? (So, if you have any ideas - because that particular thread treated a whole bunch of parameters and still had no conclusion - you know where to add that now - probably best to add it in the other thread, not this one).

I know you asked this in the chemistry forum, but I just ignore that. Use a bottle rocket! (Or water rocket). Safe, simple, cool... and really easy to reload and use again. No need to buy chemicals in a store. Totally environmentally friendly. The only disadvantage is that there's no smoke, no fire and no danger. have a read at: http://en.wikipedia.org/wiki/Water_rocket

Do you know the "Ideal gas law"? That's what I would use to calculate the density.

Eeh. At first glance the 1st reaction you posted is already balanced: [ce]SeF4 + 4(CH3)3SiCN -> Se(CN)4 + 4(CH3)3SiF[/ce] But you want to look at another reaction: [ce]SeF4 + 4(CH3)3SiCN -> SeC2N2 + 4(CH3)3SiF + X[/ce] [ce]X[/ce] is the unknown compound. You need to look at the difference between the compounds. Count all the elements on the left side (how many of each element) and also on the right. They should be the same (like in the 1st reaction). If they are not, then you know what to put in the compound [ce]X[/ce].

(by now it's been a week since this thread was opened) lol Newbie joins the forum, and his only contribution is a question where he must post the thread with his yet unasked question? He's a born bureaucrat

Thanks! It is great to see that girls also understand something about cars. However, if you would have read anything other than just the thread title, you might have replied with something different

The presence of magnetic field lines (as written in the article) fascinates me. If there are magnetic field lines connecting the sun and earth, then the orbit of earth is not caused by gravity alone. There must be a magnetic force as well. And I agree with previous two posts that "portal" is a misleading name. Portal suggests some kind of instant transfer.

Temperature is the only factor that causes condensation. Close to a cold surface, the air is also cold. This means that the partial vapor pressure of water is lower. That means in turn that the air becomes saturated and even supersaturated with water. So it condenses. The heat capacity (or specific heat, units J/kgK) only means that an object remains cold longer. But if you take 2 objects with identical outer surface area: one colder than the other, but having a lower heat capacity than the other, then the colder object will have a larger initial condensation rate (expressed in mass/time (condensation per time). As it heats up, the condensation will be reduced (the object heats up, vapor pressure increases, supersaturation decreases, condensation reduces). That is a possible reason to humidify the house. Energy savings is not. You might want to try a cream against dry skin. Whether that helps, I don't know (I don't use such creams myself).Anyway, people in my country don't need humidifiers. We live in a swamp that we drained and now call the Netherlands. That is correct. I merely wanted to indicate that additional to the radiation, a mass flow of water vapor introduces a new heat flow. Apologies for hijacking this thread. I think that the topic is important enough though.

I thank all Americans for doing the right thing: voting for Barack Obama. Let's hope he lives up to the promise, although I think that the positive feeling that the world got today is already invaluable.

Looking first at only [ce]H2[/ce]: I'm assuming that temperature doesn't change. If you want, you can assume any temperature and use the ideal gas law. That works too. Before opening stoplock: [math]P_1(H_2)\cdot{V_1(H_2)}=n(H_2)\cdot{R\cdot{T}}[/math] After opening stoplock: [math]P_2(H_2)\cdot{V_2(H_2)}=n(H_2)\cdot{R\cdot{T}}[/math] Obviously, n does not change (you have no reactions, and you cannot create new molecules from nothing). T was assumed constant. Therefore: [math]P_1(H_2)\cdot{V_1(H_2)}=n\cdot{R\cdot{T}}=P_2(H_2)\cdot{V_2(H_2)}[/math] Or: [math]P_1(H_2)\cdot{V_1(H_2)}=P_2(H_2)\cdot{V_2(H_2)}[/math] Or: [math]P\cdot{V} = constant[/math] Same equations are used for [ce]N2[/ce]. Then you add up the partial pressures [math]P_2(H_2)+P_2(N_2)=P_2(total)[/math]. The point that got me puzzled now is that mixing the gases will have an entropy effect. Furthermore, one side will have expansion, the other compression. The question asked doesn't seem to indicate that these factors should be included...

Yes, I was assuming we're talking about winter. And yes, you're only moving energy around if you evaporate and condense again. But: you've moved energy to the cold part of the house. Why is that part of the house cold? Because it is a spot that has a good heat transfer to outside. Therefore, if you increase heat transfer to a spot that is itself also good at heat transfer to outside, you've effectively increased the heat transfer from the hot place (dish washer) to outside. I don't see the point of moisturizing the house. To evaporate the water you'll still be spending the same energy, whether you evaporate it from the dishwasher or from a dedicated device. And, if there are any parts in your house are cold, the water will condense there. Just to make the heat balance picture complete: The other heat effect is radiation (mostly infrared radiation) which originates from any object. Warmer objects lose heat through IR radiation. But it radiates in a random direction (which is better than targeting the coldest part of the house). But it is also true that allowing hot water to leave the house through a drain is another waste. (People generally don't realize that opening a hot water tap is equivalent to turning on a 10 kW machine. Of course that depends on the water flow (liters/second) and temperature of the water - and efficiency of heating).

I'd say that the fuel consumption will be the greater problem at such speeds. We're talking about cars, not trains... they each have their own front end, which means they each will be attempting to break through the air (greater air resistance than a single train carrying 500 people). I think the best argument for automated systems is not accident prevention. It is that cars can drive closer to each other (possibly because they can communicate with each other). This can greatly increase the capacity of a road... and in turn greatly decrease traffic jams.

It might tell you something about the Gibbs energy of reaction. But if you don't know what that means, then it's not the answer your teacher is looking for... If you do know what it means, then you can also answer the question.

Gases that mix don't change temperature (unlike liquids, that can have a significant temperature change when you mix). So, the temperature is irrelevant. Step 1. Convert everything to normal SI units (Pascal for pressure). The volume is preferred in m3 (cubic meters). Step 2. Realize that if you have 1 bar pressure in 1 m3, and you expand that to 2m3, the pressure will be 0.5 bar. P*V = constant in this case. Step 3. Realize that partial pressures can be added up to forms the total pressure. If, in the same volume, you have 0.5 bar of gas A, and 0.6 bar of gas B, the total will be 1.1 bar of gas A+B. Step 4. Convert your answer back into the units (torr, atm, psi, whatever) asked by the teacher.

I disagree with this. I'll treat three examples separately: oven, dishwasher and dryer. Oven The heat contained in the oven must go somewhere in order to cool the oven. There are only 2 ways to cool down the oven after you made a pizza: either you heat up the house (heat is lost into the inside of the house) or you directly heat up the outside air or ground. Since most ovens are well insulated, I agree that neither should go really fast with the door closed. But: keeping the door closed does certainly not mean that you automatically lose all heat to the outside air. Especially electric ovens are not in contact with the outside air, so it really does not matter whether you open or close the door. Every joule of energy has to travel through your house to the outside air. It does not really matter if you open or close the oven, unless you have an open fire oven and a chimney (in that case, some heat will disappear through the chimney). But that's really old fashioned technology. Dishwasher The dishwasher is hot and wet on the inside. If you open it, water will evaporate to cool it down. (Almost all excess heat is put into evaporating water). That energy is returned to your household in the form of heat when the water condenses again. A lot of the water will never condense (assuming you don't live in the Netherlands, where air humidity actually is 100% half the year, and it will condense). So, that energy is lost. It will leave your house through whatever form of ventilation you have. And even if it did condense, it typically condenses on the coldest part of your house. Those are, in general, the parts in direct contact with the cold outside. If you condense water on those surfaces, you're basically heating up the outside air. I have to say that I'm not sure how you're supposed to dry your kitchen stuff if you don't open the dishwasher. But it's bad for the energy bill. Dryer Because normal hot air dryers (not the condense dryers) have their own ventilation, it might be a good idea to open the door. I wonder however how much air is lost. My dryer has a total negligible air flow to outside when it's done, so it makes no difference. Condense dryers, like an oven, are not in direct contact with the outside, so it makes no difference whatsoever. Conclusion For ovens and dryers it doesn't make much of a difference whether you open the door or leave it closed. For your washing machine or any other application that is wet on the inside, it is bad for your energy bill to open the door.

It's one thing to replace all cars (they're made of steel, and that's fairly easy to recycle). To replace the roads as well would be a different thing altogether. You can replace the highways and popular secondary roads with rail systems, or place overhead whatevers. But it's not economical to replace even the dirt roads and forest paths... and think about the complexity of a large parking area? A large slab of asphalt or concrete is just so much cheaper. To reduce the fatalities on the road, I think that some form of object detection is needed. These are being developed at the moment. It just detects any object that has the potential to hit the car (that can include a deer running onto the road). These systems are just that 0.5 second faster than the human driver. But you cannot reduce the risk to zero simply with such a system. And a fence along every road is also no option. Replacing the driver completely with any GPS or other navigation system is overdoing it. How many fatalities are caused by people who are lost? Compare that to the number of computer bugs you've seen in your life. I'd rather navigate (steer the car) myself Concluding: I don't see the point of replacing the driver completely. But drivers can use a little help in dodging objects that suddenly appear on the road.

I like the comparison with Sweden, where McCain says that "in the Swedish system it doesn't pay to work more than 6 months a year". He did not reach any conclusion, he just assumed that people agree that it's a bad thing. That was a bad argument, because Sweden happens to be one of the wealthiest countries in the world. So, we must conclude that apparently the Swedish get something in return for their high tax rates. It is not wasted. I'm not sure (I don't live there), but I bet that education is much cheaper there, they have healthcare for free and lots more things. A socialist government does more for its people... it's not necessarily bad... and I don't understand why people don't see that. If you pay more tax, you get more in return (unless your government is known to spend more in "defense" (warfare) than all the rest of the world together).

That kinda depends - are you supposed to do it in the lab, or make a reasoning on paper?

In many countries the comma is used for decimals, and the dot is used at the thousand, million, billion positions... There are actually two systems. It's totally retarded that this exists, and it's utterly stupid (typical Microsoft) that if you have for example a Dutch computer and Excel refuses to make decimals if you push the . on the keypad. But it's only wrong in English speaking countries (and perhaps some more that I am not aware of). Chemistry rules!

I'm not sure how to answer this because I have not often encountered a number for polarity. Which units does polarity have, accoring to you? I've heard (merely a rumor) that there is some kind of UV-shift scale where a chemical compound changes color depending on the polarity of the solvent in which it's dissolved. Iodine is an example, it changes color depending on the polarity of the solvent in which you dissolve it. but whether you can use that for determining the polarity of arginine, I don't know. Arginine is not a solvent (it's not even a liquid when it's pure). Another scale (again a rumor) is simply a comparison between two compounds: one is, I believe hexane, the other I forgot. I called all these rumors because I failed to find any info to back up my claims here. But perhaps this helps others to add some real facts here p.s. the polarity of arginine changes with pH: at certain pH values it is positively or negatively charged. And I wouldn't be surprised if some funny stuff happens with the electron positions as a function of pH in the neutral range (zwitterion). Therefore I doubt that you can find 1 single number for the polarity of Arginine.

Good question. I'd go for Engineering or perhaps Experiments ,Equipment or Projects. If you put it in the "wrong" place, a moderator might move it. That's no problem, especially for new people. So, just post the question, and make sure to be as clear as possible. A good question (with explanation what you already know, and perhaps why you need it) is more important than finding the right place.

A mole is a number. It's just a funny name for a very big number. I like to compare it to a dozen (12) and a gross (12x12 = 144). In the same way, a mole is 6.022*10^23 (note that the number in the opening post is not avogadro's number - there is an error there). the question you need to solve here is similar as the question: You have 27 apples, how many dozen of apples do you have? A dozen is 12. You have 27/12 = 2.25 dozen.

If a balloon, like in the example I gave above, weighs the same as the air it contains, that will also be the case if it gets compressed... The air gets compressed, and the plastic shrinks. But indeed, on top of Mt. Everest, the balloons will contain much less air than they weigh themselves... because they would pop if they did... and my whole idea does not hold. (Therefore, it will also not be possible to let up a helium balloon on top of Mt. Everest - not a normal standard party balloon anyway - weather balloons obviously have no problem.)