hermanntrude

i didn't follow your reasoning about the "crisscross" and the molecular and empirical formula (this is an ionic compound so it doesn't have a molecular formula, because there are no molecules). The only way to reason it out is that the (IV) means the Mn is Mn4+ and you should know oxygen is almost always O2- in ionic substances, so to balance the charges you must have 2 oxides for every manganese.

what I think you mean is that because the effusion time was longer, the mass of the unknown gas should be greater than that of oxygen. Perhaps I didn't explain grahame's law very well. In this case it looks like this, but bear in mind the ratio of molar masses might be the other way up for some of the listed properties above: [math]\frac{{effusion time O_{2}}}{{effusion time unknown gas}}[/math]=[math]\sqrt{\frac{M_{O_{2}}}{M_{unknown}}}[/math] I think that's how it works, anyway. I got myself a bit confused with the Latex stuff and now i've lost track of my thoughts

check the formula for manganese (IV) oxide. Remember the (IV) states the charge on the Mn ion, not the number of oxides.

thanks man!

I can't really check your answer without a balanced equation. I'm not too sure of the reaction here. However, the steps should go like this: 1: calculate the mass of HCl produced assuming manganese chloride is LR 2: calculate mass of HCl produced assuming chlorine is LR 3: calculate mass of HCl produced assuming water is LR 4: choose the smallest number each of steps 1-3 can be in turn broken into smaller steps: a) calculate number of moles of reactant by dividing mass by molar mass b) calculate number of moles of product (HCl) by using a stoichiometric conversion factor c) calculate mass of HCl by multiplying by molar mass

OK question 1 required Grahame's law, which can be written like this: a ratio of any of the following properties for a pair of gases is equal to the square root of the ratio of their molar masses: molecular speeds effusion rates effusion times distances travelled by molecules amounts of gases effused the best way to use this law is to reason it out quantitatively first, ask yourself "should the ratio be greater or less than one?" In this particular question, that can be rephrased as "would you expect the unknown gas to have a higher or lower molecular weight than oxygen based on the fact it effused more slowly?" then use the ratio of molar masses whichever way up works for your reasoning. then just use the times and molecular weights to make an equation, plug in the numbers and solve for the molecular weight of the unknown.

lol no problem! My students have their final exam tomorrow and I wish at least one of them cared half as much as you seem to.

1234.5 is Pfinal x Vfinal. Divide by the volume of the final system

<points to the "did you like this post" link> :0)

yuck. I've seen questions like this before with two bulbs but not three. nasty question. however, what you need is a modified version of boyle's law (notice the numbers of moles and the temperature is constant. that should always scream "boyle" to you). basically the sum of the products of the pressures and volumes in the three separate flasks should equal the product of the pressure and volume of the single container after the stopcocks are opened: [math](P_{1}V_{1})+(P_{2}V_{2})+(P_{3}V_{3}) = P_{final}V_{final}[/math] where the subscipts 1,2 and 3 represent the values for the three flasks. Merged post follows: Consecutive posts merged the stopcocks are between the flasks, i suspect. Also there's no such thing as a negative pressure. if the flasks were opened to the atmosphere, the final pressure would be atmospheric pressure.

OK, i'll tell you what I did, because it cleared it up a bit. I drew three flasks and labelled them. The first flask was 5L, 2gSO2 and 18°C, the second flask was 2.5L, 3.5g N2 ans 20°C. the third flask I only labelled the volume (10L) and the temperature (25°C). After that it was a bit clearer. Each of the original flasks contains the information required to find the numbers of moles of the gases, SO2 and N2. Once you've done that you can find the numbers of moles of N2 and SO2 and the total number of moles. After that you can find the total pressure in the flask, using the ideal gas law. Then you know everything you need to know: the mole fraction of SO2 and the total pressure.

the formula you're looking for is under "kinetic molecular theory of gases" in your textbook. it's something to do with the rms speed being equal to the square root of (3 times the gas constant times the temperature divided by M)... I think... something like that... look it up.

yes we can't login to YOUR homework site. Plus it's generally useful if you can give us a general gist of your thoughts on the matter before asking us. Also try to think of this website as a learning tool rather than a magic answer-generator. Good luck in your final.

I expect it can, although it'd be hard work. I still don't understand why you want to spend the time purifying potassium nitrate when you could just go out and buy it

why would you want to do that?

thanks for the info, but i suspect this add-in is a little redundant... I use MSword for writing chemical worksheets and tests and exams regularly. I have autocorrect set up to change "-->" into an arrow, and "delta" into a delta symbol, I have a special font for special symbols like arrows with catalysts on them and so on, and I generally find shift works quite well for capitals. Also Ctrl and + toggles subscript and ctrl, shift and + toggles superscript.

nom nom nom nom 0000000

melting point is usually a good indicator of purity. potassium chlorate decomposes very shortly after melting so don't be surprised to see a lot of oxygen bubbles coming off. You could also try this: http://www.springerlink.com/content/p10q88m65t3p6644/ Although that's only specific for chlorate, so it wouldn't indicate, for instance, if you had sodium chlorate present.

look up "eutrophication"

lol that's rather hard to answer. There are millions of chemists in the world and we don't know where you're expecting yours to do their work, plus we still really don't know what the application is for your detection setup. Now if you want a guy to do simple chemistry in newfoundland at about 30 minutes a day and you're paying about $10,000 a week, then I'd reckon I know a man who can help.

yes, but did the news report have to be a current news report?

The trouble with that is that urea exists in all sorts of places, and of course not only in human urine...

two things which may be informative for you to look up are organophosphates and DDT. try wikipedia. They both had dangerous consequences

i imagine that'd be hard thing to do. urine contains a mixture of compounds, most of which occur in nature elsewhere. It all depends on what quantity of urine you need to be able to detect in that half-gallon and what other impurities are likely to be present... what is the source of the freshwater?

remember that hess's law states that any process that occurs in steps, even if the steps are hypothetical, has the same enthalpy as the non stepwise process. can you draw an enthalpy level diagram which connects up the cis and the trans isomers through a known route that you CAN look up?