<p>Please forgive me, I've just started AP chem and within the course of about 2 weeks we've gotten a new teacher and I haven't learned a thing!!! UGh i'm soo stressed out.. OKay mY question deals with conversions and density. First How do u go from mn (I can't do it right.. its like a squigly m) to nm, and from s to ms.. and if possible do I need to memorize these conversions for the AP exam.. And now density. I understand that density= mass/volume but this is if you're assuming that the temperature is 25 C. So how do I figure out density (or mass or volume) if the temperature changed to like.. 15C? It does affect it right? Again I'm sorry if this sounds pretty elementary, I'm just a lil lost. Thank you!!!</p>
<p>BTW if you know anything bout the AP Chem exam thats INCREDIBLY USEFUL, in terms of understanding the material or anything else.. I'd be sooOOOoOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO grateful :)</p>
<p>Uh for your density question recall the ideal gas law
PV = NRT
N = number of moles or also known as grams/total grams.
So what you want to do is re-write the question
PV = mRT/M
m = mass u r given for density. Big M = GMM (gram molec. mass).
re-write it again and write it out to be just m/V on one side. You get
.. PM/RT = m/v
So If PM/rt = density and R is a constant as well as M, you only have to worry about P and T. In the problem you are doing are they saying the pressure stays the same? If so then this is what you do.
Oh and don't worry. density, if at all, is seldomly on the test.</p>
<p>ms is milliseconds I assume? Milli is the prefix for one thousandth, or 10^-3. Knowing that, I hope you can convert s to ms.</p>
<p>They dont have anything baout ms or mili seconds. They do have like KG or the common pressure units but nothing too hard. Study PPM (parts per million) because that was on the test before i heard.. i dont think anything like ms to s is though.</p>
<p>nm = nanometers 1 nanometer = 10^-9 m
density = mass/volume
PV=nRT
V = volume
n (# of moles)= mass/molecular weight
I just derive it from pv=nrt anytime i need to use it..so just substitute in N= mass/molecular weight and solve for mass/volume</p>