Banaticus
Sep26-06, 01:05 PM
How many Cr atoms in 78.82 g potassium dichromate?
Potassium dichromate is \textrm{K}_{2}\textrm{Cr}_{2}\textrm{O}_{7}.
I said:
The molecular mass of potassium dichromate is:
39.1*2+52*2+16*7=294.2
So, in 78.82 g potassium dichromate, there are 78.82/294.2= 0.2680 moles of potassium dichromate. Each mole of potassium dichromate has 6.022~x~10^{23} molecules, each with 2 chromium atoms. So, in one mole, there are 1.204~×~10^{24} chromium atoms. So, in .2680 moles, there are .2680(1.2044~×~10^{24})~=~3.228~×~10^{23}, correct?
As a sidenote, it appears that LaTeX graphical formulas can't be seen in the preview mode -- the only way to check them is to post the message then edit the message if they're wrong? Also, where can I find a better LaTeX tutorial than http://www.physicsforums.com/misc/howtolatex.pdf which just doesn't give enough information? Ah, http://www.physicsforums.com/showthread.php?t=9021 has some pretty good information, but I still don't seem to be doing my LaTeX correctly.
Potassium dichromate is \textrm{K}_{2}\textrm{Cr}_{2}\textrm{O}_{7}.
I said:
The molecular mass of potassium dichromate is:
39.1*2+52*2+16*7=294.2
So, in 78.82 g potassium dichromate, there are 78.82/294.2= 0.2680 moles of potassium dichromate. Each mole of potassium dichromate has 6.022~x~10^{23} molecules, each with 2 chromium atoms. So, in one mole, there are 1.204~×~10^{24} chromium atoms. So, in .2680 moles, there are .2680(1.2044~×~10^{24})~=~3.228~×~10^{23}, correct?
As a sidenote, it appears that LaTeX graphical formulas can't be seen in the preview mode -- the only way to check them is to post the message then edit the message if they're wrong? Also, where can I find a better LaTeX tutorial than http://www.physicsforums.com/misc/howtolatex.pdf which just doesn't give enough information? Ah, http://www.physicsforums.com/showthread.php?t=9021 has some pretty good information, but I still don't seem to be doing my LaTeX correctly.