Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: noiseordinance on April 11, 2009, 08:51:49 PM
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This term is really making a chump out of me, lol. Here's another question... I don't think I understand it but I bet one of you will...
How many total moles of ions are released when the following samples are dissolved in water?
0.805 mol Rb2SO4
So, I started by writing out the balanced equation, 1 Rb2SO4 + 1 H2O ---> 1 Rb2O + 1 H2SO4
Am I just supposed to figure out how many moles of Rb2O and H2SO4 are produced from the 0.805 mol Rb2SO4?
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dissolved in water?
The reaction, you wrote, :
1 Rb2SO4 + 1 H2O ---> 1 Rb2O + 1 H2SO4
Does not describe what happens when you dissolve a solid in water. Let's try a less esoteric one, so we can cover the basics. When you dissolve 1 mole of NaCl in water, how many moles of ions do you get? Check your textbook's index for "dissolve" and "ions", you may find what you've missed.
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You're right, I missed something. Apparently, when dissolved the ions separate and do not bond with the hydrogen and oxygen in the water. So maybe this is more accurate:
1 Rb2SO4 ----> 2 Rb + 1 SO4
So, 1 mole of Rb2SO4 molecule becomes 3 moles of ions, so it's a 1:3 ratio right? If that's true, would I be accurate to write it as such:
0.805 mol 1 Rb2SO4 (3 mol ions / 1 mole 1 Rb2SO4) = 2.42 mol ions
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Very good. I like that you're using dimensional analysis, to keep track of units. It would be better, later on, if when you write an ionization reaction like this, that you don't neglect to add the charges to the ions.
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Right right, I usually write them on the paper but I sorta get a little lazy with the sup / sub buttons. :)
Thanks a lot! I appreciate the help. I changed campuses and I have the chemistry book from my last campus that I just spent $150 on and my new teacher is nice enough to scan the questions out of the suggested textbook so I can keep using my personal textbook without having to buy a new one, yet, as a consequence, I can't check my work on these practice problems... d'oh! Thanks again!
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Right right, I usually write them on the paper but I sorta get a little lazy with the sup / sub buttons.
At least write them using - and +. To avoid (part of the) confusion you may use notation like SO4-2.