Can't Judge a Powder B

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Re: Can't Judge a Powder B

Post by haven chuck »

melody2k6 wrote:We don't have the test packet.
This wasn't on the test this year, but here is what they wanted in '06-
Put a set amount of the powder in a beaker and weigh it. Leave it alone for at least 15 minutes and then weigh it again. If there is a change is weight, then it is likely hygroscopic; if not, then it isn't. However, this process can take a fair amount of time if you have a shared triple beam balance (when you have so little time to start with), so it is probably worth considering just writing down something to the effect of "The powder clumps". This simple would receive AT LEAST 3-4 points anywhere, though most Invitational/Regional/State supervisors would probably give it 5, and would take far less time.
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Re: Can't Judge a Powder B

Post by ichaelm »

Hmm. We just did clumping as an observation, and then we would test to see if it was hydrophobic by seeing if water made it wet when a drop was put on it. We would write "the powder does/does not adsorb to water." Note that "adsorb" is not a typo! :D
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Re: Can't Judge a Powder B

Post by 2win »

melody2k6 wrote:
r00ki316 wrote:Please tell me I don't have to police you on the boards, Brian.
I think there's a rule against using real names on Scioly. Give Brian a break! Meanwhile, you should realize that it's very coincidental that Solon asked a question about hygroscopic-ness...
Um, not to be mean or anything, but please refrain from posting non-related comments on study/building threads. You could always use PM's.
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Re: Can't Judge a Powder B

Post by melody2k6 »

2win wrote:
melody2k6 wrote:
r00ki316 wrote:Please tell me I don't have to police you on the boards, Brian.
I think there's a rule against using real names on Scioly. Give Brian a break! Meanwhile, you should realize that it's very coincidental that Solon asked a question about hygroscopic-ness...
Um, not to be mean or anything, but please refrain from posting non-related comments on study/building threads. You could always use PM's.
Sorry. I have terrible judgement of simple things like that. Did anyone understand the question about the rotten egg odor? My partner and I had no idea what it meant.
Last edited by melody2k6 on May 29th, 2010, 9:45 pm, edited 1 time in total.
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Re: Can't Judge a Powder B

Post by robotman »

melody2k6 wrote:

Sorry. Did anyone understand the question about the rotten egg odor? My partner and I had no idea what it meant.
I think My partner and I did.
It was the Feric something (brownish color) that had the rotten egg odor
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Re: Can't Judge a Powder B

Post by melody2k6 »

robotman09 wrote:
melody2k6 wrote:

Sorry. Did anyone understand the question about the rotten egg odor? My partner and I had no idea what it meant.
I think My partner and I did.
It was the Feric something (brownish color) that had the rotten egg odor
Did it ask for something else though? I thought the question asked something about another observation we can make about Ferric Nitrate (I think. Not sure though)
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Re: Can't Judge a Powder B

Post by frogzorz »

Hmm. My partner and I concluded that it was the sodium sulfide. After all, sodium sulfide (Na2S) contains 2 molecules of sulfur, even in its hydrate form. Both the compound and its hydrate emit hydrogen sulfide, which smells like rotten eggs.
BTW, what the heck is ferric acid? The reactioms to it were similar to HCl except for a few.
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Re: Can't Judge a Powder B

Post by starpug »

frogzorz wrote:Hmm. My partner and I concluded that it was the sodium sulfide. After all, sodium sulfide (Na2S) contains 2 molecules of sulfur, even in its hydrate form. Both the compound and its hydrate emit hydrogen sulfide, which smells like rotten eggs.
BTW, what the heck is ferric acid? The reactioms to it were similar to HCl except for a few.
How does Sodium Sulfide have 2 molecules of sulfur when the charge on sulfur anion is -2 and the charge on the sodium cation is +1.
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Re: Can't Judge a Powder B

Post by rocketman1555 »

frogzorz wrote:Hmm. My partner and I concluded that it was the sodium sulfide. After all, sodium sulfide (Na2S) contains 2 molecules of sulfur, even in its hydrate form. Both the compound and its hydrate emit hydrogen sulfide, which smells like rotten eggs.
BTW, what the heck is ferric acid? The reactioms to it were similar to HCl except for a few.
Sodium sulfide only has one molecule of sulfur, it has two molecules of sodium though.

And Ferric Acid is a weak acid, I don't know much else about it though.
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Re: Can't Judge a Powder B

Post by frogzorz »

Oops. My bad. I thought it had two sulfur molecules. I hate my partner!! :evil:
A weak acid? We tested for a pH of 1 or 2.
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