Can't Judge A Powder B

dholdgreve
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Re: Can't Judge A Powder B

Post by dholdgreve »

hmssciencenerd wrote:Should i memorize the periodic table :geek:
Your time would be better spent studying a glossary of chemical terms, types of chemical bonds, What elements react with NaOH to form insoluble salts (and why), What chemicals react with HCl and what that reaction might be? How you would know if Ammonium ions were present in the sample? Nail all that and you'll be a super star!
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Re: Can't Judge A Powder B

Post by Gearbox »

What is the best way to keep track of the observations you come up with? Thanks :D
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Re: Can't Judge A Powder B

Post by Gearbox »

Katkatkat wrote:Can someone please tell me the strength of the sodiumhydroxide solution? I found a local store, but I need to know the percentage.
It is most likely .1 molar or 1 molar, there really isn't much of a percentage, I guess you could say that .1 molar is 10% but its better to say that one liter of the solution contains .1 moles of NaOH
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Re: Can't Judge A Powder B

Post by sandhya_326 »

How do you measure the conductivity of powder in 1M HCl and 1M NaOH because conductivity of HCl and NaOH itself is very high. I just bought a cheap conductivity meter Hydroponics Aquarium EC Conductivity Tester Meter µS/cm from Amazon for coaching kids. Does it work? Or any other suggestion for measuring conductivity in HCl and NaOH. Thx
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Re: Can't Judge A Powder B

Post by dholdgreve »

sandhya_326 wrote:How do you measure the conductivity of powder in 1M HCl and 1M NaOH because conductivity of HCl and NaOH itself is very high. I just bought a cheap conductivity meter Hydroponics Aquarium EC Conductivity Tester Meter µS/cm from Amazon for coaching kids. Does it work? Or any other suggestion for measuring conductivity in HCl and NaOH. Thx
I believe the ionization of a chemical relates primarily to the free ions released in distilled water, with the quantitative portion being the delta between the distilled water and the aqueous solution... To receive full credit for a questions dealing with electrolytes, conductivity of the substance, ionic bonding, etc, observations need to be included that include conductivity of the distilled water itself (control observation), approximate amount of substance added to approximate amount of distilled water (it doesn't matter how much, the important thing is that it is quantified), and the conductivity of the resultant aqueous solution.
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Re: Can't Judge A Powder B

Post by chem_mom »

Has anyone tried putting together a conductivity tester using the instructions given on the CAJP wiki site? Is it necessary to solder the wires? Are the ready made testers working well? Thanks!!
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Re: Can't Judge A Powder B

Post by robotman »

The conductivity tester described in the wiki does indeed work. Soldering the connections is suggested, as it will make the connections more durable and precise, however not required. The main benefit for the one described in the wiki is it is fairly cheap to make, and easy to get done in a pinch.

Commercial Conductivity testers work great as well, this is the one I have seen used most often in CJAP. Flinn Conductivity Tester
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Re: Can't Judge A Powder B

Post by Skink »

My team assembled and tested one the other day. I recall commenting that it didn't look so great, but it works beautifully! They did note that they bought the best LED they could find, which may have an impact on performance. I would be interested in hearing if it does or not.
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Re: Can't Judge A Powder B

Post by chem_mom »

robotman wrote:The conductivity tester described in the wiki does indeed work. Soldering the connections is suggested, as it will make the connections more durable and precise, however not required. The main benefit for the one described in the wiki is it is fairly cheap to make, and easy to get done in a pinch.

Commercial Conductivity testers work great as well, this is the one I have seen used most often in CJAP. Flinn Conductivity Tester
Thanks for the reply. We made our tester and it worked!! We twisted the wires round each other and used alligator clips for better connection. It sometimes falls apart so we will make some adjustments.
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Re: Can't Judge A Powder B

Post by knittingfrenzy18 »

Just some suggestions for you all that are building your conductivity testers:

I went to the craft store and picked up a little wooden box with a hinged lid and a latch, and drilled some holes in the top and side. I taped the battery to the inside of the box, and glued the LED to a hole in the top (which let the leads through) and all the messy resistor + wiring and stuff is contained inside the box. Some longer wires protrude out the side of the box, and voila, a very concise, neat box with a switch (I decided to include one for safety measures to protect the LED), an LED, and some wires. :)
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