Qualification > Sciences
Edexcel CHEMISTRY DOUBTS!!!!
Summer :]:
--- Quote from: Psyclax on May 12, 2010, 12:52:54 pm ---How do we calculate the solubility of a substance???
--- End quote ---
grams dissolved in the water
its just the basic equation of moles that you should use
no of moles = mass/ Mr
find the mass..thats all..
Summer :]:
--- Quote from: Tammy on May 12, 2010, 12:02:58 pm ---i have a question about percentage error.....
The balance used to weigh the magnesium carbonate is accurate to +-0.01 g. Calculate the percentage error in the mass of the magnesium carbonate weighed. ((weighed MgCO3: 0.21g))
the correct answer is 0.02
-----
0.21
Why is it 0.02 not 0.01?? and when do we write it as 0.01??
Thanks in advance peeps
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because
it says +- 0.01
therefore the range could be 0.21 - 0.01
and 0.21 + 0.01
so add those values together 0.01 + 0.01 = 0.02
its always this way i guess..thats what my teacher told us *shrugs* ::)
ksitna:
--- Quote from: luluabdl on May 12, 2010, 04:34:14 pm ---So in Acid-Base equilibrium when were trying to find the pH of a buffer solution, is the rule:
pH = pKa + log([A – ] ÷ [HA])
OR
pH = pKa - log([A – ] ÷ [HA])
Because in the book they're using the one with the -log and in some questions in the pastpapers they're using the +log. Which one is it exactly?
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we have to use log in AS chemistry???
luluabdl:
--- Quote from: ksitna on May 12, 2010, 04:40:35 pm ---
we have to use log in AS chemistry???
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Sorry wrong post, this is A2 :)
ksitna:
--- Quote from: luluabdl on May 12, 2010, 04:43:21 pm ---Sorry wrong post, this is A2 :)
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ohh okie
jeez man u freaked me out!!!!
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