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July 15, 2025, 06:58:51 am
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Water

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Chemistry Question
« on: January 03, 2011, 03:14:38 pm »
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Phosphate rock, used in the manufacture of fertilisers, is a mineral containing phosphate,hydroxide and calcium ions. To determine the calcium content of an impure sample of rock phsphate, a 0.442g sample was dissolved in water. The calcium ions presentw ere precipitated as hydrated calcium oxalate (caC2O4.H2O) . The mass of precipitate obtained was 0.298g. Calcium the percentage by mass of calcium in the rock phosphate.

hey guys, I got an answer of 18.5% based on my calculations. i don't have the text book answer, but I just wanted to make sure if the answer was correct. Based on my peers :)
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When I see a youth thus engaged,—the study appears to me to be in character, and becoming a man of liberal education, and him who neglects philosophy I regard as an inferior man, who will never aspire to anything great or noble. But if I see him continuing the study in later life, and not leaving off, I should like to beat him - Callicle

John President

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Re: Chemistry Question
« Reply #1 on: January 03, 2011, 04:48:30 pm »
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That's what I got as well.

Fairly typical stoichiometry question - I guess a common trap would be leave out the H2O when calculating the molar mass, because I almost forgot it  :-[

But with your name being "Water" I doubt you'd make such a mistake - it'd be truly ironic if you had.
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Water

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Re: Chemistry Question
« Reply #2 on: January 03, 2011, 08:41:28 pm »
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Thanks a bunch :) , phew* xD
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About Philosophy

When I see a youth thus engaged,—the study appears to me to be in character, and becoming a man of liberal education, and him who neglects philosophy I regard as an inferior man, who will never aspire to anything great or noble. But if I see him continuing the study in later life, and not leaving off, I should like to beat him - Callicle

Water

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Re: Chemistry Question
« Reply #3 on: January 04, 2011, 12:49:46 pm »
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I got another Chem Question, Stoic, sorry guys, haha, i don't have the textbook answers so I feel really insecure xD... Hope you guys can bear with me :)


A sample of hydrated copper (II) sulfate  (CuSo4.5H2O) is contaminated with silica. A 13.86g sample of the compound was dissolved in water and filtered to remove the insoluble silica. An excess of barium chloride solution was added to the filtrate, and the resulting precipitate collected and dried. If the sample contained 5.05 g of silica, what mass of barium sulfate precipitate would be expected?

So basically I did the m(sample) - m (silica) = m(CuSo4)
Which would be 13.86g - 5.05g = 8.81g

and then I used that m(cuSo4) and did my mol etc..etc..


My final answer was m(BaSO4) = 12.8g


Not sure if its right ^^..Hope I can get it confirmed tih someone
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About Philosophy

When I see a youth thus engaged,—the study appears to me to be in character, and becoming a man of liberal education, and him who neglects philosophy I regard as an inferior man, who will never aspire to anything great or noble. But if I see him continuing the study in later life, and not leaving off, I should like to beat him - Callicle

Russ

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Re: Chemistry Question
« Reply #4 on: January 04, 2011, 01:09:11 pm »
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I don't have a calculator on me, but did you take into account the water when you were calculating this (because you left it out of your working)
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Water

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Re: Chemistry Question
« Reply #5 on: January 04, 2011, 01:14:50 pm »
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Correct, I did re calculator, by adding the 5H2O, and etc.... , my final answer for BaSo4 was 8.21g, I think its right. It looks right xD
« Last Edit: January 04, 2011, 03:33:40 pm by Water »
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About Philosophy

When I see a youth thus engaged,—the study appears to me to be in character, and becoming a man of liberal education, and him who neglects philosophy I regard as an inferior man, who will never aspire to anything great or noble. But if I see him continuing the study in later life, and not leaving off, I should like to beat him - Callicle
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