asked in 科學及數學化學 · 1 decade ago

chem..有關...standard solution ga問題

咩standard solution

幾時會用

有咩用

點解會用?

1 Answer

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  • 1 decade ago
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    stardard solutions become handy when u need to create a calibration, or a stardard curve. the calibration and stardard curve are good to determine the concentration of the unknown from known solutions. the known solutions are then prepared by diluting the standard solutions. if u have 1 M of standard solution, and u want a well distributed graph, u would want to dilute the standard solution into 0.00M(simply a blank, such as water) 0.20 M, 0.40M, 0.60M, 0.80M and 1.00M (undiluted). with the help of spectrophotometry (or any other kinds of analytical device such as gas chromatography, liquid chromatography and flame atomic absorption spectrometry) u will be able to determine the respective reading of 0.00M, 0.20 M, 0.40M, 0.60M, 0.80M and 1.00M. with those reading, u can generate an "absorbance vs concentration" graph which u can use that to compare with your unknown absorbance. then u can figure out the concentration of the unknown.

    sometimes u need to prepare your own standard, say u are given 1.00M solution, but the range of 0.00M, 0.20 M, 0.40M, 0.60M, 0.80M and 1.00M are not suitable (too high) because the machine will reads inaccurately if the concentration is too high. then u will need to dilute the given 1.00 M into your intermediate 0.0100 M. and then u will use the 0.0100 M to further dilute into 0.0020 M, 0.0040 M, 0.0060 M, 0.0080 M and 0.0100 M.

    it is important to notice that u must accurately prepare the intermediate standard solution from the given standard. that is because the all the afterward dilution depends on the accuracy of the intermediate standard solution. if the intermediate standard solution is not prepeared accurately, your standard curve will not be accurate, hence the unknown concentration will not be correct either.

    Source(s): my analytical lab experience
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