Kemi

concentration ?

07. oktober 2009 af msn88 (Slettet)

hej

denne opgav hvilken formel skal man bruge

Exercise 1:
a) How many g of Na2S2O3, 5 H2O must be weighed in to make 5.0L approxi-mately 0.10M Na2S2O3?

The produced thiosulfate is standardized on potassium dichromate (K2Cr2O7)

Cr2O72- + 6I- 14H+ -> 2 Cr3+ + 3I2 + 7 H2O
I2 + 2 S2O32- -> 2I- + S4O62-

Triplicate determinations are done:
I: 0.1008 g K2Cr2O7 requires 18.74mL of Na2S2O3
II: 0.1033 g K2Cr2O7 requires 19.10mL of Na2S2O3
III: 0.1043 g K2Cr2O7 requires 19.42mL of Na2S2O3

b) Calculate the concentration of sodium thiosulfate in mol/L.
c) Calculate the RSD%

5.0 L = 0,50 ml = v

0,10 M = n

Na2S2O3, 5 H2O = M

m= n * M

n = m/M

c = n/ V

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