_ The quantity of antimony in a sample can be determined by an oxidation-reducti
ID: 969213 • Letter: #
Question
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The quantity of antimony in a sample can be determined by an oxidation-reduction titration with an oxidizing agent. A 9.33-g sample of stibnite, an ore of antimony, is dissolved in hot, concentrated HCl(aq) and passed over a reducing agent so that all the antimony is in the form Sb3 (aq). The Sb3 (aq) is completely oxidized by 48.1 mL of a 0.110 M aqueous solution of KBrO3(aq). The unbalanced equation for the reaction is BrO-3 + Sb3+ ----> Br- + Sb5+. Calculate the amount of antimony in the sample and its percentage in the ore.
______ grams
_______%
Explanation / Answer
balanced equation
BrO3^- + 6H^+ + 3Sb^3+ ---> Br^- + 3Sb^5+ + 3H2O
from equation
1 mol BrO3^- = 3 mol Sb^3+
No of mol of BrO3^- reacted = 48.1/1000*0.11 = 0.00529 mol
No of mol of sB^3+ present in sample = 0.00529*3 = 0.01587 mol
mass of Sb^3+ = 0.01587*121.76 = 1.932 grams
percentage of Sb = 1.932/9.33*100 = 20.7%
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