Question

ProblemWhat is the concentration of a tin(ll) chloride solution prepared from a sample of tin ore?Experimental DesignThe potassium dichromate solution is first standardized by titration with 15.00 mL of an acidified 0.07 mol/L solution of the primary standard, iron(II) ammonium sulfate-6-water. The standardized dichromate solution is then titrated against a sample of the acidified tin(II) chloride solution (You will do this step in the next question). Evidence TITRATION OF IRON(lI) SOLUTION (volume of K2Cr2O7(aq) required to react with 15.00 ml of 0.07 mol/L Fe2+(aq)) Trial 1 2 3 4Final buretreading(ml) 13.8 24.4 35.2 45.9Initial buretreading (ml) 2.3 13.8 24.4 35.2Find the concentration of the Cr2O72-(aq) in mol/L: (give your answer to 4 decimal places)

Answer 1

Answer:

Follows are the solution to the given question:

Explanation:

Following are the balanced redox equation:

$Cr_2O_7^{2-} + 6 Fe^{2+} + 14H^{+} \to 2Cr^{3+} + 6 Fe^{3+} + 7H_2O$

Calculating the average volume of the dichromate:

$(i)\ 13.8 - 2.3 = 11.5 \ ml\\\\(ii)\ 24.4 - 13.8 = 10.6\ ml\\\\(ii)\ 35.2 - 24.4 = 10.8 \ ml\\\\(iv)\ 45.9 - 35.2 = 10.7\ ml$

$Mean\ volume = 10.9\ ml = 0.0109\ L\\\\moles\ Fe^{2+} \ titrated = 0.01500 \ L \times 0.07\ \frac{mol}{L} = 0.00105 \\\\moles\ Cr_2O_7^{2-}\ required = 0.00105\ mol\ Fe^{2+} \times 1 \ mol\ \frac{Cr_2O_7^{2-}}{6 \mol\ Fe^{2+} } = 0.000175 \ moles\ Cr_2O_7^{2-}\\\\Concentration \ of\ Cr_2O_7^{2-} = \frac{0.000175\ moles}{0.0109\ L} = 0.01606\ M$