Answer Happy

(1) Which acid is the source of the protons (H) consumed in the reaction? (2) Based on your RMD, what can you state about the precision of your percent iron (II) value? About the accuracy of your value?

Each pair of students will titrate two aliquots Rinse the sides of a clean 50-ml buret with about 5-mL Concentration KMnO4: portions of potassium permanganate (KMnO4) solution provided. Record concentration! 1.857x102 Fill the buret and clamp the buret to a ring stand. Make sure to eliminate air bubbles from the nozzle and valve. Remove any drops adhering to the buret tip by touching the tip to a clean beaker. Trial 1 Initial reading: ,00 mL Final reading: 19.72 mL Trial 1 Volume added: 19.72 ml Trial 2 Record the initial buret reading to 2 decimal places, e.g. 0.18 mL. Titrate the first sample with the potassium permanganate solution until a faint pink color persists for at least 30 seconds upon swirling. Calculate volume of potassium permanganate solution added. Record the new initial buret reading. Make sure you have enough potassium permanganate solution to complete the titration! Titrate the second sample with the potassium permanganate solution. Calculate volume of potassium permanganate solution added. Difference between volumes for Trials 1 & 2 Compare with your partner pair. If all volumes are within 1.0 mL, stop. Oth do one more titration. Initial reading:19.72 mL Final reading: 38.08 mL Trial 2 Volume added: 18:36 mL 1.35 mL Trial 3 (if needed) Initial reading: 18.92 mL Final reading: 36.20 mL Trial 3 Volume added: 17.28 ml

Procedure Record in Your Notebook Two pairs of students will prepare one solution of unknown Obtain an unknown iron (II) salt and record the unknown Unknown #: 37 number. Weigh out mass of unknown as specified by instructor Mass unknown: 4.9 (record to the nearest 0.1 mg) Transfer unknown to a 250-ml volumetric flask. 09 Add deionized water to dissolve the solid in two steps: In the first step, only partially fill flask so that the mixture can be swirled to mix. After dissolving the solid, fill to 250.0-mL mark. Use a dropper to help you add the water up to the fill-line. The bottom of the meniscus should be level with the line. Stopper and invert to mix contents. Pipet 50.00-ml aliquots into each of four clean 250-ml Erlenmeyer flasks. To each flask add 20.0 mL of 1.25 MH2SO4 solution and 5.0 mL of concentrated H3PO4 solution.