An alloy sample weighing 5.0g contains Cr. The Cr is chemicallyconverted to a K2Cr207 solution. The Cr207^2- ion in the solutionis completely and exactly converted to Cr^3+ by reacting it with4.73g of I2. What is the % Cr in the alloy?
Need to balance: Cr207^2- + I2 ---> Cr^3+ + IO3^-

You want to prepare 450.0 ml of a 145 pm K+ ion solution. Thedensity of the solution is 1.01g/mL. Disposal solution is 0.728MK2SO4. How many mL of the K2SO4 do you need to use?

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Elin HesselLv2

3 Aug 2019

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Method 1: Titration with Potassium Permanganate
5 H2O2 + 2 MnO4- + 6 H+ --> 8 H2O + 5 O2 + 2 Mn2+
Method 2: Catalytic Decomposition to Water and Oxygen
2 H2O2 --> 2 H2O + O2
Method 3: Oxidation of Iodide to Iodine; Spectroscopic measurement of TriIodide ion.
IO3- + 5 I- + 6 H+ --> 3 H2O + 3 I2 (standard)
H2O2 + 2 I- + 2 H+ --> 2 H2O + I2 (unknown)
I- + I2 --> I3-
Method 1:
You weigh out Potassium Permanganate,
Mass of KMnO4 (MW=158.034).......... 0.1736 g
You dissolve it completely in water.......... 46.00 mL
(a) Molarity of MnO4- solution........................... ________________ M
You pipet out your UNKNOWN............. 0.90 mL
You acidify and titrate it with your KMnO4 solution until the permanganate color persists.
Volume of permanganate solution.......... 11.39 mL
(b) Molarity of the HOOH in the UNKNOWN...................................._____________ M
Method 2:
You pipet your UNKNOWN into a reaction tube.... 4.40 mL
Add a "boat" containing Manganese Dioxide, MnO2
Set up the gas collection apparatus shown on the right.
You sink the boat and allow the oxygen generated to collect in the collection flask. The water temperature is................. 27 oC
The Barometric Pressure is............... 761.9 mm Hg
Weight of the collection Flask with remaining water.... 154.81 g.
Weight of collection flask filled with water........... 200.70 g.
DensityH2O ................................. 0.996 g/cc

(c) Partial Pressure of Oxygen collected................................. ____________ mm Hg
(d) Volume of oxygen collected ...................................... ____________ mL
(e) Millimoles of oxygen gas generated.................................. ____________ mmol
(f) Molarity of Hydrogen Peroxide in UNKNOWN.......................... ____________ M
Method 3:
STANDARD: Put into a clean 250 mL volumetric flask exactly ..... 1.00 ml
of 0.95 mM iodate STANDARD.
Add an excess of 1M KI and 1M Sulfuric Acid and let stand for 5 minutes. Dilute to volume.
UNKNOWN: Pipet into a clean 250 mL volumetric flask 1.00 mL of your UNKNOWN and dilute to volume with distilled water.
Put into a clean 250 mL volumetric flask exactly ........ 1.00 mL
of this diluted H2O2 UNKNOWN.Add an excess of 1M KI and 1M Sulfuric Acid and let stand for 5 minutes. Dilute to volume (250 mL). Measure STANDARD and UNKNOWN spectroscopically at 360 nm using the same cuvet throughout.
% Transmission of BLANK.................................. 98.1 %
% Transmission of STANDARD................................ 48.5 %
% Transmission of UNKNOWN................................. 34.7 %
(g) Absorbance of STANDARD.................................... ___________________
(h) Absorbance of UNKNOWN.................................... ___________________
(i) Molarity of original UNKNOWN................................. ___________________ M

Please help with explanation:

For each reactant, comment on the spread of values of the order of reaction generated by using the differential rate law, and your confidence in assuming a value of one or two. Also, consider the form of the two best-fit curves generated by use of the integrated rate law, to justify your choice of one or two as the order of reaction. Finally, comment on the correlation between the results from the differential rate law and those from the integrated rate law.

OTHER INFORMATION

PROCEDURE

You will be provided with two stock solutions, A and B. Solution A contains iodate ions and solution B contains sulfite ions along with some acid and starch. Note the concentration of each stock solution on your data sheet. In preparing your reaction systems, always add water first, followed by solution B, then add solution A.

Calculate the total volume of each needed reagent needed and record it on your data sheet. Pour approximately that amount from the reagent bottle into an appropriate size beaker. If you accidentally take too much, offer the extra to another group to minimize waste. For water, use distilled water.

Use 5.00 and 10.00 mL graduated pipets to measure out the larger volumes and 1.00 mL graduated pipets to measure out smaller volumes. Use a small (<250mL) beaker as your reaction vessel. Always add acid to water, never the other way around otherwise it can spatter and result in injury.

As temperature changes affect reaction rates, you will want to minimize contact with the solutions. After combining water and solution B, begin stirring using a glass stirring rod while another group member quickly adds solution A. Make sure the stopwatch is started as soon as solution A is added. Time each reaction using the stopwatch and record the time in ink on your data sheet. Record the temperature of the room for the reactions.

Reaction IO₃^- + 3 SO₃^-2 ------------> I^- + 3 SO₄^-2

Endpoint Rxn 1 IO₃^- + 5 I^- + 6 H⁺ -------------> 3 I₂ + 3 H₂O

Endpoint Rxn 2 starch + I₂ -------------> starch-iodine complex

Iâve attached the lab procedures

Could I get some help with the questions please

Weigh boat is 2.20g

Weigh boat + copper is 2.43g