I am getting stuck with finding the mols, grams and percent of Cr^3+

To measure the iron content of runoff from a ranch a 25.0 mL sample of run off was acidified with HNO3 and treated with excess KSCN to form a red complex.  (KSCN itself is colorless.)  The solution was then diluted to 100 mL and put into a variable pathlenght cell.  For comparison, a 10.0 mL reference sample of 6.80 x 10-4 M Fe3+ was treated with HNO3 and KSCN and diluted to 50.0 mL.  The reference was placed in a cell with a 1.00 cm pathlenght.  The runoff had the same absorbance as the reference when the pathlenght of the runoff cell was 2.48 cm.  What wa the concentraton of iron in the runoff?

Potentially Useful Information Spectrochemical Series: | < Br < SCN < Cl° < NO3¯< F° < OH° < C2O4²- ~ H2O < NCS < NH3 < en < PPH3 A student synthesizes and isolates the following coordination compound [Ni(H2NCH2CH2NH2)3]Cl2 (molar mass = 309.8966 g/mol) according to the balanced reaction below. In the experiment, the student reacts 2.500 g of nickel (II) chloride hexahydrate (molar mass = 237.6878 g/mol) with 4.000 g of ethylenediamine (molar mass = 60.0992 g/mol). After isolating the product, the student collects 3.200 g of the nickel coordination compound. NICI2•6H2O (aq) + 3H2NCH2CH2NH2 (1) → [Ni(H2NCH2CH2NH2)3]Cl2 (s) + 6H2O (1) What is the limiting reactant in the reaction above? In this reaction, the limiting reactant is... O ethylenediamine O nickel (II) chloride hexahydrate O This reaction is stoichiometric, so there is no limiting reactant.

A Chemist collected a 0.4891-g sample of an ore for Fe determination by a redox titration with K2Cr2O7.The ore was carefully crushed prior to weighing and dissolved in HCl and using a Jones reductor the ironin the sample was brought into the +2 oxidation state. After titration with diphenylamine sulfonic acid,itrequired 36.92 mL of 0.02153 M K2Cr2O7 to reach the end point. Calculate the iron content of the ore as%w/w Fe2O3

A Chemist collected a 0.4891-g sample of an ore for Fe determination by a redox titration with K2Cr2O7.The ore was carefully crushed prior to weighing and dissolved in HCl and using a Jones reductor the ironin the sample was brought into the +2 oxidation state. After titration with diphenylamine sulfonic acid,itrequired 36.92 mL of 0.02153 M K2Cr2O7 to reach the end point. Show your solution why 77.86% is the iron content of the ore as %w/w Fe2O3.

Use the data provided for stock concentration and mass to calculate the concentrations of each solution.  Solution A) A stock solution of 0.0100 M solution of K3[Fe(CN)6] is provided. Calculate the volume of the stock solution needed to prepare 100.0 ml of .00200 M K3[Fe(CN)6]. Deionized water should be used to dilute the solution. Solution B) Calculate the volume of solution A needed to prepare 50.0 ml of .0010 M K3[Fe(CN)6]. Deionized water should be used to dilute this solution.

K2Cr2O7 + 7H2C2O4·2H2O → 2K(Cr(C2O4)2(H2O)2) + 6CO2 + 17H2O Calculate theoretical yield of: K[Cr(C204)2(H20)2] · 2H2O (3 g of oxalic acid dihydrate (H2C2O4·2H2O) )(1 g of potassium dichromate (K2Cr2O7) )(20 mL of 95% ethanol)

An alloy containing Ni, Fe and Cr was analyzed by a complexation titration using EDTA as titrant. A 0.7176 g sample of the alloy was dissolved in HNO3 and diluted to 250 mL in a flask. A 50.00 mL aliquot of the sample, treated with pyrophosphate to mask Fe and Cr, required 26.14 mL of 0.05831 M EDTA to reach the murexide endpoint. A second 50.00 mL aliquot was treated with hexamethylenetetramine to mask Cr and titration with 0.05831 M EDTA required 35.43 mL to reach the murexide endpoint. Finally, a third 50.00 mL aliquot was treated with 50.00 mL of 0.05831 M EDTA and titrated back to the murexide endpoint with 6.21 mL of 0.06316 M Cu(II). the weight percentages of Ni, Fe and Cr in the alloy.

A 5.07-g petroleum specimen was decomposed by wet ashing and subsequently diluted to 500. mL in a volumetric flask. Cobalt was determined by treating 25.00-mL aliquots of this diluted solution as follows: Reagent Volume in mL           Co(II), 3.00 ppm       Ligand     H2O         Absorbance      0.00 20.00 5.00 0.416 5.00 20.00 0.00 0.522   Assume that the /ligand chelate obeys Beer’s law and calculate the percentage of cobalt in the original sample.

b) It was determined that the coordination compound (from above) also contained ammonia, NH3. In order to determine the ammonia content, the student weighed 0.2307 g of the coordination compound and thermally decomposed it to release the ammonia. The ammonia was collected in a flask containing 25.00 mL of 0.3120 M HCI. The solution was then titrated with standardized NaOH solution of 0.2512 M. It took 10.45 ml of the NaOH solution to reach to the endpoint. Determine the % ammonia in the coordination compound.