answers

watching

views

18 Nov 2019

Potassium permanganate, a strong oxidizing agent, is commonly used in titrations because of its significant purple hue in solution. An experiment was performed in which a sample of iron(II) chloride (FeCl2) was dissolved in water and titrated with potassium permanganate (KMnO4) according to the following balanced equation. KMnO4(aq) + 8 HCl(aq) + 5 FeCl2(aq) â MnCl2(aq) + 5 FeCl3(aq) + 4 H2O(l) + KCl(aq) If 28.64 mL of 0.1110 M KMnO4 was added to the solution to reach the end point, what mass of FeCl2 was in the sample?

answers

watching

views

For unlimited access to Homework Help, a Homework+ subscription is required.

You have 0 free answers left.
Get unlimited access to 3.8 million step-by-step answers.

Get unlimited access

Already have an account? Log in

nguyentiendat040305Lv2

17 May 2022

Unlock all answers

Get 1 free homework help answer.

Get unlimited access

Already have an account? Log in

You have 0 free answers left.
Get unlimited access to 3.8 million step-by-step answers.

Get unlimited access

Already have an account? Log in

Jamar FerryLv2

7 Feb 2019

Get unlimited access

Already have an account? Log in

Join us on Discord

Chemistry Study Group

Join now

Related questions

Be sure to answer all parts. The active agent in many hair bleaches is hydrogen peroxide. The amount of H2O2 in 14.5âg of hair bleach was determined by titration with a standard potassium permanganate solution: 2 MnO4â(aq) + 5 H2O2(aq) + 6 H+(aq) â 5 O2(g) + 2 Mn2+(aq) + 8 H2O(l) (a) For the titration, how many moles of MnO4â were required if 40.8 mL of 0.154 M KMnO4 was needed to reach the end point? Write your answer to the correct number of significant figures. Enter your answer in scientific notation. ______ Ã 10 mol MnO4â (b) How many moles of H2O2 were present in the 14.5 g sample of bleach? Write your answer to the correct number of significant figures. ____ mol H2O2

beigeweasel930

VSEPR theory predicts that the molecular geometry (shape) of XeF₄ is

A. square planar

B. square pyramidal

C. trigonal bipyramidal

D. t-shaped

_____ 20. In the vinegar titration experiment, the student does not fill the buret tip before titrating. How would this affect the molar concentration calculation of the acetic acid?

A. No change

B. The molarity would increase.

C. The molarity would decease.

D. The indicator would not work properly.

_____ 21. Which of the following statements is incorrect?

A. An acidic solution turns blue litmus paper red.

B. A basic (or alkaline) solution turns red litmus paper blue.

C. Phenolphthalein is pink in acidic solution but colorless in basic solution.

D. Phenolphthalein is pink in basic solution but colorless in acidic solution.

A student carried out the Synthesis of Alum experiment and obtained a percent yield

of 62.1%. If the mass of the student's product was 3.916 g, calculate the student's

theoretical yield for alum.

4. Tartaric acid, H₆C₄O₆ (aq), is present in grapes and unripe fruit and reacts with potassium permanganate, KMnO₄, and hydrochloric acid in the following way:

2 KMnO₄ (aq) + H₆C₄O₆ (aq)Â + 6 HCl (aq) Ã 2 MnCl₂ (aq) + 2 KCl (aq) + 6 H₂O (l) + 4 CO₂ (g)

An unknown sample containing tartaric acid reacts with excess potassium permanganate at 22.0Â°C and 680.0 mmHg. The resulting carbon dioxide gas was collected under conditions similar to the Analysis of Alka-Seltzer experiment carried out in lab.

(3) a. If the vapor pressure of water at 22.0Â°C is 19.8 mmHg, what is the pressure of the carbon dioxide gas in the experiment described above?

(5) b. If the volume of carbon dioxide obtained is 39.15 mL, calculate the number of moles of carbon dioxide gas.

(4) c. What mass of tartaric acid must be present in the experiment described above?

(4) d. What is the mass percent of tartaric acid in the unknown sample if 0.1200 g of the unknown was used?

INTRODUCTION

Many transition metal cations can have more than one possible charge (Worksheet 1). Differently charged species of the same element can have different chemical and physical properties. Knowing the charge can allow separation of the different ions based on their properties. For example, Cu²⁺ is blue and stable in solution, while Cu⁺ is colorless and reacts with oxygen. Hemoglobin contains iron as Fe²⁺, but it is inactive at binding oxygen when the iron gets oxidized to Fe³⁺. There are many similar situations in which it is important to always properly indicate charges of ions.

This laboratory experiment uses the difference in chemical properties of Fe²⁺, iron(II), and Fe³⁺, iron(III), to quantify the amount of each present in a solution of unknown concentrations of each. You will first determine the amount of iron(II) in your sample by titrating with a reagent that does not react with iron(III). You will then titrate a second sample after converting all the iron(III) to iron(II) in order to determine the total iron present. The percent composition of Fe²⁺ in the unknown mixture will be calculated.

BACKGROUND

The concentrations of both iron(II) and iron(III) ions in a solution can be determined by titration with potassium permanganate. The reaction is an oxidation-reduction reaction, or redox, for short. A brief introduction to oxidation-reduction reactions is given in the background of the âAcids and Basesâ experiment. The permanganate ion effectively oxidizes iron(II) to iron(III) in an acidic solution while being reduced to manganese(II) ion. The balanced net ionic reaction is:

5 Fe²⁺(aq) + MnO4^â(aq) + 8 H⁺(aq) â 5 Fe³⁺(aq) + Mn²⁺(aq) + 4 H₂O(l)

Iron(III) is not oxidized by the permanganate ion, and thus does not react. Thus in order to determine the concentration of iron(III) ions, they must first be reduced to iron(II) ions. Zinc metal is used as the reducing agent, also under acidic conditions.

Zn(s) + 2 Fe³⁺(aq) â 2 Fe²⁺(aq) + Zn²⁺(aq) (reduction of the Fe3+)

Zn(s) + 2 H⁺(aq) â Zn²⁺(aq) + H₂(g) (a side reaction that oxidizes excess Zn)

The Zn2+ formed does not interfere with the subsequent titration because Zn2+ is not oxidized by permanganate. Notice that converting all the iron(III) to iron(II) means that the total iron concentration ([Fe2+] + [Fe3+]) is titrated, not just the iron(II) originally present.

Techniques

This is a lab will utilize several of the techniques introduced in the experiment âLaboratory Techniques and Measurements,â the procedures for which are given in Appendix B. Poor laboratory technique and misuse of the glassware will result in poor data results, which will affect the grade you receive on the laboratory report. In order to use your time efficiently in lab, review how to properly:

rinse glassware prepare a standard solution use a volumetric pipette

weigh by difference set up and use a burette use a graduated cylinder

heat samples on a hot plate

Analysis of Iron by Oxidation-Reduction Titration

This lab uses the common quantitative technique of titration. The only difference between the titration you will be doing in this lab and that done in the Molar Mass of a Known Acid lab is the type of reaction used: this lab will use a redox reaction in place of the acid-base reaction performed in the previous experiment.

In order to determine the concentrations of iron(II) and iron(III) ions in a solution containing both ions, two portions of the same sample must be titrated separately. This first titration will determine only the iron(II) concentration. A second sample will be treated with zinc metal in order to reduce the iron(III) to iron(II). The resulting solution will be titrated with potassium permanganate. The result of this titration will give the total iron concentration in the sample. The difference between the first and second titration is the equal to the iron(III) concentration.

In this titration, potassium permanganate serves as its own indicator. The intense purple color of the permanganate solution becomes colorless when the permanganate is reduced to manganese(II). Thus, as iron(II) is oxidized with the addition of the permanganate solution from the burette it will impart a purple color that will fade. However, once there is no iron(II) left in solution a faint purple color will remain, marking the endpoint of the titration. This color can be slightly altered by the presence of iron(III), which is yellow in solution. Remember that iron(III) is generated by the reaction between iron(II) with permanganate, increasing the yellow appearance of the solution and which can interfere with the detection of the endpoint. Phosphoric acid is added to help minimize this effect.

pre lab questions: