I need help on questions 2-4? NOTE: You may never use the dilution equation in place of stoichiometry for a reaction.1) A 10.00 mL aliquot of 0.010 M CaCO3 is titrated with 18.22 mL of EDTA solution. What is theEDTA molarity?2) A 100.0 mL water sample required 15.00 mL of EDTA solution during trial 1. What would be anappropriate volume to use during trial 2?(Note: You must read the full lab document to know how to answer this question, as it is alwaysassumed that you answer these in the context of the lab being performed. This means youshould have already read the whole lab document and written out your lab procedure beforestarting these prelab questions.)3) A 250.0 mL water sample requires 30.85 mL of the EDTA solution from question 1 to reach thecalmagite endpoint. What was the molarity of the hard metal ions in the water sample?4) If the metal ions in the water sample of question 2 are assumed to be Ca²+ from CaCO3, expressthe concentration in ppm CaCO3. This is the same as the concentration in units of mg CaCO3 perliter of sample. PROCEDUREPART A-STANDARDIZATIONObtain a buret and a buret clamp from the equipment cart. Treat the burets with great care, especiallythe fragile tips. Rinse the buret with distilled water, then secure it to a vertical stand with the clamp.Assign one of your beakers to collect rinsings. Use distilled water to verify that the stopcock functionsproperly with no leaks or air bubbles.Use a small beaker to transfer EDTA solution from the reservoir to the buret. Take EDTA only as youneed it to avoid wasting excess. Rinse the buret with very small portions of EDTA before filling. To findthe molarity of the EDTA it will be used to titrate a known concentration of CaCO3. Use a 50 mL beakerto obtain about 40 mL of the CaCO3 standard solution from the cart. Use a transfer pipet to deliver 10.00mL of the standard into a clean 125 mL or 250 mL Erlenmeyer flask. Use a graduated pipet to add 5 mLof pH 10 buffer (The instructor may have set out a beaker and pipet for the entire class to use with thebuffer). Next add 3-5 drops of the calmagite indicator. The standard solution has been laced with Mg²+so the solution should appear red-pink.Record the initial liquid level in the buret. All readings should be recorded to the nearest 0.01 mL. AddEDTA to the flask until the indicator changes from red-pink to "purple", slow down because you want tostop just barely when it turns a more blue-purple. Some may find this endpoint difficult to see at first. Onthe verge of the endpoint the color is a somewhat complex mixture. Focus on the elimination of traces ofredness in it. It may help to compare the color to an untitrated (next) sample, and to save previouslytitrated samples. Record the final buret volume. Repeat the process for a second and third trial. Refillthe buret between trials. Each partner should do at least one standard titration.Try to perform operations consistently to enhance precision but do not be overly concerned if it is nothigh. Several factors including the low concentrations and interference from the buffer work againstobtaining a sharp endpoint.PART BUNKNOWN ANALYSISIn this experiment, you are usually given the option to use your own untreated water sample or to drawfrom a reservoir of lab tap water. Indicate the source of your sample (e.g., what city or water district or"lab water") in the report section. Due to the range of possible metal ion concentrations in the samples,choosing a good sample size may require a trial-and-error approach. Ideally, a sample would require 20-40 mL of EDTA to titrate. Start with a 50 or 100 mL sample for the first trial. As it should ideally requirebetween 20-40 mL of EDTA, if it does not, then you must adjust the sample size if necessary for theremaining trials. There will be points allotted for this during lab, so be ready to determine how much ofyour water sample to use for subsequent trials. Make sure to record the sample volume you use in eachcase. Before taking a sample, be sure that the source is well-mixed by shaking or swirling.Your instructor will indicate whether to use repeated transfers with a 50 mL pipet or with your 50 mLgraduated cylinder to deliver the sample volume into your 500 mL Erlenmeyer flask. Add buffer andindicator as with the standard. If at this stage, the sample solution does not give the red-pink color,consult your instructor. You will either be directed to choose an alternative sample source or beinstructed in a method to add an Mg²+ spike and perform a spike-plus-blank titration to correct for it.Assuming your sample did become wine red, titrate with EDTA as with the standard recording the buretlevels. If your group has one sample source, perform at least three titrations with it. If two partners wishto analyze samples from two different sources, perform two titrations on each. Then each partner shoulddetermine the average Ca²+ molarity for their source only and record it the postlab calculations section ofthe report.When finished, dispose of all solutions in the sink and rinse all glassware. Carefully return the buretsand pipets to the cart along with the buret clamps.

In complexometric titration, metal ion solution is treated with EDTA to form EDTA complex. Ca2+ +…

Answered: 2) A 100.0 mL water sample required…

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...