Calcium Carbonate and Ca2+ Ions

Experiment. EDTA Titration of Ca2+ in an stranger root word Experiment. EDTA Titration of Ca2+ in an unnoticeable peeing system ingest modified 9/2012 Objective The most common multivalent every(prenominal)oy ions in natural weewee supplys be Ca2+ and Mg2+. In this investigate, you will find the essence niggardliness of atomic number 20 ions that potful react with EDTA with the assumptions that EDTA reacts 11 with alloy (Ca2+) ions. Equipment 250-mL Erlenmeyer flask (3) 50-mL burette Ring-stand and difficultware Desiccator 400-mL Beaker 500-mL Vol. flask 250-mL Vol. flask 1. 0-mL Vol Pipette ascorbic acid-mL potash alum cylinder Hot plate Safety and Waste DisposalChemicals Buffer (pH 10) tack on 142 mL of 28 wt % aqueous NH3 to 17. 5 g of NH4Cl and swerve to 250 mL with piddle. Eriochrome black T indicator Dissolve 0. 2 g of the unassai testing groundle indicator in 15 mL of triethanolamine plus 5 mL of absolute ethanol. 50 wt % NaOH Dissolve 100 g of NaOH in 1 00 g of H2O in a 250-mL plastic bottle. Store tightly capped. When you remove radical with a pipet, try not to disturb the solidity Na2CO3 precipitate. Discussion Hard water is due to metal ions (minerals) that are fade out in the ground water. These minerals include Ca2+, Mg2+, Fe3+, SO42-, and HCO3-.Generally rugged water arises because rainwater moves done limestone, CaCO3 underground that occurs in our area to the aquifer. This is why we prize hardness in terms of CaCO3. The concentration of the Ca2+ ions is greater than the concentration of any otherwise metal ion in our water. The determination of water hardness is routinely utilise to measure the quality of water that the general public uses. Originally, water hardness was defined as the measure of the capacity of the water to precipitate soap. Hard water is not a health hazard since the main chemical in hard water is calcium.People regularly take calcium supplements. In fact, hard water can be a source of infalli ble minerals (calcium and magnesium) that is necessary for good health. Indeed, the National Academy of Science go so distant as stating that that consuming extremely hard water could be a major contributor of calcium and magnesium to the diet. The problem with hard water is that it cause soap scum, clog pipes and clog boilers. Soap scum is create when the calcium ion binds with the soap. This causes an insoluble compound that precipitates to chance variable the scum you see.Soap actually softens hard water by removing the Ca2+ ions from the water. When hard water is heated, CaCO3 precipitates out, which then clogs pipes and industrial boilers. This leads to give out or damage and is expensive to remove. There are two slips of water hardness, temporary and permanent. Temporary hardness is due to the bicarbonate ion, HCO3-, being gravel in the water. This type of hardness can be removed by simmering the water to expel the CO2, as indicated by the following equation HCO3- (aq) ? H2O (l) + CO2 (g). Because bicarbonate can be removed it is separate as temporary hardness.Permanent hardness is due to the presence of the ions Ca2+, Mg+2, Fe3+ and SO4-2. Because boiling cannot eliminate this type of hardness, the water is said to be permanently hard. The get across below tapers the degree of hardness of the water in terms of its calcium carbonate concentration in ppm and grains. Hardness rating Soft strength Hard Hard Very Hard Concentration of Calcium carbonate (mg/L or ppm) 0 75 75 to cl 150 to 300 300 and greater Concentration of Calcium Carbonate (grains/US gallon) 0 to 5. 2 5. 2 to 10. 5 10. 5 to 21 21 and greaterPermanent hardness is usually determined by titrating it with a standard dissolving agent of ethylenediamminetetraacetic acid, EDTA. The EDTA is a complexing, or chelating agent used to capture the metal ions. This causes water to soften, but the metal ions however, are not removed from the water. EDTA simply binds the metal ions so tha t the ions do not precipitate to form soap scum. EDTA is a versatile chelating agent. A chelating agent is a snapper whose jettyecules can form several bonds to a single metal ion. Chelating agents are multidentate ligands.A ligand is a substance that binds with a metal ion to form a complex ion. Multi-dentate ligands are umteen clawed, holding onto the metal ion to form a very s tabular array complex. EDTA can form four or six bonds with a metal ion. It is often used in soaps and detergents because it forms complexes with calcium and magnesium ions. The ions in hard water are bound to the EDTA and cannot interfere with the ashening action of the soap or detergent. EDTA is also used in viandss. Certain enzymes are responsible for food spoilage. EDTA is used to remove metal ions from these enzymes.It is used to promote dissimulation guardianship in dried bananas, beans, chick peas, keep clams, pecan pie filling, frozen potatoes and canned shrimp. It is used to improve flavor retention in canned carbonate beverages, beer, salad dressings, mayonnaise, margarine, and sauces. It inhibits rancidity in salad dressings, mayonnaise, sauces and salad spreads. In this laboratory you will be asked to determine the entireness permanent hardness. EDTA grabs all the metal ions in the water, not just the Ca2+ ions. This gives us a valuate that is not truly the concentration of Ca2+ ions.This causes an experimental fracture of about 1%, which is acceptable due to the fuzzy end bespeaks in this type of titration. Erio-T indicator or Eriochrome Black-T indicator is used in this titration. When it is chelated or acidifies, it produces a Pink-Red solution. When it is not chelated and under basic conditions it is Blue. The cardinal pictures provide the end tip in this titration. There is a 1-drop difference of 0. 01 M EDTA between the first and second pictures and between the second and third pictures. 2 or three seconds were allowed for colors in the second and th ird pictures to climb up after adding the additional drop.In each case the solution was thoroughly mixed. This color change from wine red to violet to blue is due to the narrow nature of the complex. Experiment. EDTA Titration of Ca2+ in an unknown solution PROCEDURE Modified 9/2012 1. Dry Na2H2EDTA. 2H2O (FM 372. 24) at 80 C for 1 h and imperturbable in the desiccator. Accurately weigh out 0. 6 g and pick it with heating in 400 mL of water in a beaker. Cool to room temperature pour into a 500-mL volumetric flask. , mix and dilute to the mark. 2. You should practice finding the end point several times by adding a little tap water in a clean beaker and titrating with EDTA.Save a solution at the end point to use as a color comparison for other titrations. 3. Pipet a 1-mL sample of unknown into a 250-mL flask and fill to the mark with deionized water. Mix thoroughly. From this 250-mL commonplace solution draw 4, 50mL fractional part samples and place each aliquot in 250mL Erlen meyer flasks. To each sample, add 3 mL of pH 10 airplane pilot and 6 drops of Eriochrome black T indicator. To the first 50-ml solution, titrate with EDTA from a 50-mL burette and note when the color changes from wine red to blue. 4. Repeat the titration with the next three samples to find an accurate value of the total Ca2+ concentration.Perform a blank titration with 50 mL of distilled water and subtract the value of the blank from each leave. 5. Upon closure of the experiment, discard all solution in a chemical licentiousness bottle and wash out the glassware. Be sure to dry your buret in the upside down position.Calculations Analysis Analyte Ca2+The reaction of Ca2+ ions with H2EDTA2- takes place with a 11 stoichiometric ratio Ca2+ + EDTA2- ? At the end point of the titration, 1-equivalent of Ca2+ reacts with one equivalent of H2EDTA2-. 1 eqv Ca2+ = 1 eqv H2EDTA2- equivalent Ca2+ = H2EDTA2- Vol EDTA CaH2EDTA. Re bid that the analyte (we call this unknown solution) was pre pared by taking exactly 1-mL of the unknown solution and diluting in a 250-mL volumetric flask (we will call this the derivation solution) 50-mL aliquot (call this the analyte) of this solution was then titrated against EDTA. Note that the analyte concentration is equal to the beginning solution concentration. The mound Ca2+ in 1 mL aliquot unknown tidy sum of Ca2+ in 50mL Sample = H 2EDTA2? $ Vol EDTA $ = mol H 2EDTA2- = mol Ca2+in 50mL Analyte % % bunch of Ca2+ in 1mL of unknown = mol Ca2+ ? 250mL aliquot Ca2+ __ g Ca2+ ? 50mL Analyte mol ? ? Dilution Factor Atomic mass Ca Mass of Ca2+ in 1 L solution Mass Ca2+ in 1 L = mass Ca2+ in 1 mL Aliquot 1000 mL 1 mL Concentration of unknown by percent (mv), part per hundred (mv) and Molarity (M) Mass Ca in 1mL aliquot Vol aliquot solution used % Ca2+ mv = 100 ppm Ca2+ mv = Mass Ca in 1mL aliquot Vol aliquot solution used 106 Molarity Ca2+ = mass Ca2+ in 1mL 1 mol Ca __g Ca ? ? ? molar mass Ca 1 vividness in L of unknown Aliquot used Mass in grams of calcium carbonate unknown in 1L solution Mass CaCO 3 in 1-L = mass ppt (g) 1 mol CaC 2O 4 H 2O __ g CaC 2O 4 H 2O ? molar mass CaC O H O 2 4 2 1 mol CaCO 3 1 mol CaC 2O 4 H 2O 1 mol CaCO 3 Vol in L of aliquot ? ? ? ? Molar mass CaCO 3 __ g CaCO 3 1L Dilution Factor statistical Analysis 1. Report the mean, medium, standard deviations (s), relative standard deviation (RSD), magnetic variation (s2) and the 95% confidence time interval for your results. 2. 3. 4. Apply the students t test at the 95% confidence interval Apply a Q-test to any suspected result. Confidence interval = x + ts n 5. equate the results of this experiment to the previous experiment, Gravimetric determination of Ca. Apply the Comparison of elbow room with Students t, Case2 (p76) Comparing Replicate Measurements. Do the two methods take hold within the 95% confidence interval? Test for Outlier Apply a Grubbs Test and Q-Test for any suspected outliers at 95 % level. conceive page 83 of text for critical values for 95% confidence.If your results show an anomalous data then use the Q-test to determine if the result should be rejected. Q= (Suspected Value Nearest Value) (Suspected Value Furthest Value) G calc = Questionable value x s Table of Data, Results and Statistical Analysis Calcium lovesome Data 1. Unknown number 2 Mass of EDTA used 3 Concentration of EDTA 4 Volume of Unknown Ca2+ Solution 5 Volume EDTA during titration 6 Volume EDTA for blank trials 7 Q-Test (95%) of any outlier Analysis and Results 8 Mass of calcium in 1-mL aliquot (Average) 9 Mass of calcium in 1-L solution (Average) 10 Conc. of calcium, %, ppm (mv) and Molarity (Average) 11 Mass of calcium carbonate in 1-L (Average) Statistical Analysis 12 Averages and Standard deviations of all results 13 naval division, RSD and CV of all results 14 95% Confidence interval 15 ttable and tcalc for replicate measurementsDiscussionThe remnant of this experiment was to determine the hardness of the unknown sample by calculating the concentration of calcium ions in an analyte solution. Correcting for dilution factors, the concentration of calcium in the unknown in g/L is to be determined and compared to analysis for calcium by EDTA titration. Statistical analysis is utilise to the results. A discussion of this experiment should include the accuracy and precision of this experiment compared to the EDTA titration method. An analysis of a comparison of replicated measurement is performed and discussed. Table of results should include acknowledge in your summary table the following i) Moles of Ca2+ in the unknown and the ordinary equivalent value. ii) Concentration of Ca2+ in the unknown in molarity, ppm and g/L iv) Mean, standard deviations, RSD and CV for each of the above concentration units. v) Students t at the 95% confidence interval vi) Application of a G and Q-test to any suspected result at the 95% level. vii) ttable, tcalc, cobblers last on comparison of replicated measurements.Experiment. EDTA Titration of Ca2+ in an unknown solution Modified 9/2012 Sample data table. Sample Unknown ______ Mass Na2EDTA, (g) Molarity Na2EDTA, (M) Vol. unknown, (ml) Buret Volinitial, (ml) Buret Vol closing, (ml) Volume EDTA used, (ml) Vol EDTA for blank, (ml) Corrected Col EDTA, (ml) ravel 1 Mass Ca2+ in 1 ml aliquot (g) Mass Ca2+ in 1-L solution (g) Concentration Ca (%) Concentration Ca (ppm) Molarity Ca2+, unknown (M) Mass calcium carbonate in 1L Q and G Test for Outliner CaCO3 (g/L), unknown Trial 2 Trial 3 Trial 4 Average Std dev Variance RSD , CV 95% CL Trial 1 Trial 2 Trial 3 Trial 4 Blank Students t Analysis Comparing replicate measurements Analysis A CaCO3 (g/L) 1 2 3 4 Trial 1 Trial 2 Trial 3 Trial 4 Avg Avg X1bar X2bar Sqrt ((n1*n2)/(n1+n2)) (xi-x1)2 deg freedom Spooled Expt 2 Expt 3 Ex2 (Xi-Xbar)2 Ex3 (Xi-Xbar)2 T calc t table closedown T calc ? T table, at 95%, two result are (not) considered to be different EDTA Titration of Ca2+ in an unknown solution. 1 2 CRITERIA (Tentative point distribution may change depending on experiment) Quiz / Homework NONE foundation garment and ProceduresA. IntroductionObjective of Expt.Background information.Math relationship used in study.B. ProceduresOutline of procedures in Expt.Flow chart pictorial of procedures. adjective changes.Information (data) to be recorded during experiment. (to be presented in Table form. )Safety and disposal information. This instalment of the report should be turned in before the start of lab class (prelab discussion). Data, Observe. , Results and Calc.C. Data and ObservationData in table form. & detailed observations written in the table. All data entry should contain the proper number of profound figures and units. Data should always be recorded in an organize fashion.Balance chemical equations all chemical reaction which occurred during an experiment should be written in this prick. Then it should also be written in the discussion piec e of the report. This portion of the report should be turned in before you disappear the science lab.Calculations & ResultsD. CalculationsSample calculation shown with Excel spreadsheet available with formulas shownStatistical analysis of data and result. Avg, Std dev, RSD, CVE. ResultsSummary of Result(s) in table form. In this section accuracy of results is very pregnant as headspring as detailed calculation showing how the result was obtain. Unknown will also be included in this section. Discussion / Conclusions and Post-Lab QuestionsF. Discussion (Talking points)What is your final result in this experiment. Are the four trials consistent with each other? If not what would account for the inconsistencies? How did the results in this experimental result compare to the result in experiment 2? Is your result for the amount of calcium carbonate in your unknown within the range of 10 25 g/L? Elaborate on this. What is the average amount of calcium in tap water, how much more high er is this unknown compared to the average heart and soul in tap water (express in %).G. ConclusionSummary of the goal of the experiment and how that goal was achieved in the experiment. H. Post-lab questions or Editorial commentWhat did you learn in this experiment? What skills in lab practice did you develop through this expt? This portion (Calculation and Discussion) is turned in at the beginning of class of the due-date Overall Presentation (of lab notebook)Lab proficiency during experiment example are, class preparation, safety glasses precautions and leaving the laboratory clean.Report presentation examples are the headings of each report that includes name, title, lab partner, date and section , witness signature. Legibility of report. Is the report easy to read or is important information jotted down by small print in the corners of the lab report. The overall impression is important. Lab TechniqueSafety wear goggles, handle chemicals with caution, proper discourse of lab equipmentLeave lab clean and tidy