Experiment No. 2

Ion Exchange Separation and Titrimetric Determination of Nickel (II) and Zinc (II)

Juvinch R. Vicente

Cliff Jeffersonn C. Escobar

January 06, 2010

I. INTRODUCTION

Chromatography is a broad range of physical methods used to separate and or to analyze complex mixtures. The components to be separated are distributed between two phases: a stationary phase bed and a mobile phase which percolates through the stationary bed. It involves passing a mixture dissolved in the mobile phase through a stationary phase, which separates the analyte to be measured from other components in the mixture based on differential partitioning between the mobile and stationary phases.

Chromatography works on a simple principle. A mixture of various components enters a chromatography process, and the different components are flushed through the system at different rates. These differential rates of migration as the mixture moves over adsorptive materials provide separation. Repeated sorption/desorption acts that take place during the movement of the sample over the stationary phase determine the rates. The smaller the affinity a molecule has for the stationary phase, the shorter the time spent in a column. Thus, allowing the different components having different elution rate to separate.

There are a lot of chromatographic methods available nowadays. Their differences are brought about by the difference in the technique used, and on the attributes of the components being manipulated by the technique. Some of the common techniques used are by chromatographic bed shape (e.g. TLC and Paper chromatography), displacement chromatography, technique by physical state of the mobile phase (e.g. gas and liquid chromatography), affinity chromatography (e.g. Supercritical fluid Chromatography), technique by separation mechanism (e.g. Ion-exchange and Size-exclusion chromatography), and some other special techniques (e.g. Chiral chromatography and Reversed-phase chromatography).

Regardless of the wide variety of chromatographical techniques being used these days, nevertheless chromatography plays a common vital role in any chemical or bioprocessing industry, because the need to separate and purify a product from a complex mixture is a necessary and important step in the production line. Today, there exists a wide market of methods in which industries can accomplish these goals. However, chromatography is a very special separation process for a multitude of reasons. First of all, it can separate complex mixtures with great precision. Even very similar components, such as proteins that may only vary by a single amino acid, can be separated with chromatography. In fact, chromatography can purify basically any soluble or volatile substance if the right adsorbent material, carrier fluid, and operating conditions are employed. Second, chromatography can be used to separate delicate products since the conditions under which it is performed are not typically severe. For these reasons, chromatography is quite well suited to a variety of uses in the field of biotechnology, such as separating mixtures of proteins.

In this experiment, we are basically going to study one of the common types of chromatographical techniques which is the Ion-Exchange Chromatography. Ion exchange chromatography separates compounds based on net surface charge of the analytes. Molecules are classified as either anions (having a negative charge) or cations (having a positive charge). Some molecules (e.g., proteins) may have both an anionic and cationic group. A positively-charged support (anion exchanger) will bind a compound with an overall negative charge. Conversely, a negatively-charged support (cation exchanger) will bind a compound with an overall positive charge.

An ion-exchange resin consists of an insoluble matrix, acts primarily as the stationary phase with charge groups covalently attached. In this case, we will be using a strong base anion exchange resin which has an active site composed mainly of Quaternary Ammonium group. On the other hand, the unknown sample to be analyzed will serve as the mobile phase, and is composed of Ni (II) and Zn (II).

The main objective of this experiment is to separate and quantify the ions of the unknown sample. The separation of the two cations is based on differences in their tendency to form anionic complexes. At specific conditions, formation of metal complexes is selective.

After separation is complete, the metal cation species will be determined by compleximetric titration with standard EDTA solution. These titrations are based on complexation reactions between Metal ions and Ligands. Ligands are ions or molecules that bind to a metal atom to form a coordination complex (metal complexes). These are compounds in which a Central Metal atom is being surrounded by the Ligands. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. Thus, complexation reactions involves a Central metal atom as a Lewis acid (accepts electron pairs) and the ligands as Lewis bases (Donate Lewis pairs).

The nature of metal-ligand bonding can range from covalent to ionic. Furthermore, ligands are classified according to its Denticity. Denticity refers to the number of times a ligand bonds to a metal through non-contiguous donor sites. Monodentate ligands can bond to a metal only at a single donor site. Many ligands are Polydentate, which means they are capable of binding metal ions through multiple sites, usually because the ligands have lone pairs on more than one atom. Ligands that bind via more than one atom are often termed Chelates.

Ethylenediaminetetraacetic acid which is commonly known as EDTA is among the most important and widely used reagents in this titration. It is a hexadentate chelating agent having up to 6 donor sites (2 on N and 4 on COO-). EDTA forms an octahedral complex with most metal cations, M2+, in aqueous solution. The main reason that EDTA is used so extensively in the

analysis of metal cation solutions is that the formation constant for most metal cation-EDTA complexes is very high, meaning that the equilibrium for the general reaction lies far to the right:

M2+ + H4 [EDTA] → MH2 [EDTA] + 2H+

There are actually several reasons why carrying out the reaction in a basic solution is favoured. First, basic condition removes H+ as it is formed, which favours the formation of the EDTA-metal cation complex reaction product. Second, for the purposes of this experiment, the metal ion analysis will be determined for the EDTA-4 form, because this is the form that binds metals the best. Its reaction with the divalent metal M2+ is described in this equation:

M2+ + (EDTA)-4 → [M (EDTA)] 2-

EDTA-4 form only occurs when the pH of the solution is between 10 to 12 or so. As the pH gets lower, the % of EDTA in this form gets lower, so the binding of metal and EDTA also gets lower. So this condition is very much vital, and to achieve this, we are going to introduce basic pH Buffers to the analyte solution.

Finally, what makes EDTA a convenient reagent is chelating property; the fact that it always reacts with metals on the 1:1 basis, making calculations easy.

Several titration methods can be done using EDTA. These include direct titration, back titration, and displacement Titration. Direct titration involves addition of an appropriate indicator to a solution of the metal ion and simply titrated with EDTA. Back titration involves addition of an excess EDTA to the metal ion solution, and the excess EDTA is titrated with a known concentration of a second metal ion. Lastly the one used in this experiment, Displacement titration usually used for metal ions that do not have a good indicator. Here the analyte is treated with an excess of a second metal bound to EDTA. The analyte ion displaces the second metal from the EDTA complex, and then the second metal is titrated with EDTA. A typical displacement titration involves Zn(II) and other metal ions as the analyte and MgEDTA at the displacement titrant.

Another important thing about compleximetric titration is the indicator. In this experiment, the indicators to be used are different for each Metal ion species, Eriochrome Black T for Zn (II) and Murexide for Ni (II). Nevertheless, the indicators follow the same principle for both analyses. The indicators are added to the analyte solution. In the initial stages, Mg ions which forms the least stable EDTA complex are displaced from the EDTA complex by the analyte ions and are free to combine with the indicator, thus imparting a wine red or red violet color

(for EBT indicator) and yellow (for Murexide) to the solution. When all of the analyte ions have been complexed, however, the liberated magnesium ions again combine with EDTA the so the indicators changes back to its free form again and you can see the endpoint, blue (for EBT) and violet (Murexide).

The amount of the analytes present will be quantified in terms of mass in mg. Theoretically, the result should lie between 2mmol – 4mmol of each metal ion species. Which means that the solution should contain, around 117 – 235 mg of Ni(II), and around 131 mg – 262 mg Zn(II).

II. MATERIALS AND METHODS

2M HCl

Strong Base Anion Exchange Resin (Amberlite CG 400)

Glass Wool

6M NH3

Concentrated HCl

Standard 0.01 M EDTA solution

Freshly distilled water

pH-10 Buffer

Eriochrome Black T Indicator

Murexide Indicator

25 ml Burette

The resin column was prepared first by mixing around KUNG PILA MN ANG MASS NGA GIGAMIT of the Strong Base anion exchange resin (Amberlite CG 400) in around 50.0 mL of freshly distilled water. A roll of glass wool was then carefully plugged into the bottom of a 25-mL burette. The prepared resin was then poured into the burette properly so as to avoid hollow portions along the column, and sufficient enough to have a 10 cm – 15 cm column. The column was then washed with 50 mL NH3 (NH4OH form). This was followed by 100 mL of water and 100 mL of HCl. The flow rate in each washing was maintained at a very slow rate. Moreover, all throughout the preparation, the water level was controlled for it not to go below the level of the resin.

Before the start of the experiment, the unknown sample to be used was already prepared by our teacher. The sample contains Zinc (II) and Ni (II) solution at an unknown amount between 2.00 mmol – 4.00 mmol. Accurately 2.00 mL of the unknown sample was added with 16 mL of concentrated HCl and diluted to 100 mL in a volumetric flask. At this condition, the solution is approximately 2 M of the acid.

10.00 mL of the resulting solution was then transferred into the column and drained very slowly until the liquid level reaches approximately 1 cm above the resin level. The solution was allowed to stay for several minutes. The eluate was collected beneath the column by 250 mL Erlenmeyer flask. We then rinsed the column with 3 mL portions of 2 M HCl three times, lowering the liquid level just above the resin each run. The Nickel was then eluted with 50 mL of 2 M HCl at a flow rate of 2 – 3 mL per minute. After the elution, the eluate was then heated just to dryness on a hot plate. The Zinc was then eluted from the column using 100 mL of water at the same rate as Nickel’s. The eluate was collected using 500 Erlenmeyer flask.

During the drying process of the Nickel’s eluate, overheating was not allowed to avoid NiCl2 decompose into NiO. Upon dryness was reached, the residue was then dissolved in 100 mL of freshly distilled water. The solution was then added with pH-10 Buffer until the solution becomes basic (about pH of 10). Then about 0.2 g of Murexide indicator was added to the resulting solution. Titration was then done with EDTA as the titrant (color change from yellow to purple). Weight in milligrams of nickel in the unknown was then calculated.

To the eluate of Zinc, pH-10 Buffer was added until the solution becomes basic (about pH of 10). It was then added with Eriochrome Black T indicator and titrated with the standard EDTA solution (color change from wine red to blue). The weight in milligrams of Zinc in the unknown was also calculated.

All the data and results gathered were recorded and tabulated accordingly.

III. EXPERIMENTAL RESULTS

TABLE 1. Amount and Concentration of Reagents used

Mass ResinMolarity of EDTA Sol'n 0.009800 MVolume of the unknown Sample used 2.00 mL

TABLE 2. Standardization of EDTA solution

Mass CaCO3 0.1316 gMolar mass CaCO3 100.0869 g/molVolume Stock Solution 250 mLVolume Aliquot 50.0 mL Trial 1 Trial 2 Trial 3Initial Reading (mL) 0.00 0.00 0.00Final Reading (mL) 26.70 26.30 26.70Volume EDTA consumed (mL) 26.70 26.30 26.70Molarity EDTA (mol/L) 0.009751 0.009899 0.009751Average Molarity EDTA (mol/L) 0.009800

TABLE 3. Titrimetric Analysis of Nickel Using EDTA

Initial Reading (mL) 0.00Final Reading (mL) 1.90Volume EDTA consumed (mL) 1.90Moles Nickel (mmol) 9.31Mass Nickel (mg) 546.59

TABLE 4. Titrimetric Determination of Zinc using EDTA

Initial Reading (mL) 0.00Final Reading (mL) 1.70Volume EDTA consumed (mL) 1.70Moles Zinc (mmol) 8.33Mass Zinc (mg) 544.86

TABLE 5. Summarized Results:

TRIALVEDTA

Ni(II) (mL)VEDTA

Zn(II) (mL)Moles

Ni(II) (mol)Moles

Zn(II) (mol)Mass

Ni(II) (mg)Mass

Zn(II) (mg)1 1.80 --- 8.82 --- 518 ---2 2.50 2.00 12.3 9.80 719 6413 1.60 2.60 7.84 12.7 460 8334 1.10 --- 5.39 --- 316 ---5 1.90 1.70 9.31 8.33 547 5456 1.00 1.90 4.90 9.31 288 609

Average 8.09 10.1 475 657

IV. DISCUSSIONS AND CONCLUSIONS

This experiment aims to separate to separate cations Ni (II) and Zn (II), based on differences in their tendency to form anionic complexes with Chloride ions, using Ion-Exchange Chromatography. The method utilizes a strong base anion exchanger Amberlite CG 400, which was prepared by passing NH3 (NH4OH form), followed by HCl. The preparation is shown in Eq. 1.

(Preparation) Resin + NH4OH →RNH3OH + HCl →RNH3Cl + H2O Eq.1

Like strong acid resins, strong base resins are highly ionized and can be used over the entire pH range. The resin prepared has an immobilize active site which is a quaternary ammonium group and has a negatively charged chloride mobile anions which is available for the exchange.

Table 1 show all the amounts and concentrations of the reagents used in this experiment. Some reagents used were prepared by each group, while some were provided by the class monitors. EDTA solution was properly prepared and standardized using CaCO3 as primary standard. Standardization data of the EDTA solution is shown in Table 2. Standardization shows that the EDTA solution has an average molarity of 0.009800 M (see Cal. 1). The unknown solution was already prepared by our teacher before the start of the experiment.

During the preparation of the sample, 2 mL of the unknown solution was acidified to 2M acid. At this condition, Zn(II) ions form chlorocomplexes with HCl (chlorozincate(II) complexes). On the other hand, the condition is not appreciably suitable for the formation of any Ni(II) chlorocomplexes. Thus, Ni(II) ions will stay as free cations. The equation below illustrates the preparation of the sample:

(Complex-formation) Zn2+ + Ni2+ + 2M HCl → ZnClyx- + Ni2+ Eq. 2

where x and y are the net charge of the complex and the fraction of the Cl - ions in the complex respectively. As we can see, at specific concentration of the acid, the complex-formation becomes selective.

At this point, we have already established differences between the net surface charges between the two analytes, making Ion-Exchange Chromatography possible. Chlorozincate(II) complexes (such as ZnCl3

- and ZnCl4- ) have an overall negative surface charge, allowing them to

replace the mobile Cl- anions attached on the ammonium group, and therefore retained on the resin. Consequently, these released Cl- anions reacted with the free Ni (II) cations. The overall reaction mechanism of Nickel and Zinc is illustrated in Eq.3.

(Ion-exchange) xRNH3Cl + ZnClyx- + Ni2+ ↔ (RNH3

+) ZnClyx- + NiCl2 Eq.3

NiCl2 was then first eluted from the resin column by slowly passing portions of HCl through the column. At this point, we have successfully separated Nickel from Zinc. The eluate of nickel was collected using 250 mL Erlenmeyer flask. After separation of Ni (II) is complete, we then eluted Zn (II) from the column using freshly distilled water; elution with water effectively decomposes the chloro complexes and permits removal of the zinc. The eluate was collected using a 500 mL Erlenmeyer flask.

The eluate of Ni (II) was heated up to remove excess HCl; just to dryness since overheating will decompose NiCl2 into NiO. Decomposition of the analyte into oxide should not be allowed since Nickel in its oxide form does not react with the EDTA solution during titration. Also, study shows that Nickel oxides are cytotoxic which could have caused harm to us who performed the experiment. The residue was then dissolved in freshly distilled water and basified to pH 10 using the Buffer solution.

The solution was added with Murexide as its indicator, having an initial yellow color. It was then titrated slowly with the standard EDTA solution until the solution turned into violet. The titration process is shown in Eq. 4:

(Titration) Ni2+ + (EDTA) 4- → [Ni (EDTA)] 2- Eq.4

Table 3 shows the titrimetric analysis of Ni (II). The total volume of EDTA consumed was 1.90 mL for our group. Calculations revealed that the unknown sample has a total of 9.31 mol Ni(II) (see Cal. 2) which is equivalent to 547 mg of Ni (see Cal. 2). As we can see, the equation confirmed the 1:1 stoichiometric ratio of EDTA and the Metal ion.

The eluate obtained from Zn (II) was directly titrated with the EDTA solution with Eriochrome Black T as its indicator. Initially, the solution has a red wine color, upon reaching the end point the solution turned into pure blue. The titration process is shown in Eq. 5:

(Titration) Zn2+ + (EDTA) 4- → [Zn (EDTA)] 2- Eq.5

Table 4 shows the titirimetric analysis for Zn (II). The total volume of EDTA consumed by the titration for our group was 1.70 mL. Calculations revealed that the unknown sample has a total of 8.33 mol Zn(II) (see Cal. 3) and has an equivalent of 545 mg Zn (see Cal. 3). As with Ni(II), the stoichiometric ratio of EDTA and the Metal ion in this case is still 1:1.

As we can see in the calculation, we had a factor of100mL10mL

. This is because we only

took 10 mL of sample from the prepared 100 mL, so to get the overall amount of analyte from

the 100 mL solution the factor should be multiplied to the formula. Also, we can see a 100mL2mL

factor. This is because the sample that we analyzed is just 2 mL of the 100 mL unknown solution (stock solution) that was prepared. So since our task is to quantify how much metal ion species is present on the stock solution, we should multiply the formula by that factor.

During the titration of the Zn(II) eluate, 2 groups failed to reach end point. They persisted until they tried to check the pH of their analyte solution. They found out that their solution was still acidic. As discussed, EDTA titrations require a basic environment to make the reaction proceed. As a result, the 2 trials were eliminated from the set of data, reducing the no. of trials into just 4. However, the good thing is that the other groups have learned from their mistake.

The summarized results were shown in Table 5. Here we can see some possible outliers, and to know whether the values should be accepted or rejected we used Dixon’s Q test for outliers. Trials 2 and 6 of the mass of Ni (II) and trial 3 of the mass of Zn (II) (see Table 5) had undergone the test (see Cal. Blah2). The results revealed that all the suspected outliers must be accepted and retained. The table shows that the unknown sample has an average of 8.09 mol Ni(II) and 10.1 mol Zn(II), or an equivalent of 475 mg Ni(II) and 657 mg Zn(II).

Based on the data gathered and calculations done, we have concluded that like any Ion-exchange processes, Ion-exchange chromatography is stoichiometric and reversible. Moreover, if carried out properly this technique can be selective. Using this method, we have successfully separated the metal ion species Zn(II) and Ni(II). However, the results we obtained were quite far from the theoretical which is only between 2 – 4 mmol. Another thing we have learned is that pH is very much crucial in this kind of analysis, and thus it should be monitored carefully to avoid errors. Furthermore, we have also confirmed the chelating effect of our hexadentate titrant EDTA solution which is to bond with metals at 1:1 ratio.

V. QUESTIONS

1. Why it is important at all times to keep the water level above the top of the Ion-exchange column during the experiment?

- All throughout the experiment, the liquid level inside the column should not be allowed to drain below the resin level. This is to avoid channeling of beads in the column due to introduction to air. If allowed so, the resin column would form hollow portions. These portions will have no contact the analyte solution since the hollow portions are filled with air. Thus, the efficiency of the separation will decrease.

2. Describe the fundamental difference between ion-exchange and size-exclusion chromatography.

- Ion exchange chromatography separates compounds based on net surface charge of the analytes. This method is an adsorptive type of chromatographical techniques. The adsorption of the molecules to the solid support is driven by the ionic interaction between the oppositely charged ionic groups in the sample molecule and in the functional group on the support.

On the other hand, in Size Exclusion Chromatography is the separation technique based on the molecular size of the components. Separation is achieved by the differential exclusion from the pores of the packing material, of the sample molecules as they pass through a bed of porous particles. The principle feature of SEC is its gentle non-adsorptive interaction with the sample.

3. Devise a scheme for separating nickel and cobalt by ion-exchange method. Cobalt forms deep blue complexes CoCl4

2- in 9M HCl readily.

- The scheme for the separation of Co(II) and Ni(II) by ion-exchange method still follows the principle behind this experiment. This time, we will use the fact that Co(II) forms complexes with HCl at 9M concentration of the acid. So, what we are going to do is to increase the concentration of the HCl for the preparation of the sample. Based on my calculations, the aliquot should be added with around 75 mL of concentrated HCl (see cal. 5). The diagram for the separation is shown on the next page.

SEPARATION OF NICKEL(II) and COBALT(II)

Prepare a strong base anion exchange resin column.

Obtain 2 mL aliquot from the stock solution of unknown sample into a 100 mL volumetric flask.

Add 75 mL of concentrated HCl to the aliquot, and dilute the solution to mark with freshly distilled water.

Transfer 10 mL of the resulting solution into the column, and drain slowly, until the liquid level is nearly above the resin.

Rinse the column with portions of HCl. Place 250 mL conical flask beneath the column, drain the liquid level just above the resin each washing.

Elute the Co(II) with about 100 mL of water through the column, same flow rate. Collect all eluate in a 500 mL conical flask.

Elute Ni(II) with about 50 mL of HCl at a flow rate 2 -3 mL per minute, collecting all eluate to the 250 mL conical flask.

Add 10-20 mL of the Buffer solution to the eluate of Co(II).

Evaporate the excess HCl from the eluate of Ni(II) just to dryness and avoid overheating.

Dissolve the residue in about 100 mL of water and add 10-20 mL of the Buffer solution.

Add 1-2 drops of Eriochrome Black T indicator to the solution and titrate carefully with standard EDTA.

Add 15 drops bromopyrogallol or 0.2 g Murexide. Titrate carefully with standard EDTA.

VI. REFERENCES

Principles of Size-Exclusion Chromatography. (n.d.). Retrieved from http://www.separations.us.tosohbioscience.com/ServiceSupport/TechSupport/ResourceCenter/PrinciplesofChromatography/SizeExclusion

Principles of Ion-exchange Chromatography. (n.d.). Retrieved from http://www.separations.us.tosohbioscience.com/ServiceSupport/TechSupport/ResourceCenter/PrinciplesofChromatography/IonExchange

EDTA titration overview. (April 28, 2009) Retrieved from http://www.titrations.info/EDTA-titration

Ion-exchange Chromatography. (2010) Retrieved from http://www.sigmaaldrich.com/life-science/proteomics/protein-chromatography/ion-exchange-chromatography.html

Kevin Yip. .(1997). Chromatography. Retrieved from http://www.rpi.edu/dept/chem-eng/Biotech-Environ/CHROMO/chromintro.html

Complexometric titration. (June 2008). In Wikipedia, The Free Encyclopedia. Retrieved December 30, 2010, from http://en.wikipedia.org/wiki/Complexometric_titration

Chromatography. (27 December 2010). In Wikipedia, The Free Encyclopedia. Retrieved December 30, 2010, from http://en.wikipedia.org/wiki/Chromatography

VII. COMMENTS

This experiment so far is the most challenging one for us partners, since both of us were

assigned as class monitors for the whole duration of the experiment. During the first meeting,

my partner was tasked to prepare several solutions for the rest of the class, so I thought I would

be left alone to do our experiment. However, my partner is just so good that he still took time

to monitor, and give a bit of help on our activity. Fortunately, despite the endeavor during the

first meeting we still managed to reach the goal for the meeting.

The next meeting, it was I who was assigned to standardize the EDTA solution. With my

co-monitor, we did the job carefully, while I try to help my partner in doing the remaining part

of the experiment. Gladly, I hit two birds with one stone. I and my co-monitor successfully

standardized the EDTA solution, at the same time I and my laboratory partner just had our own

job well done.

To sum it all, consideration made the experiment a success for us both. If we had no

consideration while doing the experiment, we could not have done the laboratory work. So, I

would say that my partner just did a very good job in this experiment.

VIII. CALCULATIONS

Cal. 1 Standardization of EDTA Solution:

MEDTA=massCaCO3×%Purity

V EDTA×Molar MassCaCO3

×V Aliqout

V Stock Sol' n

Trial 1:

MEDTA=0.1316gCaCO3×99%

0.0267 LEDTA×100.0869gCaCO3

molCaCO3

×50mLAliqout

250mLStock Sol 'n

MEDTA=0 .009751M

Average Molarity EDTA:

MEDTA=0.009751M+0.009899M+0.009751M

3

MEDTA=0 .00980M

Cal. 2 Titrimetric Analysis of Nickel Using EDTA:

Ni2+ + (EDTA)4- → [Ni(EDTA)]2

Moles¿( II)=V EDTA×MEDTA100mL10mL

×100mL2.0mL

Our Group’s Result:

Moles¿( II)=1.90mLEDTA×0.00980mmolEDTAmLEDTA

×100mL10mL

×100mL2.0mL

Moles¿( II)=9 .31mmol¿(II )

Mass¿(II )=Moles¿(II)×Molar Mass¿(II)

Mass¿(II )=9.31mmol¿(II )×58.71mg∋(II )mmol∋(II )

Mass¿(II )=547mg∋(II )Cal. 3 Titrimetric Determination of Zinc using EDTA:

Zn2+ + (EDTA)4- → [Zn(EDTA)]2-

MolesZn(II)=V EDTA×MEDTA100mL10mL

×100mL2.0mL

Our Group’s Result:

MolesZn(II)=1.70mLEDTA×0.00980mmolEDTAmLEDTA

×100mL10mL

×100mL2.0mL

MolesZn(II)=8 .33mmolZn(II)

MassZn(II )=MolesZn(II )×Molar MassZn(II )

MassZn(II )=8.33mmolZn(II)×64.409mgZn(II )mmol Zn(II )

MassZn(II )=545mgZn (II )

Cal. 4 Test for Outliers: At 90% confidence interval

Q= gaprange

Qcal<Qtab (Accept)Qcal>Qtab (Reject)

Suspected outliers:

Trials 2 and 6 for the Mass of Ni (II)

Trial 3 for the Mass of Zn (II)

Trial 2 for the Mass of Ni (II):

Q90%=711−563711−284

Q90%=0 .400

0 .400<0 .560 (Accept)

Trial 6 for the Mass of Ni (II):

Q90%=313−284711−284

Q90%=0 .0667

0 .0667<0.560 (Accept)

Trial 3 for the Mass of Ni (II):

Q90%=824−634824−539

Q90%=0 .667

0 .0667>0.765 (Accept)

Cal. 5 Calculation of the volume of HCl needed for the preparation of sample of Ni(II) and Co(II).

M 1V 1=M2V 2

V 1=M 2V 2

M 1

V 1=9M× .1L12M

V 1=¿ 0.075 L