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Lab 16: Identification of Anions and Cations

Abstract: This investigation determined the ions in an unknown solution through the

application of chemical tests.

aime Lope!

"ctober ##nd$ #%11 Lab &artner: ason 'uang

Introduction: (e conducted laborator) anal)sis to determine the ionic composition of an

unknown solution. In effect$ we are chemical detectives. These tests are called *ualitiveanal)sis. (e became$ in effect$ chemical detectives. The tests we ran are solutions of


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unknown ions$ which were sub+ected to man) tests$ such as burning$ and then an

anal)!ation of the b)products such as gas$ color change$ and formation of water droplets.

A comparison test was then done with a known ionic solution. These tests are accuratedue to the fact that no two ions have the e,act same reaction to chemicals.

&rocedure: The lab was split into two da)s. "n the first da)$ we first set water to heat up.(e then tested each individual ion compared to our unknown. -or the first da)$ we

t)picall) added twent) or so drops of the known and unknown into two separate test

tubes. Then$ we added a reactant$ such as nitric or h)drochloric acid$ to get a reactionfrom both products. -or &"/0$ we also added a water bath to heat the solutions inside the

test tube for five minutes or so. Then we let them cool$ and we observed.

"n da) two$ we preformed much the same tests$ adding the known and unknown

solutions into two separate tests tubes$ and then adding acid. 'owever$ in one instance$after burning a solution$ we used litmus paper to get a color change$ careful not to touch

the sides and we also preformed additional water baths.

ata and "bservations:

Ion TestReagents/TestProcedure

Test Results forSolutions withIon

Test Results forUnknownSolution #9

Is Ion Presentin Unknown?

Cl- HNO3 , AgNO3 White, cloudy Yellow,cloudy,formation ofsolid

No

So-2 !" HCl #Acid$,%aCl

White, cloudy &ee' yellow No

HCO-3 HCl #Acid$ %u((led,

ri''led

)i''led No

*O-3 HNo3, ##NH$2"oO

Clear solid,color changeto yellow

)emainedsame color#yellow$

No

+e3 ##H2$S$3,.SCN

%lac/ishsu(stance

%lac/ishsu(stance,#'ossi(leyellow solid,'ossi(lyim'ro'ercleaning$

Yes

Na Wet 0-1i' Yellow coloredame

Horri(lesmell, same

ame asoriginal

No

. . *in/ishsalmon coloredame

%ad smell,same ameas original

No

Ca2 Na2C2O +oggy, clear Yellow-orange No

NH NaOH Slight (lue Slight (lue Yes


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I noticed that man) of the solutions had slight differences onl) when the) reacted.

'owever theses differences meant that the) could not be the same compound$ because

the) had to be e,actl) alike in order to be considered the same solution.

Identification of 2nknown: -rom our e,periments$ we were able to determine that ourcompound formula was 34'05-e and the name of our compound is Ammonium Iron ion.

Anal)sis: (e received this conclusion after we matched the colors of the products afterthe) were sub+ected to tests. In each case$ the) had the e,act same reaction$ which is onl)

possible if the) are the e,act same ion. The) onl) possible reason for an incorrect ion

would be the possible )ellow substance present in the anion$ -e$ although its possible

that the test tube was improperl) cleaned$ which is our own error.

Conclusion: In conclusion$ we attempted to and succeeded in$ identif)ing anions and

cations$ and then naming the compound that was formed as a result. (e learned how now

that careful observation is important in getting a correct result$ and that some chemicalreactions are not permanent and ma) change rapidl)$ thus causing an incorrect test result.

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