CHM 230 Lab Exam 2 KSU

If Cl- and SO42- are present, what cannot be present?

Pb2+

What confirms the presence of Calcium?

Red flame

color of Fe3+

brownish yellow

What is the only anion that will precipitate with barium?

Sulfate (SO4)2-

What confirms the presence of Fe3+

A deep blue colored solution

color of Ni2

Very pale green

What confirms the presence of Zn2+?

a pale blue precipitate

requirements for spontaneous reaction

-positive E-cell value

-standard conditions

What 2 complex ions form after addition of ammonium buffer?

Zn(OH)4^2- and Ni(NH3)6^2+

cathode

an electrode at which reduction occurs

What precipitates form after addition of the ammonium buffer?

Fe(OH)3 and Cr(OH)3

What is added to solution to test for nitrate?

NH3

What confirms the presence of Cr3+

A yellow precipitate

What confirms the presence of ammonium ion?

Red litmus paper turns blue

Anode

the electrode at which oxidation occurs

amphoteric

soluble in acid and base

What confirms the presence of Ni2+

Red precipitate

What confirms the presence of K+

Purple flame

color of Cr3+

grayish blue

What confirms the presence of Pb2+

Heavy black precipitate

What anion is confirmed when precipitate dissolves in NH3?

Cl-

What is confirmed during the brown ring test?

NO3-

Separation and Identification of SO4 (anion)

Ba^2+ + SO4 ^2- = BaSO4 (s).

Precipitate remains, SO4 is present

Identification of Cl- (anion)

AgCl(s) + 2NH3(aq) --> Ag(NH3)2 + Cl- (aq). Precipitate dissolves, Cl- is present

Test for NO3- (anion)

Brown ring test. Brown ring confirms NO3-

Lavender flame

K+

Red flame

Calcium is most likely present

1. Confirmation of NH4+

NH4 +OH- ---> NH3 + H2O

If NH3 is present, litmus paper should turn blue.

2. Separation of Pb^2+

Pb + 2Cl- --> PbCl2 (precipitate)

Use ice bath to separate

3. Confirmation of Pb^2+

PbCl2 ---> Pb + 2Cl-

Heavy black precipitate confirms Pb ^2+

4. Separation of Fe^3+ and Cr ^3+

pH must be between 8-9.

Ca must not be allowed to form Ca(OH)2

6. Confirmation of Fe^3+

Deep blue color confirms presence of Fe3+

7. Confirmation of Cr^3+

Yellow precipitate confirms presence of Cr3+.

White Precipitate confirms NO Cr ions

Pb + CrO4 --> PbCrO4

8. Separation and Confirmation of Ca^2+

White precipitate suggests the presence of Ca^2+

Brick red flame confirms Ca^2+

9. Separation of Nickel and zinc

Precipitate may be blue or white

When heating the white one, it will turn blue

Blue coloration confirms the presence of Zn^2+

10. Confirmation of Nickel

Red precipitate confirms the presence of Ni^2+ ions.