General unknown lab report PDF

Preview

Summary

It is the General unknown lab report. It is a kind of informal lab report. We had to find ions in the unknown and known solutions. the ions that were present in the unknown areFe3+, Ni2+, Co2+, Cr2+, and the ions present in known are Al3+, Mn2+ Ca2+, Mg2+, Ag+, Cr3+, Ni2+, Cu2+, Co2+, Fe3+, Ba2+....

Description

Chem 201, Section 10 11/17/21

General Unknown Lab Report Unknown #: 44288 Known: Al³⁺, Mn²⁺ Ca²⁺, Mg²⁺, Ag⁺, Cr³⁺, Ni²⁺, Cu²⁺, Co²⁺, Fe³⁺, Ba²⁺

Results: Ions Present

Ions Absent

Fe³⁺

Al³⁺

Ni²⁺

Mn²⁺

Co²⁺

Ca²⁺

Cr²⁺

Mg²⁺ Ag⁺ Ba²⁺ Cu²⁺

Discussion: Fe³⁺:

For the detection of iron, I started with the precipitate from step 2h which was a

light brown color. I then added 20 drops of 2 M sulfuric acid and boiled gently, which turned the solution a green color. Then, I added a drop of 6% H2O2 and the precipitate dissolved. Then I added one drop of 0.2 M potassium thiocyanate turning the solution blood-red instantly, proving the presence of iron.

Fe³⁺ (aq) + KSCN (aq) → Fe(SCN)₆³⁻ (aq) + K⁺(aq)

Co2+:

Originally in the experiment, I detected no presence of the cobalt ion. However, the

spot test proved the presence of cobalt. I added 15 drops of NH4SCN in 50% alcohol to the solution. The solution turned purple showing both cobalt and iron were present. To further determine if cobalt was present, I added NaF(s) until the red color of iron disappeared leaving a teal blue solution proving the presence of the cobalt ion. Co2+(aq) + 4SCN-(aq) →Co(SCN)42- (aq)

Ni²⁺:

With my unknown sample, I added 6 M NH3 (aq) until the solution was alkaline.

The solution then turned blue and no precipitate formed for me to decant. Then I added 4 drops of dimethylglyoxime. Upon addition, a strawberry red precipitate formed proving the presence of Ni²⁺. 2(CH3)2C2N2O2H2 (aq) + Ni2+(aq) → H2O (l) + Ni[(CH3)2C2N2O2H]2 (s)

Cr3+:

To the supernatant of step 3c of the experiment, I added 7 drops of

0.2 M barium chloride. No precipitate formed at this step, remaining a white cloudy mixture. Since no precipitate formed, I skipped to step 3g. I added 3 drops of 3 M nitric acid to the solution and heated it while stirring. No yellow or orange color formed in the solution. I then proceeded to add 10 drops of cold DI water then 10 drops of ether after letting it cool. I also added 1 drop of 6% H2O2 . After mixing and allowing it to settle, a blue color formed in the upper layer of the solution, proving the presence of chromium. Cr2O72- (aq) + 4H2O2 (aq) + 2H+(aq) → 2CrO(O2)2 + 5 H2O (l)...