Practicals: Salt Analysis

Question 1

What is the observation and inference when ammonium hydroxide is added to the salt/solution?

Answer 1

Observation: white precipitate

Inference: K+ is present.

Question 2

Solution/salt + sodium cobalt nitrite [Na3Co(NO2)]. State the observations, inference.

Answer 2

Observation: yellow precipitate

Inference: K+ is present

KCl + Na₃Co(NO₂)₆ ==> K₃[Co(NO₂)₆] + NaCl

Where K3[Co(NO2)6] is the yellow precipitate.

Question 3

Salt/solution + ammonia solution (NH3); write the observation, inference, and equation.

Answer 3

Observation: white precipitate.

Inference: Al3+ is present; aluminium hydroxide is formed.

AlCl3 + 3NH4OH ==> Al(OH)3 + 3NH4Cl

Where Al(OH)3 is the white precipitate.

Question 4

Precipitate from adding ammonia solution to salt/solution + HCl. State the observation, inference, and reaction.

Answer 4

Observation: soluble in HCl, colourless solution.

Inference: AlCl3 is formed

Al(OH)3 + 3HCl ==> AlCl3 + 3H2O

Where AlCl3 is soluble

Question 5

Solution/salt (not precipitate now) + acetic acid (CH3COOH).

Answer 5

Observation: white precipitate.

Inference: Al3+ is present.

Question 6

Salt/solution + HNO3 + AgNO3

Answer 6

Observation: white precipitate.

Inference: Cl- is present.

Cl^-_(aq) + AgNO3_(aq) ==> AgCl_(s) + NO^-₃

Where AgCl is the white precipitate 🐻‍❄️

Question 7

State three precautions to ensure accurate results in titration.

Answer 7

1. I rinsed the burette with a small amount of acid.
2. I rinsed the conical flask with distilled water.
3. I ensured there were no air bubbles in the burette and pipette.
4. I read off the burette at eye level.