Part 4

Summary

In this lab experiment, conducted in a fume hood due to hazardous vapors, the reactions of Nickel(II) chloride with various ammonia solutions and hydrochloric acid are explored. The process begins with a clear, pale bluish-green Nickel(II) chloride solution, which becomes cloudy upon the addition of 1 M ammonia, indicating precipitate formation. Adding 15 M ammonia clears the solution, changing it to pale bluish violet. Finally, hydrochloric acid is added, causing the color to revert while producing toxic vapors. Proper chemical disposal is emphasized, ensuring safety throughout the experiment.

Takeaways

• 😀 The lab procedure is conducted in a fume hood to avoid inhaling harmful vapors.
• 😀 Start with a clean and dry test tube placed in a test tube holder.
• 😀 Use a 0.1 molar nickel(II) chloride solution for the experiment.
• 😀 Add between 2-3 mL of nickel(II) chloride solution to the test tube, which is clear with a pale greenish-blue color.
• 😀 Add 2-3 drops of 1 molar ammonia solution and observe slight cloudiness, indicating the formation of a precipitate.
• 😀 The cloudiness indicates that a precipitate is forming as ammonia reacts with nickel(II) chloride.
• 😀 Afterward, add 2-3 drops of a more concentrated 15 molar ammonia solution.
• 😀 The solution turns from pale green to a pale bluish-violet color and becomes clear, with no precipitate remaining.
• 😀 Finally, add several drops of 6 molar hydrochloric acid to the solution.
• 😀 After adding hydrochloric acid, the color shifts back to a pale violet color, and smoke may be observed above the solution, indicating the release of toxic vapors.
• 😀 Dispose of all chemicals properly according to your instructor’s instructions after the experiment.

Q & A

Why is it important to conduct this part of the lab in a fume hood?

It is important to conduct this part of the lab in a fume hood because hazardous vapors may be produced during the experiment, which can be harmful to breathe in.

What solutions are required for this lab procedure?

The solutions required for this lab procedure are 0.1 molar nickel(II) chloride solution, 1 molar ammonia solution, 15 molar ammonia solution, and 6 molar hydrochloric acid solution.

What is the initial color and clarity of the nickel(II) chloride solution?

The initial color of the nickel(II) chloride solution is pale green, and it is clear.

What observation is made after adding 1 molar ammonia solution to the nickel(II) chloride solution?

After adding the 1 molar ammonia solution, the solution turns slightly cloudy, indicating the formation of a precipitate.

What happens when 15 molar ammonia solution is added to the mixture?

When the 15 molar ammonia solution is added, the color changes from pale green to a pale bluish violet, and the solution becomes clear again, indicating that the precipitate has dissolved.

What is the final color of the solution after adding hydrochloric acid?

After adding hydrochloric acid, the color of the solution changes back to a pale violet.

What observation is made regarding the vapors after adding hydrochloric acid?

After adding hydrochloric acid, smoke can be seen above the solution, indicating the presence of toxic vapors.

What is the procedure for disposing of the chemicals used in the experiment?

The chemicals should be disposed of properly as directed by the instructor.

How many drops of the 1 molar ammonia solution were required for the cloudiness to appear?

Between two and three drops of the 1 molar ammonia solution were required, but it took about six or seven drops for cloudiness to appear in the speaker's experience.

Why is it critical to note the color changes during the experiment?

Noting the color changes during the experiment is critical as they indicate chemical reactions and the formation or dissolution of precipitates, which are important for understanding the chemical processes involved.