Laboratory Procedures for Iron(II) Salt and Crucible Preparation

Preparation Steps for Lab Experiment

Choosing the Initial Step

  • Depending on the availability of a mass meter, start with either Step a or Step b.

Step A: Measuring Iron(II) Salt

  • Measure approximately 0.4 ext{ g} of the supplied iron(II) salt.
    • Use a 250 cm³ beaker for this measurement.
    • If the mass of the beaker exceeds the maximum capacity of the mass meter, utilize a watch glass instead.
  • Record the measured mass in the answer book.

Step B: Preparing the Crucible

  • In scenarios where all mass meters are occupied, prepare the crucible instead.

Crucible Preparation Procedure:

  1. Check Crucible Condition
    • Ensure the crucible is clean and free from cracks.
  2. Heating the Crucible
    • Heat the crucible strongly using a soot less flame for about one minute.
    • After heating, allow the crucible to cool on a tripod.
    • If black soot marks are present inside the crucible, reheat it strongly until all soot is incinerated.
    • This step is crucial to ensuring that all unwanted materials that can be incinerated are removed from the crucible.

Tips for Efficient Heating

  • The experimental time can be significantly reduced by optimally using the Bunsen burner:
    • Turn the gas supply to the Bunsen burner to maximum flow rate.
    • Adjust the air supply located at the base of the burner.
      • Flame Characteristics:
      • When air supply is low:
        • The flame appears long and yellow, indicating incomplete combustion, which leads to soot deposition.
      • When air supply is increased:
        • The flame shortens and turns light blue with a slight hissing sound, indicating complete combustion.
    • Flame Structure:
      • The flame has two regions:
      • Inner Cone:
        • Represents incomplete combustion.
        • Results in soot deposition.
      • Outer Cone:
        • Represents complete combustion.
        • No soot is deposited.
        • Achieves the highest temperature at the middle of this outer conical region.
    • Above the outer cone, cold air mixes with the flame, leading to a quick drop in temperature.