Question

iron(iii) thiocyanate spectroscopy
dilution process
the student creates 100.00 ml of each of
the dilute solutions from the concentrated
stock solution. below is a list of the steps
involved in the dilution process.

step 1: obtain a 100.00 ml volumetric
flask.

step 2: measure out 60 ml of 0.1000 m
fescn²⁺ using a beaker.

step 3: use a funnel to pour
the fescn²⁺ into the volumetric flask.

step 4: add distilled water to the fill line. cover
and allow the solution to mix.

which step in the dilution process is not
correct and why?

step 4: the distilled water should be measured
using a beaker.

step 2: you should use a graduated cylinder or
pipette for measuring the stock solution.

step 3: exactly 40.0 ml of water should be placed
into the volumetric flask first.

step 1: you should use a graduated cylinder for the
dilution.

Explanation:

1. For preparing precise dilutions to a fixed volume (100.00 mL), accurate measurement of the stock solution is critical. A beaker is not designed for precise volume measurement; graduated cylinders or pipettes are the correct tools for this step.
2. Analyzing other options: Step 1 is correct (volumetric flasks are for fixed-volume dilutions). Step 3 is incorrect logic (water does not need to be added first, and the volume is not fixed at 40 mL). Step 4 is incorrect logic (distilled water is added to the calibration mark, not measured in advance with a beaker).

Answer:

Step 2: You should use a graduated cylinder or pipette for measuring the stock solution.