Question

Difficulty: EasyProcedural Steps

Preparing a standard solution of a specific molarity requires a series of precise laboratory steps to ensure accuracy. First, the technician accurately weighs the solid solute on an analytical balance. The weighed solute is then transferred into a clean beaker, where a small volume of distilled water is added. The mixture is stirred gently with a glass rod until the solid is completely dissolved. Following dissolution, the liquid is carefully poured through a funnel into a volumetric flask of the desired volume. To guarantee that no solute is left behind, the beaker and glass rod must be rinsed multiple times with distilled water, and these washings must be added directly to the flask. Next, the technician adds distilled water to the flask until the level approaches the graduation mark on the neck. Using a Pasteur pipette, water is added dropwise until the bottom of the meniscus is exactly aligned with the mark. Finally, the flask is stoppered and inverted several times to ensure the solution is thoroughly mixed and homogeneous. Skipping the rinsing step, or failing to add the rinsings to the flask, will result in an inaccurate, lower concentration than intended.

According to the passage, what is the direct consequence of failing to rinse the beaker and add the washings to the volumetric flask?

  1. A
    The solid solute will not dissolve completely when water is added.
  2. The final concentration of the standard solution will be lower than intended.Answer
  3. C
    The bottom of the meniscus will fail to align with the graduation mark.
  4. D
    The solution will remain unmixed and non-homogeneous after inversion.

Answer

The final concentration of the standard solution will be lower than intended.
The correct answer is correct because the final sentence of the passage states that skipping the rinsing step, or failing to add the rinsings to the flask, will result in a lower concentration than intended. Rinsing ensures all solute is transferred into the volumetric flask.

Step-by-Step Solution

1
Locate the portion of the passage describing the rinsing step and its purpose.
The text states that the beaker and glass rod must be rinsed to guarantee no solute is left behind, and the washings must be added to the flask.
This establishes the procedural purpose of the rinsing step.
2
Locate the sentence addressing the consequence of skipping this step.
The final sentence explicitly states that skipping the rinsing step, or failing to add the rinsings, will result in a lower concentration than intended.
This directly answers the question about the consequence of omitting the step.
3
Evaluate the choices to find the one matching the identified consequence.
The option stating the final concentration will be lower than intended matches the text directly.
This ensures the correct option is selected based on literal comprehension of the sequence.

Key Concept

Identifying the consequences of omitting a specific step in a described laboratory procedure.
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