Lab Quiz

How accurate are the volumes measured with serological pipets. (Select all that apply.)

0.01 mL

When a student was weighing out a sample, the balance display read "0.500 g." Which of the following is the correct way to record this value into a lab notebook? (Select all that apply.)

0.500 g

In the video entitled "Using an Analytical Balance", Lindsey demonstrates weighing a solid into what on an analytical balance? (Select all that apply.)

An empty, clean and dry beaker.

When reading the meniscus of a volumetric flask, which of the following are acceptable? (Select all that apply.)

Bend down to view the etched line on the volumetric flask at eye-level. View the etched line on the volumetric flask at eye-level.

Before using a pipet, it should first be conditioned. Please select the step or steps that are involved in properly conditioning a pipet. (Select all that apply.)

Draw a small volume of reagent into the pipet, turn it sideways and rotate so all the walls are coated with reagent. Pour some reagent into a beaker for use with the pipet. Dispose of the reagent into a waste beaker since it is now contaminated with whatever may have been on the pipet.

Please view the video "Using a Volumetric Flask." After transferring all of the solid from a weighing beaker into a volumetric flask, which of the following describes the step or steps to finish making the solution? (Select all that apply.)

Fill the volumetric flask with a significant volume anywhere from about from half-way to where the neck narrows. Stopper the flask and invert a few times to ensure complete mixing and that the solid is completely dissolved. Once the solid is dissolved, fill the volumetric flask almost to the etched line and finish adding solvent dropwise until the bottom of the meniscus is touching the etched line.

In the video entitled "Using a Volumetric Flask", Lindsey demonstrates a quantitative transfer. Which of the following practices are important to achieve a quantitative transfer when adding a solid to a volumetric flask? (Select all that apply.)

Gently tap on the paper funnel so that no solid is left clinging to it. Rinse the weighing beaker with deionized water or the solvent being used, and add it to the volumetric flask. Make sure that no solid is spilled when pouring it from the weighing beaker through the paper funnel.

When using a volumetric flask, which of the following are true? (Select all that apply.)

If the solid is added to a volumetric flask after filling it with solvent, the concentration of the resulting solution will be lower than the calculated value. If a volumetric flask is over-filled so that the bottom of the meniscus is above the etched calibration mark, the concentration of the resulting solution will be lower than the calculated value. If any solute is lost in transfer, the concentration of the resulting solution will be lower than the calculated value. If a volumetric flask is filled so that the top of the meniscus is level with the etched calibration mark, the concentration of the resulting solution will be higher than the calculated value.

When using a syringe pump with a volumetric pipet, which of the following are true? (Select all that apply.)

Solution should be drawn up such that the bottom of the meniscus aligns with the calibration mark. Once the appropriate amount of solution is in pipet, the release should be pressed when the pipet is above the volumetric flask or desired receptacle. The syringe pump should be firmly connected to the end of the pipet in order to make a seal.

In the video entitled "Using an Analytical Balance", what does Lindsey recommend you use to clean the weighing pan before and after use? (Select all that apply.)

The brush that is provided.

If you significantly overshoot your target weight on an analytical balance, which of the following actions are correct? (Select all that apply.)

The excess material should be considered waste and disposed of properly. You should use the spatula provided to remove excess material.

Regarding the solution that remains in a pipet after gravity has drained it, which of the following are true? (Select all that apply.)

The remaining solution in a volumetric pipet should NOT be gently expelled with a pipet bulb to complete the transfer. The remaining solution in a serological pipet should be gently expelled with a pipet bulb to complete the transfer.

In the video entitled "Pipeting Techniques Using Syringe Pump", the presenter demonstrates the proper use of which of the following? (Select all that apply.)

Volumetric pipets Serological pipets

Once the reading on the analytical balance stops fluctuating, which of the following are true? (Select all that apply.)

You should record the mass in your lab notebook with a pen.