CH202 Lab Quiz 3

When reading the meniscus of a volumetric flask, which of the following are acceptable? -Bend down to view the etched line on the volumetric flask at eye-level. -View the etched line on the volumetric flask below your eye-level. -View the etched line on the volumetric flask above your eye-level. -It does not matter where the etched line is on the volumetric flask in relation to your eye-level. -View the etched line on the volumetric flask at eye-level.

-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. -Drain the reagent back into your beaker so it can be used again. -Pipet directly from the reagent bottle. -Draw enough reagent into the pipet to fill it above the etched mark so that all of the walls are coated with reagent. -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.

-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.

When using a volumetric flask, which of the following are true? -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 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 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 higher than the calculated value. -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 any solute is lost in transfer, the concentration of the resulting solution will be higher than the calculated value. -If the solid is added to a volumetric flask after filling it with solvent, the concentration of the resulting solution will be higher 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 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.

-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 over-filled so that the bottom of the meniscus is above the etched calibration mark, the concentration of the -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 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? -If the pipet is over-filled with too much solution, the roller should be rolled up with the tip of the pipet outside the fill solution. -Solution should be drawn up into the entire pipet to the top. -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. -The syringe pump should be loosely connected to the end of the pipet so that it easily falls off. -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. -Solution should be drawn up such that the bottom of the meniscus aligns with the calibration mark.

which of the following practices are important to achieve a quantitative transfer when adding a solid to a volumetric flask -Rinse the weighing beaker with deionized water or the solvent being used, and add it to the volumetric flask. -Rinse the paper funnel with deionized water or the solvent being used into the volumetric flask. -Rinse the weighing beaker with deionized water or the solvent being used, and dispose of it in the waste bottle. -Gently tap on the paper funnel so that no solid is left clinging to it. -Make sure that no solid is spilled when pouring it from the weighing beaker through the paper funnel.

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

If you significantly overshoot your target weight on an analytical balance, which of the following actions are correct? -The excess material should be returned to the reagent jar. -The excess material should be kept on weighing paper and used for the next sample that must be prepared. -The excess material should be considered waste and disposed of properly. -You should lift up the beaker, and gently tap it to pour the excess material back into the reagent jar. -You should use the spatula provided to remove excess material.

-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? -The remaining solution in a serological pipet should NOT be gently expelled with a pipet bulb to complete the transfer. -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 volumetric pipet should be gently expelled with a pipet bulb to complete the transfer when using the scale that ends at zero on the pipet tip. -The remaining solution in a serological pipet should be gently expelled with a pipet bulb to complete the transfer.

-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.

How accurate are the volumes measured with a serological pipet?

0.01 mL

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? -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. -Fill the volumetric flask all the way to the etched line, stopper it 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 top of the meniscus is touching the etched line.

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.

the presenter demonstrates the proper use of which of the following? Serological pipets Volumetric pipets Burets Measuring pipets Volumetric flasks Mohr pipets

Serological and Volumetric pipets

hat does Lindsey recommend you use to clean the weighing pan before and after use?

The brush that is provided

Lindsey demonstrates weighing a solid into what on an analytical balance?

an empty, clean and dry beaker