Exam 3: Tools of the Trade

A 0.1500 M HCl solution was prepared on a day when the temperature was 20^oC.What is concentration of the solution when used the next day at 27^oC? The density of water is 0.9982071 g/mL at 20^oC and 0.9965162 g/mL at 27^oC.

A student titrated extracted chloride from a soil sample with 0.1 M silver nitrate.During the titration he performed the following actions while operating the buret. -Washed the buret with silver nitrate solution -Drained titrant slowly -Delivered a fraction of a drop near end point -Read bottom of concave meniscus -Avoided parallax -Accounted for graduation thickness in readings His instructor notes on the student's lab report that the student forgot to____________________ when operating his buret.

____________________ is the liquid from which a substance precipitates or crystallizes.

Which of the following is NOT a good practice when keeping a laboratory notebook?

Which of the following statements are TRUE? I Organic solvents,concentrated acids,and concentrated ammonia should be handled in a fume hood. II A respirator should be worn when handling organic solvents. III All containers should be labeled to indicate what they contain. IV Contact lenses are adequate to protect eyes from liquids and gases in the lab.

____________________ is a set of principles intended to help sustain a habitable planet.

Which scenario below has the lowest relative uncertainty?

A researcher dispenses distilled deionized water from a 20-mL volumetric pipet into an empty 8.4376 g weighting bottle.If the total mass of water and weighting bottle is 28.5845 g,what is the volume of the water delivered by the 20-mL pipet? The density of water is 0.9967867 g/mL. A)20.21 mL B)20.08 mL C)28.68 mL D)19.94 mL E)19.90 mL

The mass of the empty receiving vessel used with an analytical balance is the:

____________________ is used to convert a precipitate to a known,constant composition.

The____________________ fulfills the critical function of reporting what a researcher has done and what they observed,and allows another researcher to repeat their work.

On a lab quiz,a student listed the steps to properly use a pipet.Which step is incorrect?

____________________ are calibrated to deliver one fixed volume and are____________________ than________________________________________.

Which of the following is FALSE regarding volumetric flasks?

A student prepares a solution using a 1 L volumetric flask.When he finishes,the meniscus is above the calibration mark on the flask neck.The concentration of the solution is:

Which of the responses below are sources of weighing error? I Weighing a sample that is warmer than ambient temperature. II Cooling a sample in a desiccator prior to weighing. III Periodically calibrating the balance. IV The temperature of the balance changing over time.

Drying to constant mass is a common gravimetric analysis technique.Which of the statements describe the source of false weights? I A warm crucible II Touching the crucible with bare fingers III Using a microwave oven to dry reagents and crucibles IV Using a desiccator

Which of the statements below is(are)TRUE regarding collecting and storing samples for trace analysis? I Trace ionic analytes stored in glass are lost by adsorption or contaminated by metals leaching from the glass surface. II Plastic bottles are recommended to collect and store ionic analyte samples. III Amber glass bottles are best for collecting and storing aqueous samples of organic materials.

____________________ is the upward force exerted on an object in a gaseous or liquid fluid.The mass measured by an analytical balance in air is____________________ its actual mass.