ch 202

volumetricpipet

only has one possible volume - excess drop should not be expelled

Volumes obtained with volumetric flasks, pipettes, and burets are recorded to the nearest _____________ mL.

.01

Burets, pipets, and small volumetric flasks are accurate to about

0.01 mL

How accurate are the volumes measured with a serological pipet? (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

beers law formula

A = ε l c

definition of ε

D. molar absorptivity, a constant unique to that substance at that wavelength

what actions should you take if you spill the mixing lab chemicals on you

First, flush the affected area with water. Next, have your lab partner notify your instructor about the spill.

What actions should you take if you spill copper(II) sulfate solution on yourself?

Flush the affected area with water.

(c) If any of the solids in this experiment come into contact with your skin or clothing, what is the first thing to do?

Gently brush the solid off with a paper towel.

What solvent is used for this experiment? freezing point depression

Stearic acid

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.

a) If the spectrometer had been set to a different wavelength to measure absorbances (one where the copper would have absorbed more or less light), how would that have changed the results?

The results would have been the same.

(c) How would the results have changed if a cell with a different pathlength had been used for measuring the unknown than the calibration standards?

There is not enough information to determine how this would have changed the calculated unknown concentration, but it would not be the same. Correct: Your answer is correct.

what should you do if you splash a hazardous chemical in your eyes

Use the eyewash immediately. Hold your eyes open while flushing them with water. Have your lab partner notify your instructor about the accident.

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.

Proper attire for lab includes which of the following? (Select all that apply. See the Lab Safety section in Lab Safety and Practices in the Lab Manual.)

a shirt and pants that overlap about 6" in the middle to cover the torso shoes that cover the heels and toes pants that extend to the ankles a shirt that covers the shoulders and extends about 6" below the waist

definition of A

absorbance measured by the spectrometer

Which of the following chemicals are listed as hazardous? for the calerimitry lab

ammonia phosphoricacid

sodium persulfate It is listed as

an oxidizing agent

Oxidation occurs at the

anode

in redox electrons travelfrom

anode to cathode

In the lab, a student must wear safety glasses or goggles...

at all times

reduction occurs in the

cathode

0.1 M AgNO3 hazards

causes dark spots if spilled on skin toxic if ingested

definition of c

concentration, in mol/L, of the sample solution being measured

3.0 M NaOH hazards

corrosive

3.0 M HCl hazards

corrosive, irritating vapors

Most pipettes are built to __________________________ a known volume of liquid.

deliver

Which of the following is not a colligative property? boiling point elevation freezing point depression vapor pressure lowering density enhancement osmotic pressure

density enhancment

serological pipet

different values, a bulb is needed

This question deals with the wastes generated in the calorimetry lab. (a) The waste solutions should be ________________________________. . (b) The metal samples should be ____________________________

flushed down the sink with water returned to the containers on the side shelf

some of the chemicals in the buffers experiment are

hazards

which two titrations chemicals are corrosive

hydrochloric acid and sodium hydroxide

the sillute in part 2 ofthe freezing point depression experiment is

lauric acid

which two titration chemicals have no listed hazards

methyl orange phenolphthalein

Molar solubility has units of

mol/L

ascorbic acid (solid) hazards

none

graphite rods hazards

none

Stearic and lauric acids are ___________________ but prolonged contact with skin may cause irritation

nonhazardous

definition of l

pathlength of light through the cell

Which of the chemicals is corrosive? (Select all that apply.) - calorimitry

phosphoric acid

Stearic and lauric acids wastes should be

placed in the labeled waste container

which titration chemicals are irritants

potassium hydrogen phthalate sodium carbonate

It is good practice to "condition" a pipet before using it by

rinsing it with a few milliliters of the solution that will be pipetted.

When a sparingly soluble solid is in contact with solution, the solution is called

saturated

When working with a volumetric pipet, one adjusts the liquid level

so the bottom of the meniscus is at the scribed line on the pipet.

which titrations chemical is toxic

sodium carbonate

The only hazardous chemical listed in this experiment is

sodium persulfate

Ksp is the symbol for the

solubility product constant

sodium persulfate It is listed as an oxidizing agent, which can

supply its own oxygen and react violently

(a) The wastes in the Solubility Product Constant experiment should be disposed of in

the labeled container

Volumetric flasks are built _______________________ a known volume of liquid to an accuracy of about ________________ % of the flask's capacity.

to contain, .1

.1 M Cu(NO3)2 hazards

toxic if ingested

(a) Which hazards are associated with copper(II) sulfate?

toxic, irratant

In the Laboratory Safety Video, found in the Instructional Videos section of the Lab Manual, the Teaching Assistant demonstrated the following...

use of the emergency eye wash. use of the safety shower. proper lab attire. use of the emergency drench hose.

(a) What are the standard ways to make a solution of known concentration? (Select all that apply.)

Dissolve a weighed amount (known mass) of solid into a known volume of liquid. Dilute a known volume of stock solution into a known volume of liquid.

When one of the ions produced by a sparingly soluble solid is present in solution from another source, the common ion effect predicts that the ______________ will decrease

molar solubility

When draining the volumetric pipet,

one allows the liquid to flow out with gravity, then touches the pipet tip to receiving vessel to remove the last drop.

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.

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.

Which chemicals are listed as hazardous? in buffers

HCl HC2H3O2 NaOH

When operating the centrifuge, students should do which of the following?

Make sure that the lid is completely shut and the safety knob is turned to engage the safety switch. Centrifuge for approximately 30 seconds.

(a) When placing test tubes in the centrifuge, what are the best practices?

Place test tubes containing approximately equal volumes in opposite positions on the rotor. Never put stoppers or other items in the centrifuge with your tubes.

b) Which of the following are hazardous properties of potassium iodate, KIO3, and copper iodate, Cu(IO3)2? (Select all that apply.) solubility

They're strong oxidizing agents.

When the centrifuge process is complete, students should do which of the following?

Using the eyehole on top, monitor the spinning rate and open the lid only after the rotor has slowed significantly. Wait for the rotor to come to a complete stop before attempting to remove your test tubes.

When working with a buret, one should take care that

the tube below the stopcock is completely filled. the buret is conditioned by rinsing it with titrant before use. the last drop of liquid on the tip is flushed into the analyte.

A buret should be conditioned, then filled

to slightly below the top scribe mark (0.00 mL).

an absorbtivity equation has what units for x and y

x = concentration y = absorption

For which reaction are we trying to find the rate law? in kinetics experiment

2 I− + S2O82- → I2 + 2 SO42-

Select the statements that are correct with respect to waste disposal in the Electrochemical Cells Experiment. (Select all that apply.)

Dilute copper and ascorbic acid solutions should be disposed of in the waste container in the hood. Metal and graphite electrodes should be rinsed with water, dried, and returned to their positions on the lab bench The contents of the half-cell module should be disposed of in the waste container in the hood.

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.)

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

Which chemicals are listed as hazardous? in mixing lab

HCl NaOH

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

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 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 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.

What should be done to waste solutions containing copper ion? (Select all that apply.)

It should be disposed of in the bottle for waste copper ion when work is completed. It should be dumped in a beaker labeled "waste copper" on one's bench during the experiment.

(b) Which of the following are hazardous properties of sodium thiocyanate?

It's an irritant It's toxic.

(a) Which of the following are hazardous properties of nitric acid?

It's an oxidant. It's corrosive.

a) Which of the following are hazardous properties of copper nitrate, Cu(NO3)2? (Select all that apply.) solubility

It's corrosive. It's an oxidizer.

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.)

Make sure that no solid is spilled when pouring it from the weighing beaker through the paper funnel. 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.

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

Once there is solution in the pipet, the bulb should be replaced with a thumb or index finger so liquid can be slowly released to the desired level. The bulb should be held just firmly enough to the end of the pipet to make a seal. Solution should be drawn up only slightly above the calibration mark.

(b) In this experiment, you used a 1 cm pathlength cell for all measurements. If a 0.1 cm pathlength cell had been used for all the measurements, how would that have changed the results (concentration of the unknown)?

The calculated unknown concentration should be the same.

what happens if anode and cathode are swtched

The direction of current flow through the meter is reversed, and the sign of the voltage reading changes.

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.

) What actions should be taken if you spill a corrosive chemical on your skin? (Select all that apply.)

The first thing I should do is flush the area with water. I should have my lab partner report the incident to the instructor.

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 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.

What should be done with the wastes generated in this experiment? (Select all that apply.) for mixing labs - justs acids so

They can all be flushed down the sink with water.

what should be done with the buffer experment wastes

They can all be flushed down the sink with water.

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

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.

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

Volumetric pipets Serological pipets

which chemical in titrations lab can be flushed down the sink

all of them

(b) Which of the chemicals is a respiratory hazard with vapors that should not be inhaled? (Select all that apply.) - calorimitry

ammonia

To decrease the detection limit of copper ions in solution, ________________ will be added to form Cu(NH3)42+, a complex ion.

ammonia

an oxidizing agent such as sodium persulfate in a _________________________ can be handled safely

dilute concentration

The wastes in the Determination of an Equilibrium Constant Experiment should be

disposed of in the labeled container.