Chem 116 Lab
Calculate the theoretical yield of aspirin given that 0.909-g of salicylic acid was reacted with excess acetic anhydride.
1.19
Carey is using a lead cylinder as a counter weight. He would like to know the mass of the cylinder, but does not have a balance available. Knowing that his cylinder displaced a volume of 9.91 mL and that the density of lead is known to be 11.34 g/mL, what is the mass of his cylinder?
111.98
If a reaction evolves 606.83-J of heat as 0.021-moles of water are produced, what is the \Delta H of this reaction (in kJ/mol)? Report your answer to 2 decimal places.
28.9
How many mL of 0.01-M NaOH will be required to titrate 0.061-g of KHP to it's endpoint?
29.902
What is the ratio of citric acid (HCit) and sodium hydroxide (NaOH) based on the balanced chemical equation?
3 NaOH: 1 HCit
Report the volume of liquid contained in the graduated cylinder to the correct number of decimal places. DO NOT include units in your answer.
3.09
Why is the addition of the bicarbonate solution necessary when making the flavoring esters?
It is added to react with excess acetic acid so the acid doesn't mask the smell of the ester.
he following reaction can BEST be described by which of the following categories? BaCl2(aq) + H2SO4(aq) → BaSO4(s) + 2HCl(aq)
precipitation
What is the molar mass of KHP
204 g/mol
What is the MINIMUM temperature change that is acceptable to record in your manual?
4 degrees C
Jack and Jill are lab partners. Jill delivered 6.75 mL of a 20.96 % sugar stock solution using a graduated pipette into a 25-mL volumetric flask. Distilled water was added to the graduation mark on the flask and mixed well. What was the final concentration of the resulting solution?
5.66
Which of the following pH's is most reasonable for a titration of a strong base and weak acid that uses phenolphthalein as an endpoint.
9
Which of the following is a specific safety precaution that you must take this week?
All of these are specific safety precautions that you must take this week.
Adding the bicarbonate solution to the organic acid should result in which of the following noticeable changes?
evolution of gas
How much heat (in J) is evolved when two solutions are mixed together to give 38.91-g of solution and a temperature change of -5 degrees Celsius?
-814.0
To how many decimal places should the volume on the buret be read (hint: it is graduated the same way that the Mohr pipet is)?
2
AgNO3(s) → Ag(s) + NO2(g) + O2(g)
2,2,2,1
Which of the following scenarios was NOT mentioned as a possible troubleshooting point in the technique video?
Crushing the tablet with a mortar and pestle is difficult.
Review the following image and report what insoluble compound is likely leading to the opaque nature of the solution following the initial addition of aqueous ammonia.
Cu(OH)2
According to your lab manual, which of the following experimental steps MUST be carried out in the fume hood because of the risk of bumping.?
Heating the precipitate from Exercise 1 in acetone.
Which of the following statements best describes the proper disposal of the microcolumn?
In the glass waste, without paper towels.
Why of the following statements regarding the citric acid titration is NOT CORRECT?
It is not necessary to know the exact amount of soda added to the flask.
What is the most likely cause of water not being displaced in the buret once the tablet has been dissolved?
Leaks in the system; fix them with parafilm.
Which of the following would be considered the analyte in this week's lab?
NaOH
If you spill a chemical on the floor or the bench, you should:
Notify your TA and obtain proper clean-up instructions
Which of the following may be disposed of in the regular trash:
Paper towels
What should you do if you measure 55.3 mL (59.4 g) of milk?
Record the mass and press on because you care more about exact mass than exact volume here.
If large portions of skin have come into contact with the chemicals, use the [x] which is located in the hallway.
Safety shower
You will prepare solutions this week using a volumetric flask. What should you do if you add water too quickly and your solution goes above the graduation line?
Start weighing another sample of copper sulfate because you need to start over.
Which of the following statements regarding heating the acetone mixture in exercise 2 is incorrect?
The beaker should be cool enough that you can remove it from the hot plate with your bare hands.
You should always inspect glassware carefully before using to make sure it does not have any cracks or chips.
True
Which of the following is NOT included in the next ionic equation we are using this week?
The soluble salt
Why is the addition of 5 mL of cold distilled water to the test tube holding your aspirin crystals a necessary step and why should this step be carried out carefully?
The water will destroy unreacted acetic anhydride and it releases heat.
Which of the following statements regarding the Benedict's Test for Reducing Sugars is INCORRECT
This test will give a positive result for any sugar.
Calculate the theoretical yield of aspirin given that 0.909-g of salicylic acid was reacted with excess acetic anhydride.
Yes, it is OK. Your calculations will take care of things.
Which of the following statements regarding the use of the Buchner funnel is INCORRECT?
You are limited to only the amounts of 'wash' solvents that are listed in the manual.
Your manual mentions Dalton's Law of Partial Pressures. If you attribute all of the generated gas to CO2 production, which of the following statements is true?
Your calculated value for the generated CO2 will be higher than it actually is because you are not considering the vapor pressure of water.
Which of the following statements best describes the spot size you should aim for when spotting your TLC plates with the dyes?
as small as possible
What color should be observed when a small drop of basic solution is touched to litmus paper
blue
A positive result for the FeCl3 test should result in which of the following observations?
dark purple solution
What are the most dominate intermolecular forces present in acetone?
dipole-dipole forces
The following reaction can BEST be described by which of the categories listed below?
gas
Which of the following answers lists the components for the microcolumn in the order you should add them.
glass wool, sand, silica gel, solvent and dye, sand
Which of the following statements regarding the collection and use of pH data during this week's lab is FALSE?
pH data should be collected following completion of all of the reactions.
Ammonia (NH3 or NH4OH) molecules are capable of hydrogen bonding. Would this be an example of a polar or a nonpolar solvent.
polar
How many moles of CO2 gas are generated if you collect 44.42-mL of the gas over water at 24.5 degrees C and 1.02-atm?
.0019
What is the citric acid concentration in a soda if it requires 33.52-mL of 0.01-M NaOH to titrate 25-mL of soda?
.0045
A lab group made a copper amine stock solution with a concentration of 0.021 M. A group member transfers 8.83 mL of this solution to a 25 mL volumetric flask and dilutes to the line with water. What is the concentration of the resulting solution? Report your answer to 3 decimal places.
.007
A tablet generated 0.001 moles of CO2. If that tablet had an initial mass of 0.5-g, what percent of the tablet was bicarbonate?
.0080
How many moles of phosphate were isolated from a sample of milk if 1.399-g of calcium phosphate were isolated after the completion of exercise 3? Report your answer to 4 decimal places and WITHOUT units.
.009
What mass of copper sulfate pentahydrate is necessary to produce 25 mL of a solution with a concentration of 0.021 moles per liter? Report your answer to 3 decimal places.
.131
A reaction involving acetic acid has an enthalpy change of 55.7 kJ/mol. What is the concentration of 27.09-mL of this acetic acid solution if the reaction it is involved in evolves 626.89-J of heat?
.42
What is the maximum amount of gas that your apparatus can collect? (In other words, how much water should you aim to displace?)
45-55 mL
Excess of which of the following reagents should be placed in the designated chemical waste containers?
Acetone
Which of the following definitions DOES NOT describe a catalyst?
Adding a catalyst ensures a much larger yield of product.
All of the following are a safety hazard in the lab except:
Carrying a reaction out in the hood that generates flammable or toxic fumes
If a fellow lab member splashes chemicals in their eyes, escort the person to the [x] and rinse their eyes for at least 5 minutes with water.
Eyewash station
If a fire breaks out while you are in the laboratory, you should try to extinguish it yourself, then let your TA know about the fire
False
If you wear prescription glasses, you do not need to wear safety goggles in the lab.
False
It is ok to transfer any unused chemical back into the container it came from
False
Only the TA needs to know the location of the fire extinguishers in the lab.
False
Which of the following statements best describes the line you will create on the bottom of your TLC plate?
It should be made in pencil about a centimeter from the bottom of the plate.
Which of the following is the catalyst in the synthesis of aspirin?
Sulfuric acid
Which statement BEST describes the relationship between the spots that are developed on the TLC plate and the spots that are separated by the microcolumn?
The spots will appear in opposite order (ex: blue,pink and pink, blue) on the TLC plate and the microcolumn because we add solvent from the top in one and the bottom in the other.
A fat molecule will likely be more soluble in heptane (an organic solvent) then in aqueous solution.
True
If you splash a chemical in your face, you should move to the eyewash station and rinse your face for 5-10 minutes.
True
It is a good idea to wash your hands before leaving the laboratory for the day.
True
How will you know that the pressure of your system is equalized and that it is okay to record an initial and/or final volume?
When the meniscus in the funnel is level with the meniscus in the buret.
he function group R-COOH is referred to as an organic ___ and the functional group R-OH is referred to as a generic ___ .
acid, alcohol
For this experiment, you will graphically determine how the concentration of a solution affects absorption. Which response represents the values of the independent (x) and dependent (y) axes that will be on the graph you prepare, respectively.
concentration (M), absorbance
Which solution should be added to the calorimeter first?
excess reagent
A denatured protein will be more soluble in water than a protein in it's native, folded state.
false
Two clear/colorless solutions are mixed quantitatively. No noticeable precipitate or gas is observed, and the reaction is performed on a small scale (in a well plate). The lab group should record "no reaction" in their notebook.
false, note NVC
Which pair of items are useful in extinguishing small fires?
fire extinguisher and blanket