CH 116 Lab Final

phenolphthalein is accurate for the titration of a strong or weak ___ with a strong ___, but would not be acceptable for the titration of a weak ___ with a strong ____

(IN ORDER>) acid, base, base, acid

Solve for the unknown value in the following equation, y=mx+b, given that the slope and intercept of the line are 7.458 and 0.203, respectively, and that the y value of your ordered pair is 7.14.

0.93

A student delivered 15.92 mL (V1) of 3.54 % stock solution (M1) using a graduated pipette into a 50.00 mL (V2) volumetric flask. Distilled water was added to the flask to the graduation mark and mixed well.

1.127

Calculate the theoretical yield of aspirin given that 0.958-g of salicylic acid was reacted with excess acetic anhydride.

1.25

Given that the density of aluminum is known to be 2.69 g/mL, what volume of water (in mL) would a aluminum cylinder with a mass of 32.87 grams displace?

12.22

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

Report the volume of liquid contained in the graduated cylinder to the X number of decimal places

2 (Ex: 9.10 or 5.98)

A group of students performed a series of titrations in the laboratory and found that their unknown sample had an average concentration of 14.8 M. The accepted value for their sample is 15.18 M. What should the group report as their % error?

2.503

Jack and Jill are lab partners. Jill delivered 3.81 mL of a 18.56 % 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?

2.83

What is the molar mass of KHP?

204 g/mol

What is the ratio of citric acid and sodium hydroxide (NaOH) based on the balanced chemical equation?

3 NaOH: 1 Citric acid

the functional group R-OH is referred to as a generic

alcohol

Benedict's Test uses a Cu2+-citrate complex to oxidize the ___ ___ to a carboxylic acid

aldehyde group

Which of the following types of molecules will give a positive result for the Benedict's test? white sugars aldehydic sugars ketone sugars powdered sugars brown sugars

aldehydic sugars

What type of sample(s) should be included on the TLC plate? Your synthesized aspirin All of the above Salicylic acid Commercial aspirin

all of the above

The generic name for one of twenty different biological molecules, each having a carboxylic acid group on one end of the molecule and an amine group on the other end

amino acid

Regarding titration, which solution is being studied?

analyte

Typically, titrations involve two solutions: an ___ solution and a ____ solution

analyte, standard

All of the following are a safety hazard in the lab except: A. Coats on the lab bench B. Carrying a reaction out in the hood that generates flammable or toxic fumes C. Food D. Directly inhaling vapors from an open chemical container E. Disposing of excess acid in the liquid organic waste container

b

Rf factor is calculated by dividing X by X

distance traveled by component x/distance traveled by solvent

the main carbohydrate in milk and is a disaccharide containing the monosaccharides glucose and galactose

lactose

The concentration of acetic acid in the vinegar solution in the HEAT OF REACTION LAB can be determined by

measuring the heat and using the ∆Hº determined in Exercise 1

What is the name given to a bond between two amino acids in a protein?

peptide

Chemical bond formed between 2 molecules when the carboxylic acid group of 1 molecule reacts with the amine group of the other, releasing water

peptide bond

When two amino acids react, a ___ ___ is formed between the carboxylic acid group of one amino acid and the amine group of a second amino acid

peptide bond

The color of solution containing analyte turns (color) ___ when titration is reached

pink

Acetonitrile (CH3CN) molecules interact using dipole-dipole interactions. Would this be an example of a polar or a nonpolar solvent?

polar

Benedict's test gives a ___ result for aldehydic sugars (found in lactose), but not for ketone sugars such as fructose.

positive

a reagent that has known composition and will react the same way every time

primary standard

Large, polymeric structures made up of amino acid

proteins

what color should the solution containing your analyte turn when the endpoint of the titration has been reached? (analysis of aspirin lab)

purple

indicator

reagent that will change color when the reaction is complete or when the chemical property of the solution changes

What are some ways you could purify synthesized aspirin in the laboratory? **

recrystallization

To test for the presence of lactose, you take advantage of its ability to reduce Cu2+ to Cu2O in alkaline solutions, forming a __ colored precipitation product

rust

carbohydrates that have the general formula Cn(H2O)m

saccharides (sugars)

If large portions of skin have come into contact with the chemicals, use the [x] which is located in the hallway.

safety shower

single bonds between many carbon atoms (fats)

saturated fatty acids (*S*ingle bonds > *S*aturated)

to measure in a standard way to determine the concentration accurately

standardize

A reaction involving acetic acid has an enthalpy change of 55.7 kJ/mol. What is the concentration of 26.29-mL of this acetic acid solution if the reaction it is involved in evolves 601.04-J of heat?

0.41

If a reaction evolves 650.38-J of heat as 0.019-moles of water are produced, what is the \Delta H ΔHº of this reaction (in kJ/mol)?

-34.23

How much heat (in J) is evolved when two solutions are mixed together to give 40-g of solution and a temperature change of -5 degrees Celsius?

-836.8

How many moles of aspirin in a tablet with 250mg active?

.0014 moles

How many moles of water are produced when 34.2 mL of 0.100 M NaOH is mixed with 22.4 mL of 0.08 M acetic acid?

.00179

How many moles of water are produced when 24.3 mL of 0.100 M NaOH is mixed with 31.4 mL of 0.08 M acetic acid?

.00243

A lab group made a copper amine stock solution with a concentration of 0.02 M. A group member transfers 6.06 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?

.005

What mass of copper sulfate pentahydrate is necessary to produce 25 mL of a solution with a concentration of 0.021 moles per liter?

.131

The enthalpy of reaction for the combustion of ethane is -1426 kJ/mole ethane. How many moles of ethane are present when 357 kJ of energy is released upon combustion?

.25 moles

Calculate the Rf value for the measured spot on this TLC plate. Report your result to 2 decimal places. [8.35 and 3.72]

.45

How many moles of Aspirin are present in a tablet that has 250-mg of active ingredient?

0.0014

What is the citric acid concentration in a soda if it requires 34.43-mL of 0.01-M NaOH to titrate 25-mL of soda?

0.0046

How many moles of phosphate were isolated from a sample of milk if 1.202-g of calcium phosphate were isolated after the completion of exercise 3 in the MILK lab?

0.0077

If an experiment was run in a 0.50 L flask at a pressure of 1.082 atm in a room that was 295.53 K, how many moles were involved in the experiment?

0.0223

If you have 93 grams of a substance with a formula mass of 239.465 g/mol, how many moles do you have?

0.388

A group of students perform a series of dilutions and produce a calibration curve with the general equation y=ax+b. If one of the points they plotted was (0.98, 0.41) and the intercept was 0.01, what was the slope (a) of their line?

0.408

Standard deviation is used to assess the precision of a set of data. You will use the standard deviation throughout the General Chemistry laboratory to assess small sets of data (usually three trials). For small sets of data scientist use σn-1 . The calculation of σn-1 is outlined in the manual as part of the introduction. Additionally, most scientific calculators will perform this calculation easily, and Microsoft Excel will do this by using the standard deviation function: =STDEV(reference cells). Calculate the standard deviation of the set of numbers: 4.384 4.529 10.517 Report your answer to the thousandths place (0.001) so that Canvas will figure out what you have done.

3.4997

What is the MINIMUM temperature change that is acceptable to record in your manual? 4 degrees C 2 degrees C 8 degrees C 12 degrees C

4

a student delivered 5.03 mL of 20.0% sugar stock solution using a graduated pipet into a 25.00- mL volumetric flask. Distilled water was added to the flask to the graduation mark and mixed well. Whats the final concentration?

4.02%

A laboratory group began the recrystallization process with. 0.923-grams of synthesized aspirin. After they carefully completed the necessary steps to purify their sample via recystallization, they were left with 0.505-grams of aspirin. What is the group's percent yield?

54.7

Calculate the average for the set of values. 50.49 71.75 60.95

61.063

Given that the density of iron is 7.87 g/mL, what is the mass in grams of an iron cylinder that displaces 9.78 mL of water?

76.97

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 7.71 mL and that the density of lead is known to be 11.34 g/mL, what is the mass of his cylinder?

87.43

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.

9.0

Calculate the theoretical yield of aspirin given that 3.52-mL of acetic anhydride was reacted with 0.9457-g of salicylic acid.

?? .00138

Which of the following answers lists the components for the microcolumn in the order you should add them. A) glass wool, sand, silica gel, solvent and dye, sand B) glass wool, solvent and dye, sand, silica gel, sand C) glass wool, sand, silica gel, sand, solvent and dye D) glass wool, silica gel, sand, solvent and dye, sand

A

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? A. 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. B. The spots will appear in the same order (ex: blue,pink and blue, pink) on both the TLC plate and the microcolumn because we are using the same solvent. C. The spots will appear in the same order (ex: blue,pink and blue, pink) on both the TLC plate and the microcolumn because we add solvent from the top in one and the bottom in the other. D. The spots will appear in opposite order (ex: blue,pink and pink, blue) on the TLC plate and the microcolumn because we are using two different solvents.

A

Solvent A gives Rf values for the two unknown dyes of 0.28 and 0.67. Solvent B gives Rf values for the same two unknown dyes of 0.31 and 0.83. Based on this, would you choose Solvent A or Solvent B to separate the dye using your silica gel column?

A, larger separation of dyes

Which of the following statements best describes the proper disposal of the micro column? A. In the trash, without paper towels. B. In the glass waste, without paper towels. C. In the glass waste, wrapped in paper towels. D. In the trash, wrapped in paper towels.

B

Which of the following statements regarding the use of the Buchner funnel is INCORRECT? A. You should wet the filter paper with the same solvent that is in your filtrate prior to turning on the vacuum. B. You are limited to only the amounts of 'wash' solvents that are listed in the manual. C. You must clamp the funnel to the ring stand prior to using it. D. When filtering a solid, you should add the 'wash' solvent to the glassware that originally held the solid and filtrate before adding it to the funnel. E. When 'washing' your filtered product, you should turn the vacuum off before adding the 'wash' solvent to remove as many impurities as possible.

B

You will prepare solutions in the copper amine lab using a volumetric flask. What should you do if you add water too quickly and your solution goes above the graduation line? A.) Remove the excess water using a transfer pipet. B.) Start weighing another sample of copper sulfate because you need to start over.

B

Explain why writing "no visible change" is a better observation than "no reaction"

Because sometimes the reactants and products are all colorless so a reaction may have happened but not been observed

Explain why measuring the pH before/after mixing might/ might not be useful. Which time will be more useful?

Before, since pH can be affected by chemicals in the water. pH is an important indicator of water that is changing chemically

___ ____ uses a Cu2+-citrate complex to oxidize the aldehyde group to a carboxylic acid

Benedict's Test

Which of the following would be considered the analyte in the SODA lab?

Both NaOH and Citric acid (2 different titrations)

The bicarbonate ion decomposes to ___ in the presence of a small amount of acid.

CO2

You will isolate the phosphate ion, PO4 3- by adding ___, which precipitates the phosphate as solid calcium phosphate.

Ca2+

A laboratory technique used to determine the amount of heat transferred during a chemical or physical change

Calorimetry

What are the 4 components of milk?

Carbohydrates (sugars), lipids (fats), proteins, and phosphate

What should you do if you measure 55.3 mL (59.4 g) of milk? A) Pour the milk down the sink and start again. B) I dunno, ask the TA what the milk would weigh on the moon. C) Get a disposable pipet and painstakingly get exactly 50.00 mL. D) Record the mass and press on because you care more about exact mass than exact volume here.

D

Why of the following statements regarding the citric acid titration is NOT CORRECT? A. It is necessary to boil the soda prior to beginning your titration. B. The soda solution should be cooled to room temperature before beginning your titration. C. The carbonation in the soda can react with NaOH and cause your calculations to be wrong. D. It is not necessary to know the exact amount of soda added to the flask.

D

a 10-mL graduated pipet

Mohr pipet

Distinguish between a polar solvent and a nonpolar solvent.

Polar solvents have a dipole moment (while nonpolar do not) due to intramolecular bonds between atoms with different electronegativity.

How do you prepare a dilution?

Prepare three solutions. To prepare the first solution, quantitatively transfer a small portion of the stock solution to the 25 mL volumetric flask and slowly add water to the mark. Transfer the solution to a separate clean, dry storage container (a beaker or test tube) so that the volumetric flask can be used to prepare another solution. Repeat until 3 solutions are prepared

Explain why the carbonation must be removed from the soda prior to the titration (SODA LAB)

The bubbles that result from carbonation will cause errors in your analysis

____ represents a functional group that is unique to each amino acid.

R

the __ _____ determine the identity and properties of a particular fat

R groups

calibration curve: relationship between absorbance and concentration

The Lambert-Beer law states that the absorbance of a light absorbing material is proportional to its concentration in solution

Provide a simple explanation of how the spectrophotometer works

To determine the best peak at which to measure the absorbance of all of your solutions by scanning across all wavelengths (spectrophotometer) in the visible range and determining the most useful wavelength for measuring the absorbance of the copper amine solution

Hydrophobic

Water fearing

How is a precipitate formed?

When cations and anions in an aqueous solution combine to form an insoluble ionic solid

A positive result for the FeCl3 test should result in which of the following observations? a) A deep purple solution b) A clear/colorless solution c) A pale yellow solution d) A bright red solution

a

Based on your existing knowledge of TLC, which of the following statements regarding the thin layer chromatography portion of this experiment is NOT CORRECT? a. The solvent that aspirin is less soluble in should be used as the mobile phase. b. The Rf values of the spots are all fairly close together. c. The sample spots are only visible under a UV lamp. d. You will need to draw around the spots on the plate while it's under the UV lamp.

a

In what order should the following steps be performed for a successful recrystallization? I. Place the beaker with the aspirin in an ice bath. II. Add the chilled second solvent slowly until you see a few crystals. III. Dissolve the synthesized aspirin in the solvent it's most soluble in. IV. Weigh the purified aspirin and calculate the percent yield. a. III, II, I, IV b. II, IV, III, I c. I, II, III, IV d. IV, III, II, I

a

Which of the following should you look out for PRIOR to starting your titration? Correct! a. All of the above b. Loose O-rings c. That the stopcock is horizontal before adding titrant d. Air bubbles in the tip of the buret

a

Why is the addition of the bicarbonate solution necessary when making the flavoring esters? a. It is added to react with excess acetic acid so the acid doesn't mask the smell of the ester. b. It is added to react with excess sulfuric acid so the acid doesn't mask the smell of the ester. c. It is added to react with excess acidic anhydride so the acid doesn't mask the smell of the ester. d. It is added to react with excess carbonic acid so the acid doesn't mask the smell of the ester.

a

What is the general form of a single displacement reaction? Provide an example of a single displacement reaction

a reaction in which one element is substituted for another element in a compound; A +BC > AB+ C

What is the general form of a double displacement reaction? Provide an example of a double displacement reaction

a reaction in which parts of two ionic compounds are exchanged, making two new compounds; AB + CD > AD + BC

The function group R-COOH is referred to as an organic

acid

Why is the addition of cold distilled water to the container holding the aspirin you are trying to isolate a necessary step and why should this step be carried out carefully? a. The aspirin is less soluble in water than ethanol- the water keeps the crystals from separating from solution. b. The aspirin is more soluble in ethanol than water - the water helps the crystals separate from solution. c. The aspirin is more soluble in water than ethanol- the water keeps the crystals from separating from solution. d. The aspirin is less soluble in ethanol than water - the water helps the crystals separate from solution.

b

What color should be observed when a small drop of basic solution is touched to litmus paper in the MILK lab?

blue (bases turn litmus paper blue)

piece of glassware that is designed to accurately deliver between 30 and 45 mL of titrant

buret

How can the amount of heat released by a simple acid-base reaction be calculated?

by observing the heat absorbed by the solution surrounding the reaction

Which pair of items are useful in extinguishing small fires? a. safety shower and eyewash station b. Fire extinguisher and safety shower c. fire extinguisher and blanket d. fire blanket and eyewash station

c

a device that absorbs heat in a known manner

calorimeter

the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity

capillary action

Each amino acid has a ___ ___ group on one end of the molecule and an ____ group on the other end

carboxylic acid, amine

a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

catalyst

primary acid in citrus-flavored sodas

citrus acid

For the copper amine lab, 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

Determine the _________________ in the soda by placing a small portion of the soda (15-25mL) in an Erlenmeyer flask, adding phenolphthalein, and delivering sodium hydroxide to the end-point

concentration of citric acid

8 M H2SO4 and glacial acetic acid are both ____ acids

corrosive

Adding the bicarbonate solution to the organic acid should result in which of the following noticeable changes? a. Formation of a precipitate b. An obvious color change c. An increase in reaction temperature d. Evolution of gas

d

The following are unacceptable clothing for the lab except: a. Short skirts b. Tank tops c. High-heeled shoes d. Long-sleeved shirts

d

Which of the following definitions DOES NOT describe a catalyst? a. A small amount of catalyst will make a significant change in rate. b. A catalyst is not consumed in the reaction. c. A catalyst speeds up the rate of a chemical reaction. d. Adding a catalyst ensures a much larger yield of product.

d

What are the intermolecular forces present in acetone?

dipole-dipole and London forces

Which of the following statements regarding the Benedict's Test for Reducing Sugars is INCORRECT? a) The contents of the test tubes can be disposed of down the sink. b) You should set up your water bath for this portion of the experiment at the beginning of the lab period. c) This test tells you only whether or not sugar is present in the sample; you cannot determine a quantity. d) The provided 1% glucose solution is used as a positive control. e) This test will give a positive result for any sugar.

e

Which solution should be added to the calorimeter first? The excess reagent The limiting reagent ALWAYS the solution in the red cylinder ALWAYS the solution in the yellow cylinder

excess

It is ok to transfer any unused chemical back into the container it came from

false

The following solutions can be disposed of down the sink: acetone, calcium nitrate, milk, and water. (true or false)

false

If you splash a chemical in your face, you should move to the eyewash station and rinse your face for 1-5 minutes.

false (5-10 minutes)

type of lipid composed of a trihydroxy alcohol (glycerol) and long chain fatty acids (RCOOH)

fats

What are the most dominate intermolecular forces present in water?

hydrogen bonds

When placed in an aqueous solution a protein will fold up on itself to form what is called a "___" structure

tertiary

Acetic anhydride is often used instead of acetic acid in the commercial preparation of aspirin because

the reaction reaches completion and acetic anhydride reacts more quickly

All organic compounds used in this week's lab (analysis of aspirin) are flammable and therefore a hot plate should be used to warm the water bath. (true or false)

true

If the thermometer is broken you should not dispose of in regular trash.

true

NaOH is a corrosive reagent that can cause burning/blistering if it comes into contact with skin. (true or false)

true

NaOH is corrosive and can result in burning/blistering the affected area of skin if it comes into contact with it.

true

You should always inspect glassware carefully before using to make sure it does not have any cracks or chips.

true

double bonds between many carbon atoms (fats)

unsaturated fatty acids

hydrophilic

water loving

Citric acid is a (strong/weak) acid and will react with strong base to form salts

weak

Potassium hydrogen phthalate is a (strong/weak) monoprotic acid

weak