Chem 2 Lab Final Exam
The titration of vitamin C with iodine proceeds according to the given equation. C6H8O6+I2⟶C6H6O6+2HICX6HX8OX6+IX2⟶CX6HX6OX6+2HI Suppose it takes 18.95 mL of 0.0026 M I2 solution to reach the end point of the titration. How many moles of vitamin C are present?
0.000049 moles vitamin C
The titration of vitamin C with iodine proceeds according to the given equation. C6H8O6+I2⟶C6H6O6+2HICX6HX8OX6+IX2⟶CX6HX6OX6+2HI Suppose it takes 23.31 mL of 0.0053 M I2 solution to reach the end point of the titration. How many moles of I2 reacted? Vitamin C Quiz
0.00012 moles iodine
Calculate the Rf value for a spot in a TLC experiment if the solvent moved 11.4 cm and the spot moved 8.8 cm from the origin. Spinach Lab
0.77
What is the correct name for the pictured organic structure?
1,2-dibromo-4-methylcyclohexane
Identify the name for the molecule pictured. - see photos
1-butanoic acid
Suppose you are titrating an acid of unknown concentration with a standardized base. At the beginning of the titration, you read the base titrant volume as 2.96 mL. After running the titration and reaching the endpoint, you read the base titrant volume as 17.12 mL. What volume, in mL, of base was required for the titration?
14.16 mL
Aspirin can be prepared from salicylic acid ( C7H6O3CX7HX6OX3 ), which has a molar mass of 138.12 g/mol, and acetic anhydride ( C4H6O3CX4HX6OX3 ), which has a molar mass of 102.04 g/mol. The density of acetic anhydride is 1.082 g/mL. C7H6O3+C4H6O3⟶C9H8O4+C2H3O2CX7HX6OX3+CX4HX6OX3⟶CX9HX8OX4+CX2HX3OX2 What is the yield, in grams, of aspirin ( C9H8O4CX9HX8OX4 ), which has a molar mass of 180.15 g/mol, possible when reacting 2.10 g of salicylic acid with 1.15 mL of acetic anhydride? Type answer:
2.2
Calculate the percent by mass of a solution made from 17 g NaCl (the solute) and 68 g water. Casen Quiz - Q3
20
What is the correct reading of the volume in the pictured buret? Make sure to report your reading with the appropriate significant figures.
25.60 mL
Aspirin can be prepared from salicylic acid ( C7H6O3CX7HX6OX3 ), which has a molar mass of 138.12 g/mol, and acetic anhydride ( C4H6O3CX4HX6OX3 ), which has a molar mass of 102.04 g/mol. The density of acetic anhydride is 1.082 g/mL. C7H6O3+C4H6O3⟶C9H8O4+C2H3O2CX7HX6OX3+CX4HX6OX3⟶CX9HX8OX4+CX2HX3OX2 What is the theoretical yield, in grams, of aspirin ( C9H8O4CX9HX8OX4 ), which has a molar mass of 180.15 g/mol, possible when reacting 3.23 g of salicylic acid with 3.60 mL of acetic anhydride? Synthesis of Aspirin Quiz
4.21
Fill in the palindromic sequence of the given DNA strand containing six bases.
5'GACGTC3' 3'CTGCAG5'
Identify the term that applies to each definition.
A unit commonly used in spectrophotometry that is inversely proportional to energy and commonly measured in nanometers - Wavelength A measurement of the amount of light that passes through a sample - Transmittance A sample prepared using the solvent and any other chemicals in the sample solutions, but not the absorbing substance -Blank A square-shaped container, typically made of quartz, designed to hold samples in a spectrophotometer-Cuvette A measurement of the amount of light taken in by a sample- Absorbance
The TLC plate remains in the chamber even after the solvent has reached the top of the plate.
Accurate Rf values cannot be determined.
The solvent line is not marked after the TLC plate is removed from the chamber.
Accurate Rf values cannot be determined.
Which tests show can be used to show that a phenol is present? Select one or more:
Acidity test Iron(III) chloride test
How can you remove the protein casein from a sample of non-fat milk?
Add acid to change the protein's tertiary structure, which triggers solid formation.
A polymer formed as monomers link together without forming a byproduct.
Addition Polymer
What is a protease? An enzyme that breaks down a protein into individual amino acids A protein consisting of a chain of amino acids A component of foods such as fruit juices All of the above are correct.
All of the above
Which statement concerning the effectiveness of enzymes is NOT true?
Although the actions of different enzymes may vary, the effectiveness of each particular enzyme is constant.
What functional groups are present in all amino acids?
Amine Carboxylic acid
What are the building blocks of proteins?
Amino acids
Suppose you are going to perform a TLC experiment, which materials will you use to prepare the TLC development chamber?
Beaker Filter paper Watch glass
What are lipids?
Biological molecules characterized by solubility in organic solvents
The molecular formula for the simple alkane butane is:
C4H10
Now, consider the structure of cyclobutane. The molecular formula of cyclobutane is:
C4H8
Which four molecules are tested for in the lab?
Carbohydrates Starch Proteins Lipids
What elements make up a carbohydrate?
Carbon Hydrogen Oxygen
Aspirin was formed to reduce the irritation of salicylic acid. However, aspirin can still disturb the stomach. Which functional group in aspirin is responsible for stomach irritation?
Carboxylic acid
In a TLC experiment, how do you identify the components of an unknown mixture?
Compare the Rf values of the mixture components to the Rf values of pure known compounds.
After an electrophoresis experiment, how are the lengths of the DNA fragments in each lane determined?
Comparing to a standard DNA ladder in one lane
A polymer formed as monomers link together, forming a small molecule as a byproduct.
Condensation Polymer
Which metal is responsible for the color change in a Benedict's test?
Copper
Fill in the words to complete the steps in the process of recrystallization.
Dissolve a substance in a minimal amount of hot solvent. Allow the solvent to cool, precipitating the substance while impurities remain in solution. Filter the mixture to collect the pure substance.
Determine whether each phrase describes carboxylic acids or esters.
Do not form hydrogen bonds amongst themselves and have higher vapor pressure - Esters Notable for their pleasant fragrances -Esters Form hydrogen bonds amongst themselves and have lower vapor pressure - Carboxylic acids Their reactions with base are known as saponifications- Esters Usually have a sour odor - Carboxylic acids Their reactions with base are known as neutralizations - Carboxylic acids
Identify the name for the molecule pictured. - see photo
Ethyl propanoate
Identify the expected result of the iodine test with different carbohydrates.
Glucose - No reaction Sucrose -No reaction Starch -Color change Amylopectin - No reaction
Carboxylic acids, such as benzoic acid, behave as other acids and can also be neutralized by the addition of base. What are the products of the neutralization of benzoic acid with sodium hydroxide?
H20 and see photos
A flexible polymer used in the manufacturing of grocery bags. The molecular structure is (C2H4)n(CX2HX4)n .
High-density polyethylene
When testing the solubility of compounds containing -OH groups, check the solubility in water first.
If the compound is soluble under that condition, its solubility in aqueous NaOH does not need to be tested.
In order for a substance to be an effective mobile phase in a chromatography experiment, it must be able to move
In order for a substance to be an effective mobile phase in a chromatography experiment, it must be able to move different components of a mixture at different rates.
The titration of vitamin C with iodine proceeds according to the given equation. C6H8O6+I2⟶C6H6O6+2HI
In this reaction, vitamin C is oxidized and iodine is reduced.
A reagent added to the analyte solution that changes color when the reaction is complete When the required amount of one solution has been added to the second solution to complete the reaction Glassware that allows a solution to be precisely and slowly added to another solution
Indicator Endpoint Buret
Iron(III) chloride can be used to assess the purity of aspirin synthesized from salicylic acid
Iron(III) chloride does not react with aspirin because the reaction requires a phenolic functional group which is present in salicylic acid but not aspirin.
Which substance is not a carbohydrate?
Lipid
Do not use open flames, like Bunsen burners.
Many organic chemicals are flammable.
Use glass containers, unless instructed to do otherwise.
Many organic chemicals dissolve plastics.
Rinse the glassware with organic solvents after the experiment.
Many organic chemicals do not dissolve in water.
Perform procedures in the fume hood, if possible.
Many organic chemicals involve harmful vapors.
Identify the medical applications of aspirin.
Pain killer Fever reducer Anti-inflammatory agent Anti-coagulant
How can you improve your ability to see the indicator color change at the endpoint of a titration?
Place a piece of white paper under the analyte flask throughout the titration.
A polymer produced through a condensation reaction, with applications ranging from clothing to packaging.
Polyethylene terephthalate
A polymer is a macromolecule made of many repeated subunits, known as monomers.
Polymers can be natural, such as proteins, or synthetic, such as plastics.
Polypropylene is a polymer with a density of 0.89 g/mL. Review the density table given and identify the expected observations if polypropylene is added to a beaker containing each liquid. Liquid Density (g/mL) water1.00 methanol 0.79 ethanol 0.79 hexane 0.66
Polypropylene will sink in ethanol. Polypropylene will float in water.
A rigid, brittle polymer used in disposable food containers. The backbone of the polymer contains phenyl rings.
Polystyrene
A rigid polymer used often in construction materials. The structure contains a halogen.
Polyvinyl chloride
What effect do restriction enzymes have on DNA?
Restriction enzymes cleave DNA at specific sequences into fragments.
A value that quantifies the distance traveled by a substance relative to the distance traveled by the solvent
Rf
Esters are formed from the reaction of an alcohol and a carboxylic acid. Identify the alcohol and carboxylic acid combination necessary to make each pictured ester.
See photos
What is the correct structure of aspirin?
See photos
What property is used to separate DNA fragments during a gel electrophoresis experiment?
Size
Which statements accurately describe soap?
Soaps should be weakly alkaline in solution. Soaps react with ions in hard water to create a precipitate. Soaps are both hydrophobic and hydrophilic.
Which states of matter can be separated by gravity filtration?
Solid and liquid
What visible signs indicate a precipitation reaction when two solutions are mixed?
Solid settling out in the test tube A hazy or cloudy appearance
Which process would restore a fatty acid from a soap?
The addition of an acid
What changed between the butane and cyclobutane structures?
The loss of 2 hydrogen atoms
Identify the number of amino acids that matches each description.
The number of amino acids that exist in the human genetic code Natural amino acids - 20 The number of amino acids that humans require through diet Essential amino acids - 9 The number of amino acids that can be made by the human body Nonessential amino acids - 11
The mobile phase used does not move any of the spots at all.
There can be no separation of components.
Pen rather than pencil is used to draw the lines on the plate.
There will be smears on the TLC plate.
Solution of known concentration that is slowly added to a solution of unknown concentration
Titrant
Process of slowly adding a solution to react with another solution and determine the concentration of one of the solutions based on the reaction between them
Titration
Several foods were tested using the Biuret reagent. The results are provided in the table. Food Observation after Biuret Reagent Yogurt Purple Water Blue Cottage cheese Purple/lavender Chicken broth Purple Honey Blue
Yogurt - Protein present Cottage cheese- Protein present Water - No protein present Chicken broth - Protein present Honey - No protein present
Suppose you are setting up a chromatography experiment to separate a mixture.
Your chosen mobile phase must dissolve the mixture and your chosen stationary phase must allow the mixture to pass through.
A method used to separate components of a mixture
chromatography
The substance that carries the components of a mixture
mobile phase
What color is Sudan III?
red
Determine the type of alcohol represented by each structure.
see photos
Eugenol is a molecule that contains the phenolic functional group. Which option properly identifies the phenol in eugenol?
see photos
Identify the name of each given common carboxylic acid.
see photos
Label the alcohols as primary, secondary, or tertiary.
see photos
The cleaning ability of soap is based on its structure. Which structures represent compounds that can be used as soaps?
see photos
dentify the name for the molecule shown.
see photos - Pentan-2-ol
The substance to which the sample is bound at the start of an experiment
stationary phase
For your data graph in the Proteases experiment, identify which variables will be plotted on each axis.
y-axis - absorbance x-axis -time (sec)
Which is NOT a good source of information about the hazards that affect waste disposal in a chemistry lab?
your lab partner
