CHEM 1174 Lab Final
If you were to dilute a 100 mg/mL solution to a 25 mg/mL solution, what is the dilution factor?
1:4
What is the molarity of a solution if 1.0 moles of solute is dissolved in 500 mL of water?
2.0 M
How long should the methods section of your post-lab report be?
3-5 sentences
If you started with 5.05 grams of Copper wire and at the conclusion of the lab had 4.76 grams what is your percent recovery?
94.2%
If you'd like to get Microsoft Excel to do a calculation for you, what do you need to type into the cell first?
=
Filtration
A process that separates materials based on the size of their particles.
Which of these not an example of observations that should be recorded in your notebook while observing these reactions.
Any observation is a worthy observation
Which of the following is another name for vitamin C?
Ascorbic Acid
Personal Protective Equipment
Goggles
Which of the following is iodate?
IO3-
Where should your analyte be placed during a titration?
In the flask or beaker you are titrating into
You have recorded a table of data in your lab notebook that you used to construct a calibration curve. Should you include both a data table and a figure of your calibration curve in your lab report?
No
Decantation
Separates liquid from solid precipitate by pouring off liquid without disturbing solid
Which dilution approach involves using each solution you make as a stock solution that is diluted to produce the next solution?
Serial
Why do you record the mass of the watch glass?
So you can subtract it from the total mass of the watch glass, filter paper, and precipitate.
Consider the reaction occurring in today's experiment. What is the limiting reagent if one mole of CaCl2 is mixed with half a mole of Na2CO3?
Sodium Carbonate
What instrument will you use to measure the emission spectrum for the different sources of light?
Spectroscope
What indicator will you be using in this experiment?
Starch
Safety Equipment
- Eyewash station - Fire extinguisher - Fire blanket - Hoods
Assuming the Bohr Model is applicable, use Equation 3 to calculate the energy associated with an electron in a Mercury atom with a quantum number of 2.
-3.488 x 10^-15 J
Calculate the standard deviation
1. Find the mean 2. Find distances between observations and the mean 3. Square each deviation 4. Add up the squares of each deviation and divide by the number of deviations minus 1 5. Find square root of result
How much 6 M NaOH would you need to make 300 mL of a 2 M NaOH solution?
100 mL
Imagine you completed this lab as described. If the final mass of your mixture was found to be 4.35g but you expected a mass of 3.84g, what is your percent error?
11.7%
In Beer's Law, what does A stand for?
Absorbance
If a measurement closely matches a known value, then the measurement is ________.
Accurate
Calculate the mean
Add all numbers in a list, and divide by how many there are. Also known as the average
Why should there be a data point on a calibration curve at the point (0, 0)?
Because you calibrate the machine with a blank
How do you read a volume of an aqueous solution in a buret?
Bottom of the meniscus at eye level
Which chemical in the mixtures is limestone?
Calcium Carbonate
What color change will be produced at the conclusion of the titration?
Clear to a dark blue or black
During the Reaction 1, what extra precaution should you take?
Close fume hood completely during the reaction
Lab Attire
Clothes that cover and protect you; closed toe shoes
Your protocol asks you to take ONLY the amount of cobalt ion stock solution that you need and no more. Why?
Cobalt solutions are expensive
In Reaction 5, what is the oxidizing agent?
Cu 2+
A beaker is designed to deliver accurate volumes of liquid. T/F
False
It is safe to raise your fume hood sash beyond the safety bumpers to refill your buret. T/F
False
The methods section of your lab notebook should be copied word for word from the protocol. T/F
False
There is no need to clean or rinse your burets before use because those in the lab before you already cleaned them. T/F
False
Vitamin C tablets you by at the store are 100% vitamin C. T/F
False
When writing a methods section, you must be sure to tell your audience (i.e. those reading your report) which buttons to push on the instruments used in your experiments. T/F
False
You are not required to cite your sources for your introduction sections in this course. T/F
False
What should you do if you get HCl on your skin (say, on your arm)?
Flush it with water
What does it mean for an electron to be excited?
It is at a higher energy level
There is something wrong with the calculated change in energy in the top-left cell of Table 2. What's wrong?
It should not be positive
The units of energy for Equations 2, 3, and 4 are not given. What should they be?
Joules
Vitamin C is the reducing agent. What ion does it reduce?
KIO3
Which of these chemicals has historically been used to make soap?
Lye
What does the symbol ?̅ represent?
Mean
In Reaction 4, which atom changes oxidation state?
None - it is not a redox reaction
Patty and Tran are lab partners, and together they construct two calibration curves. Patty's curve has an R2 of 0.998, while Tran's has an R2 of 0.757. Whose calibration curve is better?
Patty's
Filtration separates chemicals based on differences in their ________ properties.
Physical
What is h in the Equation 1?
Planck's constant
What type of reaction is Reaction 2?
Precipitation
What type of reaction is occurring in today's experiment (lab 5)?
Precipitation
Evaporation
The change of a substance from a liquid to a gas
During Reaction 5, a gas is emitted. Why does this make your experiment more dangerous?
The gas is hydrogen which is explosive
Purpose of Lab 1: float an egg
The purpose of this experiment is to use different volumetric glassware and using those measurements to determine the volume of other samples.
Purpose of Lab 2: Separating mixtures using physical and chemical properties (week 2)
The purpose of this lab is to calculate the percentages of known substances with unknown masses
Purpose of Lab 7: Conservation of mass through a cycle of copper reactions
The purpose of this lab is to demonstrate the Law of Conservation of Mass by five chemical reactions.
Purpose of Lab 4: Determining an unknown substance using Beer's Law (week 2)
The purpose of this lab is to determine an unknown concentration of copper sulfate in a sample of pool water
Purpose of Lab 6: Analysis of Vitamin C with stoichiometric titrations (week 2)
The purpose of this lab is to determine the amount of vitamin C in a commercially available product by a redox reaction.
Purpose of Lab 4: Determining an unknown concentration using Beer's Law (week 1)
The purpose of this lab is to dilute five standard solutions to create a calibration curve using absorbance measurements
Purpose of Lab 5: Reaction Stoichiometry, Limiting Reagent, and Percent Yield
The purpose of this lab is to find the molar relationship between reactants and products and use stoichiometry to observe a precipitation reaction
Purpose of Lab 6: Analysis of Vitamin C with stoichiometric titrations (week 1)
The purpose of this lab is to standardize the KIO3 solution for use in the upcoming lab.
Purpose of Lab 3: Light Sources: emission spectrum of H2, Hg, and the sun
The purpose of this lab is to understand an atom's structure better due to light emission.
Purpose of Lab 2: Separating mixtures using physical and chemical properties (week 1)
The purpose of this lab is to use different methods to separate mixtures and to find the percentage of each component.
Why are free radicals bad for our health?
They are highly chemically reactive
During Reaction 6, you will use methanol and acetone. What should be aware of while working with these solvents?
They are highly flammable
When should you update you lab notebook's table of contents?
Throughout the semester
How do you dispose of the used filter papers at the end of this lab?
Throw them in the trash
Computers excel (pun intended) at completing repetitive calculations. T/F
True
Microsoft Excel (or your favorite spreadsheet program) is a useful tool that you should learn. T/F
True
When used properly, TD glassware will still have a small amount of liquid coating the sides. T/F
True
You are graded on how accurately you can determine the composition of your unknown sample. T/F
True
How many times do you need to check the mass of the drying CaCO3?
Until the mass no longer changes
Which type of glassware is not used in this lab?
Volumetric Flask
What setting on the colorimeter do you adjust to get a calibration curve with the greatest slope?
Wavelength
If absorbance is directly proportional to concentration, which of the following is true?
When concentration increases, absorbance increases
How will you deliver accurate volumes in this lab 5?
a buret
What does CaCO3 look like? (Hint: We've worked with this compound in previous labs.)
a white solid
What is a precipitate?
an insoluble solid formed by a reaction in solution
Performing a titration could be used to determine ________.
an unknown amount of analyte
To deliver glassware
buret and graduated pipet
The solid produced in Reaction 3 is ________.
copper (II) oxide
In a colorimeter, what is the container that holds your sample called?
cuvette
Theoretically, the mass of copper before the cycle of reactions should be ________ the mass of copper after the cycle of reactions.
equal to
To contain glassware
graduated cylinder and graduated beaker
Extraction
process of withdrawing, pulling out
Balmer identified a way to mathematically describe hydrogen's spectral lines, but this was in conflict to Rutherford's model of the atom. What feature of Balmer's model did Rutherford ignore?
quantum numbers
Decanting can separate ________ from ________.
solids, liquids
