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