Chem 123 Lab Exam 1
determine where to dispose of each type of waste -broken flask -titrant solution -unused solid reagent -syring tips
-box lined with puncture resistant bag -nalgene bottle with cap -solid waste container -sharps container
How many kilometers is 2175.4 cm?
.021754
Suppose a sample of vinegar contains 0.0685 g/mL of acetic acid, which has a molar mass of 60.052 g/mol. How many moles of acetic acid are present in a 19.2 mL solution of the vinegar?
.0219
how many liters is 49.9 mL
.0499
suppose you have 350.0 mL of a 0.450 M sodium hydroxide solution. How many moles of sodium hydroxide are in the solution?
.158
Calculate the density (in g/mL) of a solid with the given parameters, rounding your answer to the proper number of significant figures. 9.86 g / 10.43 mL=
.945
Identify the value of each number presented in scientific notation 7.32×10^−4
0.000732
Identify the value of each number presented in scientific notation. 4.65×10^−3
0.00465
Complete the computation: 1.213 + 0.00112 =
1.214
In the experiment, Density of Salt Solutions, a ___ stock solution will be diluted to a concentration of ___ using a ___
10% 5% volumetric flask
Calculate the volume (in cm3) of a rectangular solid with the given dimensions, rounding your answer to the proper number of significant figures. 5.49 cm x 6.324 cm x 3.7 cm=
130
In case of accidental contact with chemicals, how long should the eyes be flushed at the eyewash station?
15 minutes
Perform the calculation, rounding your answer to the proper number of significant figures. 0.120 g + 18.0742 g=
18.194
How many significant figures are in the number 2.1
2
hen recording the volume of a solution delivered from a 10 mL pipet, the recorded volume should include _____ decimal places.
2
Choose the best graduated cylinder to make each measurement in a single use. 5.75 mL of a sucrose solution
A 10 mL graduated cylinder with markings every 0.1 mL
Choose the best graduated cylinder to make each measurement in a single use. 18.5 mL of a NaCl solution
A 25 mL graduated cylinder with markings every 1 mL
outlier
A data point that is very different from the rest of the set
calibration curve
A graph showing the value of some property versus concentration of analyte. When the corresponding property of an unknown is measured, its concentration can be determined from the graph.
What information is needed in order to be prepared for an emergency? Select one or more: A.) Location of lab phone and first aid kit B.) Contact information for emergency personnel C.)Full inventory of all chemicals present in the lab D.) Location of all exits E.) Understanding of where to go should an emergency occur
ABDE
When is the best time to clean glassware during the lab session?
As soon as practical after use
primary container
B
what information does not need to be included on a chemical waste label? A.) Relative amounts of chemical compounds in the container B.) A description of the experiment the chemicals were used for C.) The date the waste container was filled completely D.) Names of the chemical compounds present in the container
B
What are the best practices for safely handling waste in the lab? A.) Remove gloves for better manipulation of the waste containers. B.) Always wear appropriate Personal Protective Equipment. C.) Place any paper towels from the clean-up in the trash. D.) Check labels or instructions before any disposal.
BD
Identify the step that is not recommended when responding to an emergency. Select one: A.) turn off equipment such as bunses burners and gas jets B.) proceed camly and listen for instructions C.) gather your belongings D.) alert your instructor
C
waste label
C
secondary container
D
Where should glassware be stored after it is cleaned
In a drying oven, or designated locations such as drawers or buret racks
titration
Process of determining how much base is needed to fully neutralize an acid analyte
erlenmeyer flask
Used during a titration to prevent loss of solution due to splashing
determine the safest option in the lab if you need your vision to be corrected
Wear corrective glasses or lenses under your safety goggles for the whole experiment, but always check with your TA or Instructor for your school's policy
When describing the uncertainty of a measurement, the term ___ refers to the closeness between a measurement and its accepted value, whereas the term ___ refers to the closeness among a set of measurements.
accuracy precision
When describing the uncertainty of a measurement, the term ___ refers to the closeness between a measurement and its accepted value, whereas the term ___ refers to the closeness among a set of measurements.
accuracy precision
Accuracy of which of the following equipment will be analyzed in this experiment: (If you are unsure, consult the lab experiment write-up.) a. 50 mL Graduated Cylinder b. Analytical Balance c. 10 mL Pipet d. Thermometer e. Buret f. 10 mL Graduated Cylinder
ace
analyte-in-this-experiement
acetic-acid
Identify the calculations possible using only 28.02 g/mol as a conversion factor. a. Calculate the grams of N2 in 5.03×10^20 moles of nitrogen molecules b. calculate the grams of N2 in 10.58 liters of nitrogen gas c. calculate the moles of N2 molecules in 4.73 liters of nitrogen gas d. calculate the moles of N2 molecules in 3.94 grams of nitrogen
ad
What are the best practices while sharing a lab balance with other students? a. Brush off any chemical dust around the balance after each use. b. Place samples directly onto the balance. c. Leave a note when you have tared a balance for your glassware. d. Alert your TA or instructor about any issues with the balance.
ad
What is the best way to fill the graduated cylinder EXACTLY to the 10.0 mL marking? a. Observing the meniscus at eye level. b. Over-filling the graduated cylinder, then pouring off excess water until the meniscus is at the 10.0 mL marking. c. Pouring the last bit of water from a beaker d. By adding small amounts of water using a medicine dropper once the meniscus is near the desired volume.
ad
indicator
added to a titration to find the endpoint
All lab participants must remain prepared to use safety equipment in case of emergency. Identify the components of effective preparation. A.) Being familiar with how safety equipment is used B.) Researching alternatives to the safety equipment available in lab C.) Practicing with safety equipment before the start of each lab session D.)Knowing what safety equipment is available E.)Understanding where the safety equipment is located
ade
Solution of an unknown concentration that has another solution slowly added to it
analyte
Safety glasses are required in lab
any time you are in lab
In the experiment Introduction to Chemistry Lab you evaluated several different pieces of glassware. The evaluation involved
attempting to deliver a quantity of water and then determining the actual volume delivered by measuring its mass.
Which procedure cannot be performed on a hot plate, requiring a Bunsen burner instead? a. Heating an isolated solid to dry it b. Heating a crucible to remove water from a hydrate c. Heating water to boiling for a water bath d. Heating a solvent to help the solute dissolve
b
Identify tools that are ideal for cleaning glassware a. Reusable cloths b. Detergent and water c. Brushes d. Steel wool
bc
What should you do every time before you leave the lab? A.) Turn off the lights. B.) Remove your labcoat, if you are wearing one. C.) Wash your hands. D.) Remove your gloves.
bcd
While setting up a beaker to boil a solution on a hot plate, you notice that the stirring is erratic and unstable. What should you do to stabilize the stirring solution? a. Clamp the beaker in place at the edge of the hot plate b. Move the beaker to the center of the hot plate c. Completely turn off the stirring function d. Turn down the stirring speed
bd
determine when to put on disposable gloves for work in the lab
before handling any glassware or chemicals for the experiment
what doe the letters on the NFPA diamond mean
blue health red flammability yellow reactivity d special hazards
Glassware that allows a solution to be precisely and slowly added to another solution
buret
An outlier is identified
by examining the data set to look for a point clearly unlike the others.
Identify the step that is not recommended when responding to an emergency. a. Proceed calmly and listen for instructions. b. Turn off equipment such as Bunsen burners and gas jets. c. Gather your belongings. d. Alert your instructor.
c
When an alarm sounds in the laboratory, it is important to respond ___ and remain ___. Listen for any other instructions, turn off any ___ in use, and be prepared to leave immediately.
calmly quiet equipment
Match each lab incident to the item of PPE that will protect you from it. While pulling an empty beaker off the shelf at the beginning of lab, it slips out of your hand onto the floor.
closed-toed shoes
Determine whether the stopcock should be completely open, partially open, or completely closed for each activity involved with titration. Filling the buret with titrant
completely closed
Determine whether the stopcock should be completely open, partially open, or completely closed for each activity involved with titration. conditioning the buret with titrant
completely closed
Determine whether the stopcock should be completely open, partially open, or completely closed for each activity involved with titration. At the beginning of a titration
completely open
A standard solution has a precisely known ___. It is prepared by dissolving a known mass of ___ and diluting to a precise ___
concentration solute volume
What should you do if you are using a balance that has persistent fluctuations in mass?
contact your TA or instructor to adjust the balance
Elernmeyer Flask function
containing a stirred reaction mixture
Before running a titration, you calculate the expected endpoint. However, when performing the experiment, you pass the expected endpoint with no visible color change. What is the most likely problem with the titration set-up? a. The buret tip is leaking titrant into the analyte b. The analyte solution is being stirred too quickly. c. There was an air bubble in the buret tip. d. There is not enough indicator in the analyte.
d
For which pieces of lab equipment will mass measurements be recorded using the analytical balance? a. Weighing dish b. Rubber stoppers c. Watchglass d. Corks and vial with cap
d
What practice will not help you make an accurate volume reading on a buret at the beginning of a titration? a. Read the volume with the meniscus at eye level. b. Read the volume at the bottom of the meniscus. c. Make sure the meniscus falls within the marked range on the buret d. Make sure that the meniscus starts exactly at 0.00 mL.
d
The equation to calculate density is ___, where D is the density, m is the ___ and v is the ___
d=m/v mass volume
When cleaning a buret, begin by coating the inside with ___. Empty most of it out, then drain the rest by ___ Rinse with ___, then hang upside-down on a buret rack.
detergent solution opening the stopcock deionized water
When the required amount of one solution has been added to the second solution to complete the reaction
endpoint
percent error formula
experimental value-accepted value/accepted value x 100
Identify the safety equipment designed to deal with each emergency listed. chemicals in eyes
eyewash station
true or false Beverages are allowed in lab as long as they are in containers with lids.
false
true or false Chewing gum is okay in the lab as long as you don't blow bubbles.
false
Identify the safety equipment designed to deal with each emergency listed. fire on a person
fire blanket
Identify the equipment best suited for extinguishing each type of fire: clothing fire ___ small benchtop fire ___ large fire on floor ____
fire blanket overturned beaker fire extinguisher
Identify the safety equipment designed to deal with each emergency listed. large fire on the benchtop
fire extinguisher
Identify the safety equipment designed to deal with each emergency listed. cuts or minor burns
first aid kit
If you drop or break glassware in lab, first ______. Then, _______. Finally, place all that material into the ______
get thick gloves or dustpan carefully collect all the broken glassware broken glass container
Match each lab incident to the item of PPE that will protect you from it. While picking up a buret, an unknown solution left by a previous solution drips onto your hand.
gloves
Match each lab incident to the item of PPE that will protect you from it. While checking on a stirring solution, the solution splashes up towards your face.
goggles
which safety equipment will you likely use in a lab
goggles, lab coat, gloves
Determine whether each of the properties described applies to volumetric or graduated glassware. Capable of measuring a range of volumes of liquid ___ Used for applications in which great accuracy is needed ___ Designed to measure one specific volume of liquid ___
graduated volumetric volumetric
Changing gloves often will minimize the spread of chemicals. To properly remove gloves, first, ____ and then, ____ then insert
grasp the exterior of one glove with a gloved hand peel off the first glove a bare finger between the interior edge of the second glove and the skin, and remove the second glove.
Identify the description that applies to the substance represented by each NFPA diamond. blue 2 red 4 yellow 0 white cor
has a flash point below room temperature
A reagent added to the analyte solution that changes color when the reaction is complete
indicator
Match each lab incident to the item of PPE that will protect you from it. While transferring a solution from a flask to a beaker, the solution accidentally spills down the front of the lab bench.
lab coat
According to the experimental procedure, which method will be used to mix the analyte solution while titrating?
magnetic stir bar
graduated cylinder function
measuring out a volume of liquid
convert 7860 feet to miles 7860 feet x (A/B) A. B.
miles feet 1.49 feet
Identify the description that applies to the substance represented by each NFPA diamond. blue 3 red 0 yellow 2 white blank
moderately unstable or reactive
which is the outlier Trial 1 46.44 mL. Trial 2 46.24 mLTrial 3 46.20 mLTrial 4 46.39 mL
none
When you need accurate measurements of chemicals, you can use ___ because ___
only glassware that has been calibrated some volume markings are only estimates.
Identify the description that applies to the substance represented by each NFPA diamond. blue: 3 red: 0 yellow: 0 white: OX
oxidizer not flammable
Determine whether the stopcock should be completely open, partially open, or completely closed for each activity involved with titration. close to the calculated endpoint of a titration
partially open
indicator used
phenolphthalein
What is generally the best approach when liquid from a large reagent bottle is needed in an experiment?
pour some of the reagent from the bottle into a beaker, then use as needed in the procedure.
beaker function
pouring an approximate volume of liquid into a buret
Precision vs. Accuracy
precision is consistency of output whereas accuracy is alignment with the targeted value or goal
Determine the best way to deal with each of the following items that may dangle into the way during lab work. -loose bracelets -flowy sleeves -long earrings -long necklaces -long hair
remove tie back or secure remove remove tie back or secure
Identify the safety equipment designed to deal with each emergency listed. chemicals on clothes
safety shower
Move to the safety shower if you spill hazardous chemicals on your ___. Stand under the shower and ____ the lever. Remove clothing and continue flushing the area for ___
skin or clothing pull 15 minutes
When setting up your experiment, ___is added to the buret and ___ is pipetted into the Erlenmeyer flask. One to two drops of ___ are added to the Erlenmeyer flask along with additional water to bring the total volume to 50 mL before beginning the titration.
sodium hydroxide acetic acid phenolphthalein
the titrant in the lab was
sodium hydrozide
the ___ is the substance that dissolves and is present in a ___ amount in the solution. The ___ is the medium for dissolving and is present in a ___ amount of the solution
solute smaller solvent larger
Identify the description that applies to the substance represented by each NFPA diamond. blue 2 red 3 yellow 0 white blank
stable, has health risks but no special hazards
When heating a solution to boiling on a hot plate, start by ___ . Then, turn the heat to ___ to start. If necessary, ___ after waiting about ten minutes without seeing boiling.
starting and stabilizing the stir function a medium heat setting turn up the heat setting
precision
the ability to repeat a measurement
standardizatoin
the analytical determination of the molarity of the solution
analyte
the chemical species undergoing evaluation in a titration
In a titration, the endpoint is the point at which ___. the equivalence point is the point at which ___
the indicator changes color moles of acid equals moles of base
Under what conditions should a student inform the instructor of a lab injury?
the instructor must be informed of all laboratory injuries
solvent
the major substance of the solution
solute
the minor substance of the solution
stoichiometric point
the point in a titration when enough titrant has been added to react exactly with the substance in solution being titrated
To condition the buret, add a small volume of ___ to the buret and rotate the barrel ___ so that the liquid makes contact with the full inner surface of the barrel. Complete this action ___ and discard each volume in a designated waste container.
the titrant at an angle close to horizontal two more times
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
what is the purpose of stirring a solution while it is being heated
to help evenly distribute throughout the solution
which is the outlier Trial 1 23.11 mL Trial 2 23.20 mLTrial 3 21.22 mLTrial 4 23.17 mL
trial 3
true or false Food items should not be brought into the lab.
true
true or false Tobacco products of all kinds are prohibited in lab.
true
In lab, you may need to evaluate the odor or smell of a chemical. What is the best way to smell a chemical sample?
use your hand to gently waft the smell towards you
36.5
what is the reading
Determine when you should remove your goggles in the lab room.
when everyone in the room is done handling any chemicals or glassware
equivalence point
when the analyte completely reacts with the titrant and no additional titrant is present in the titration solution
end point of titration
when the indicator changes color
How many significant figures are in the number 345?
3
Identify the value of each number presented in scientific notation. 4.65×10^3
4650
A student performed a density experiment in triplicate and recorded the data shown. Calculate the average density (in g/mL) for this experiment. Density Trial 1: 5.08g/mL Trial 2 4.92g/mL Trial 3 5.13g/mL
5.04
Perform the calculation, rounding your answer to the proper number of significant figures. 0.384 g + 5.28 g=
5.66
Mass of weigh boat 1.614 g Mass of weigh boat and sample 8.810 g What is the mass of the solid sample (in g)
7.196
In an experiment, the molar mass of propane was determined to be 47.61 g/mol. The accepted value for the molar mass of propane is 44.10 g/mol. What is the percent error of the experimental value?
7.96
Identify the value of each number presented in scientific notation 7.32×10^6
7320000
When should you start a new chemical waste container in the lab? A.) When the contents of the current container are a couple inches below the brim of the container B.) When the contents of the current container completely fill the container to the brim C.) When you need to dispose of another chemical that is compatible with chemicals in the current container D.) When you accidentally spill chemicals down the side of the current container
A
funnel
A
Choose the best graduated cylinder to make each measurement in a single use. 36 mL of water
a 50 mL graduated cylinder with markings every 10 mL
identify which balance was used to make each mass reading. 4.0000g
a balance with +/- 0.0001g tolerance
identify which balance was used to make each mass reading. 1.230g
a balance with +/- 0.001g tolerance
identify which balance was used to make each mass reading. 6.539g
a balance with +/- 0.001g tolerance
identify which balance was used to make each mass reading. 0.90 g
a balance with +/- 0.01 g tolerance
identify which balance was used to make each mass reading. 5.43g
a balance with +/-g tolerance
aliquot
a carefully measured portion of a solution
solution
a homogeneous mixture of two or more components
standard solution
a solution of known concentration
standard solutions
a solution of known concentration
Which types of signs are posted to convey information about chemical storage? Select one or more: A.)Hazard signs such as "Flammable," "Oxidizer," and "Corrosive" B.) National Fire Protection Association (NFPA) diamond C. Gas Cylinder sign D. Exit sign E. Safety equipment signs such as "Safety Shower" and "Eyewash Station"
ab
Which signs are typically posted in areas of active lab work? A.Chemical storage signs B.Personal protective equipment (PPE) sign C.Sign prohibiting food and drink D.Safety equipment signs
abcd
What purposes can funnels serve in the lab? a. Support for filter paper during a gravity filtration b. Help for transferring solid chemicals from weigh boats c. Change the speed at which a solution drips d. Assistance for pouring liquids into burets
abd
When using a properly stabilized balance, how should you ensure that you get the most accurate mass reading possible? a. Measure the mass of the sample at room temperature b. Lean on the table to steady the balance during reading c. Close the side shields on the balance during reading d. Place the sample on the edge of the balance pan
ac