CHEM 101 Lab Final Exam Prep Pack | Experiments Review,
Practical Questions & Detailed Answers
1. When should you NOT wear gloves in the lab setting?
a. When weighing our reagents at the balances
b. When entering in data on your laptop
c. When handling clean glassware
d. When writing notes on scratch paper using a pen and paper - answers-b and d
*Also, should not wear gloves when opening doors
2. General glove rules - answers-- you should never reuse gloves
- dispose of gloves if they are heavily contaminated
- dispose of gloves if they are torn
- dispose of gloves in the glove hazardous waste container
- gloves must be worn at all times while handling chemicals or glassware
- do not wear gloves outside of lab
3. You make a solution of 0.1M NaOH and accidentally spill the solution, covering
your gloved hand and onto your arm. Your wrist was exposed, and the solution
came into direct contact with your skin. What should you do? - answers-let your
TA know and wash your skin under running water for at least 15 minutes
4. When should goggles be worn in lab? - answers-The whole time you are in lab
5. You are taking an evening laboratory session and want to bring a snack to help
you make it through the evening. When should you be allowed to have food at the
bench top in the lab?
a. If the experimental work is over and cleaned up
b. At the beginning because it is dinner time and being a student is exhausting.
c. Only if the food remains in the students backpack while at the bench top.
d. Never.
e. Never, unless you have a tendency to become hypoglycemic, then you are
allowed to eat at the bench to prevent health issues. - answers-d. Never
6. Accuracy - answers-A measure of how close a measurement is to the true
value of the quantity measured.
, 7. Precision - answers-A measure of how close a series of measurements are to
one another.
8. Systematic error arises from a flaw in the equipment or in the experimental
design. This type of error can be detected and corrected. It leads to predictable
results. Provide several examples. - answers-- a scale that is improperly
calibrated and always reads 2.3 grams heavier than the object actually is
- a stretched out measuring tape that always reads values lower than the true
value.
9. Random error arises from uncontrolled, often uncontrollable, variables in an
experiment which has equal chance of being positive and negative. This type of
error cannot be detected or corrected for. It leads to unpredictable results.
Results will likely cluster around true value. Provide several examples. - answers-
- wind speed might speed up or slow down at unpredictable times
- any measurement between 2 markings because different people will read the
measurement differently
10. EXP 1: Why does ice float in water? - answers-Ice is less dense than water
because the negatively charged oxygen atoms repel one another due to
Hydrogen bonding. After 4 C (40 F), water begins losing density.
11. EXP 2: You measure NaOH by difference using an analytical balance. The
initial mass of the NaOH bottle is 5.042g. After removing the NaOH, the bottle
mass is 4.812g. What is the mass of the NaOH you are using? (use correct sig
figs) - answers-0.230 g
12. Mass is measured to _____ significant figs - answers-4
13. Volume is measured to _____ significant figures - answers-3
14. Density equation - answers-mass/volume
15. Find the density of liquid CO2. Remember that 1 mL=1 cm^3.
Mass - 55.05g, volume - 10mL - answers-55.05g/10mL = 5.505 g/mL
16. Find the density of Dry Ice (solid CO2). Determine whether the solids will sink
of float when put into liquid CO2. Remember that 1 mL = 1 cm^3.
Mass - 15.62g, 10cm^3 - answers-15.62g/10cm^3 = 1.562g/cm^3
17. Find the density of ice. Determine whether the solids will sink or float when
put into liquid CO2. Remember that 1 mL = 1 cm^3.
Mass - 9.34g, 10cm^3 - answers-9.34g/10cm^3 = 0.934g/cm^3
16. Mean equation - answers-add up all the data and divide by # of data points
Practical Questions & Detailed Answers
1. When should you NOT wear gloves in the lab setting?
a. When weighing our reagents at the balances
b. When entering in data on your laptop
c. When handling clean glassware
d. When writing notes on scratch paper using a pen and paper - answers-b and d
*Also, should not wear gloves when opening doors
2. General glove rules - answers-- you should never reuse gloves
- dispose of gloves if they are heavily contaminated
- dispose of gloves if they are torn
- dispose of gloves in the glove hazardous waste container
- gloves must be worn at all times while handling chemicals or glassware
- do not wear gloves outside of lab
3. You make a solution of 0.1M NaOH and accidentally spill the solution, covering
your gloved hand and onto your arm. Your wrist was exposed, and the solution
came into direct contact with your skin. What should you do? - answers-let your
TA know and wash your skin under running water for at least 15 minutes
4. When should goggles be worn in lab? - answers-The whole time you are in lab
5. You are taking an evening laboratory session and want to bring a snack to help
you make it through the evening. When should you be allowed to have food at the
bench top in the lab?
a. If the experimental work is over and cleaned up
b. At the beginning because it is dinner time and being a student is exhausting.
c. Only if the food remains in the students backpack while at the bench top.
d. Never.
e. Never, unless you have a tendency to become hypoglycemic, then you are
allowed to eat at the bench to prevent health issues. - answers-d. Never
6. Accuracy - answers-A measure of how close a measurement is to the true
value of the quantity measured.
, 7. Precision - answers-A measure of how close a series of measurements are to
one another.
8. Systematic error arises from a flaw in the equipment or in the experimental
design. This type of error can be detected and corrected. It leads to predictable
results. Provide several examples. - answers-- a scale that is improperly
calibrated and always reads 2.3 grams heavier than the object actually is
- a stretched out measuring tape that always reads values lower than the true
value.
9. Random error arises from uncontrolled, often uncontrollable, variables in an
experiment which has equal chance of being positive and negative. This type of
error cannot be detected or corrected for. It leads to unpredictable results.
Results will likely cluster around true value. Provide several examples. - answers-
- wind speed might speed up or slow down at unpredictable times
- any measurement between 2 markings because different people will read the
measurement differently
10. EXP 1: Why does ice float in water? - answers-Ice is less dense than water
because the negatively charged oxygen atoms repel one another due to
Hydrogen bonding. After 4 C (40 F), water begins losing density.
11. EXP 2: You measure NaOH by difference using an analytical balance. The
initial mass of the NaOH bottle is 5.042g. After removing the NaOH, the bottle
mass is 4.812g. What is the mass of the NaOH you are using? (use correct sig
figs) - answers-0.230 g
12. Mass is measured to _____ significant figs - answers-4
13. Volume is measured to _____ significant figures - answers-3
14. Density equation - answers-mass/volume
15. Find the density of liquid CO2. Remember that 1 mL=1 cm^3.
Mass - 55.05g, volume - 10mL - answers-55.05g/10mL = 5.505 g/mL
16. Find the density of Dry Ice (solid CO2). Determine whether the solids will sink
of float when put into liquid CO2. Remember that 1 mL = 1 cm^3.
Mass - 15.62g, 10cm^3 - answers-15.62g/10cm^3 = 1.562g/cm^3
17. Find the density of ice. Determine whether the solids will sink or float when
put into liquid CO2. Remember that 1 mL = 1 cm^3.
Mass - 9.34g, 10cm^3 - answers-9.34g/10cm^3 = 0.934g/cm^3
16. Mean equation - answers-add up all the data and divide by # of data points
