CHEM 123 Final Exam 2026 | Lab final Exam | All
Questions and Correct Answers | Already Graded
A+ | Verified Answers | Just Released
What is something you should never do when pipetting? ---------CORRECT
ANSWER-----------------never pipet from a reagent stock bottle or volumetric flask
(could contaminate stock solution/break neck of the volumetric flask)
How to deliver solution from pipette ---------CORRECT ANSWER------------------
quickly transfer the filled pipette to Erlenmeyer flask (keep index-finger tightly
over pipette to maintain suction)
- drain the pipette (touch tip to side of Erlenmeyer flask, release finger and allow
to drain by gravity & hold the pipette to the side of Erlenmeyer flask for another
10 seconds)
**Do not blow/shake out small amount of solution remaining in the tip of the
pipette**
How to clean the burette ---------CORRECT ANSWER------------------ use clean funnel
over the sink & add 5-10mL of deionized water with the stopcock closed
- hold in horizontal position and roll to coat insides with water
- drain water through tip by opening the stopcock
- repeat 2x
- close stopcock again and use clean funnel & add 5-10mL of solution into burette
,- hold horizontally and coat sides of burette with solution & drain through
stopcock into sink or waste beaker
How to fill the burette ---------CORRECT ANSWER------------------ close stopcock &
use funnel to fill burette to 0 mark & clamp burette at bench with waste beaker
under the tip
- open stopcock to drain some solution to ensure the burette has no air bubbles
(not essential to fill exactly to 0.00)
- fill the burette, remove funnel, touch tip of burette to inside wall of a beaker to
remove any drops on the tip
How to read the burette ---------CORRECT ANSWER------------------ read at lowest
point of meniscus (make sure eyes are parallel)
- use white card/paper behind the burette below meniscus to see
- record meniscus/volume of burette to 2 decimal places
How to Operate the burette ---------CORRECT ANSWER------------------ record initial
volume of burette to 2 decimal places
- lower burette tip into erlenmeyer flask that has the solution to be titrated
- open stopcock slowly with left hand & adjust flow rate by using thumb & 2
fingers around the stopcock
- turn on magnetic stirrer to low speed (avoids solution splashing up walls of the
flask
- wait about 30 seconds & record final volume of the burette to 2 decimal places
, Why do we perform iodometric titrations ---------CORRECT ANSWER-----------------
to find the concentration of an unknown by mixing it with a solution of known
concentration
What are the 4 (general) steps of an iodometric titration? ---------CORRECT
ANSWER-----------------combine solutions, reach endpoint, calculate, determine the
concentration of the unknown
What reaction takes place during an iodometric titration? ---------CORRECT
ANSWER-----------------oxidation-reduction reaction
What is used as the oxidizing agent in an iodometric titration? ---------CORRECT
ANSWER-----------------potassium iodate
Top-loading balance ---------CORRECT ANSWER------------------ used for prepwork
and obtains a mass to the nearest +/-0.1g (uncertainty of +/- 0.05g)
- used prior to analytical balance
Analytical balance ---------CORRECT ANSWER------------------ used to determine a
precise mass to the nearest +/- 0.0001 g
Questions and Correct Answers | Already Graded
A+ | Verified Answers | Just Released
What is something you should never do when pipetting? ---------CORRECT
ANSWER-----------------never pipet from a reagent stock bottle or volumetric flask
(could contaminate stock solution/break neck of the volumetric flask)
How to deliver solution from pipette ---------CORRECT ANSWER------------------
quickly transfer the filled pipette to Erlenmeyer flask (keep index-finger tightly
over pipette to maintain suction)
- drain the pipette (touch tip to side of Erlenmeyer flask, release finger and allow
to drain by gravity & hold the pipette to the side of Erlenmeyer flask for another
10 seconds)
**Do not blow/shake out small amount of solution remaining in the tip of the
pipette**
How to clean the burette ---------CORRECT ANSWER------------------ use clean funnel
over the sink & add 5-10mL of deionized water with the stopcock closed
- hold in horizontal position and roll to coat insides with water
- drain water through tip by opening the stopcock
- repeat 2x
- close stopcock again and use clean funnel & add 5-10mL of solution into burette
,- hold horizontally and coat sides of burette with solution & drain through
stopcock into sink or waste beaker
How to fill the burette ---------CORRECT ANSWER------------------ close stopcock &
use funnel to fill burette to 0 mark & clamp burette at bench with waste beaker
under the tip
- open stopcock to drain some solution to ensure the burette has no air bubbles
(not essential to fill exactly to 0.00)
- fill the burette, remove funnel, touch tip of burette to inside wall of a beaker to
remove any drops on the tip
How to read the burette ---------CORRECT ANSWER------------------ read at lowest
point of meniscus (make sure eyes are parallel)
- use white card/paper behind the burette below meniscus to see
- record meniscus/volume of burette to 2 decimal places
How to Operate the burette ---------CORRECT ANSWER------------------ record initial
volume of burette to 2 decimal places
- lower burette tip into erlenmeyer flask that has the solution to be titrated
- open stopcock slowly with left hand & adjust flow rate by using thumb & 2
fingers around the stopcock
- turn on magnetic stirrer to low speed (avoids solution splashing up walls of the
flask
- wait about 30 seconds & record final volume of the burette to 2 decimal places
, Why do we perform iodometric titrations ---------CORRECT ANSWER-----------------
to find the concentration of an unknown by mixing it with a solution of known
concentration
What are the 4 (general) steps of an iodometric titration? ---------CORRECT
ANSWER-----------------combine solutions, reach endpoint, calculate, determine the
concentration of the unknown
What reaction takes place during an iodometric titration? ---------CORRECT
ANSWER-----------------oxidation-reduction reaction
What is used as the oxidizing agent in an iodometric titration? ---------CORRECT
ANSWER-----------------potassium iodate
Top-loading balance ---------CORRECT ANSWER------------------ used for prepwork
and obtains a mass to the nearest +/-0.1g (uncertainty of +/- 0.05g)
- used prior to analytical balance
Analytical balance ---------CORRECT ANSWER------------------ used to determine a
precise mass to the nearest +/- 0.0001 g
