Quantitation for Lab Practice Questions

Juanita analyzed a sample of creek water for bacterial concentration. She performed serial dilutions then placed 1 ml of each sample onto agar plates. She counted 234 colonies on the plate where the 1:1,000 dilution was plated. What is the concentration of bacteria in the creek?

Mathematical Equivalence

ON

Tags

NGSS.HS-LS2-1

NGSS.HS-LS2-4

Bill Ney analyzed the tap water in his home through membrane filtration. He filtered 100 ml through a membrane filter. The membrane was then placed onto an agar plate. The next day Bill counted 98 colonies on the plate. What is the concentration of bacteria in Bill’s water?

Mathematical Equivalence

ON

Rae asked her students to prepare 18 ml of a 1:6 dilution of bleach. Describe how 18 ml of this dilution would be prepared.

• 3 ml bleach and 15 ml water

• 2 ml bleach and 16 ml water

• 1 ml bleach and 17 ml water

• 12 ml bleach and 6 ml water

Noel analyzed pond water for bacterial concentration. She performed serial dilutions and plated 0.5 ml of each dilution onto agar plates. The next day she counted colonies. The 1:10,000 plate contained 84 colonies. What is the bacterial concentration of the pond water?

Mathematical Equivalence

ON

Tags

NGSS.HS-LS2-4

Jack suspected that the swimming pool water contained a high level of bacteria. Jack diluted the swimming pool water using serial dilutions. Jack placed 1 ml of the 1:10,000 dilution on an agar plate. The next day Jack counted 235 colonies on the plate. What is the total concentration of bacteria in the pool?

Mathematical Equivalence

ON

Anna took one milliliter of raw milk at the dairy farm and added it to 9 ml sterile water. She then took one milliliter of that dilution and added it to an additional test tube containing 9 ml sterile water. Then, she took 1 milliliter of that dilution and added it to 9 ml sterile water. Anna took 1 ml from the most diluted test tube and placed that on an agar plate. The next day Anna counted 133 CFU on the agar plate. What is the bacterial concentration of the raw milk at the farm?

Mathematical Equivalence

ON

Carlos needs to prepare a 1:5 dilution of concentrated soap. He needs to prepare 45 mls of the diluted solution. Explain how to prepare the diluted soap solution.

• 8 ml soap and 37 ml water

• 9 ml soap and 36 ml water

• 5 ml soap and 40 ml water

• 40 ml soap and 5 ml water

PeiChun wanted to analyze the bacterial concentration of bottled water. She filtered 100 ml of the bottled water through a sterile membrane filter. The membrane was then aseptically placed on an agar plate and incubated overnight. After incubation, PeiChun counted 325 CFU on the membrane filter. What is the bacterial concentration of the bottled water?

Mathematical Equivalence

ON