Question

re, contact your admin about your Office plan Lab Homework- Please submit handwritten before class. 1. Write three ways that you can use the factor that was used to dilute a sample. 2. Dilution Factors Sample 0.1ml 99ml 0.1 m 9.9 ml1ml9mL 1ml9m Tube #2 Tube #2 Tube 83 Tube 84 Tube 85 What is the dilution factor for tub #17 a) 10 b) 10 c) 10 d) 10 e 1:10 what is the overall dilution factor for tube #37 a) 10 b) 104 c) 10 d) 10 e)10 what is the overal diluation factor alhe way to tube Ps)y7 a) 1:10b) 10 c) 10 d) 10 e) 10 3. One of your fellow classmates got sick after drinking coca cola (with ice) from a soda fountain at a local fast food restaurant. He claims that toilet water is cleaner than the ice cubes that are dispensed from the machine at the restaurant. What organisms do you think causes contamination of ice dispensers? How could you test the water and conclude which water is "cleaner"? Show your work by creating appropriate dilution schemes a. b. MacBook Air

Answer 1

1.

• Using C1V1 = C2V2

To make a fixed amount of a dilute solution from a stock solution, you can use the formula: C1V1 = C2V2 where:

• V1 = Volume of stock solution needed to make the new solution
• C1 = Concentration of stock solution
• V2 = Final volume of new solution
• C2 = Final concentration of new solution

Using Dilution Factors

To make a dilute solution without calculating concentrations, you can rely on a derivation of the above formula:
(Final Volume / Solute Volume) = Dilution Factor (can also be used with mass)

Step Dilutions

If the dilution factor is larger than the final volume needed, or the amount of stock is too small to be pipetted, one or more intermediary dilutions may be required. Use the formula: Final DF = DF1 * DF2 * DF3 etc., to choose your step dilutions such that their product is the final dilution.

2.

• b) 0.1 ml of stock in 9.9 ml of diluent, so it can be like 1mL of stock in 100 mL of diluent so =10^-2
• d) answer: 10^-5 in the tube #3
• d) Answer: 10^-7 in the tube #5

3. Bacteria

collect both samples and perform serial dilutions for each sample, then spread the samples in 2 different nutrient media containing petri dish, observed after 24 hours you will find a number of colonies formed in toilet water sample which was spread.