Question

Standard Plate Count Assessment

You want to make lemonade from scratch. This means combining lemon juice from lemons, sugar and water. This is really a dilution problem like the protocol described. The lemon juice is 2 times more concentrated than you want it to be. How would you dilute the lemon juice accordingly? Your answer must include the volumes of lemon juice and water (diluent) that need to be mixed together and also what the total volume will be after the dilution.

1:5 dilution = 1/5 dilution = 1 part sample and 4 parts diluent in a total of 5 parts. If you need 10 ml, final volume, then you need 1/5 of 10 ml = 2 ml sample. To bring this 2 ml sample up to a total volume of 10 ml, you must add 10 ml - 2 ml = 8 ml diluent.

A. Your friend wants to perform 1/10 and 1/100 dilutions of the concentrated lemon juice. The person does not understand what this means and asks you for help. How would you explain to her what this means? How should she perform these dilutions?

1/10: _____ ml lemon juice    and ______ ml water

1/100: _____ ml lemon juice    and ______ ml water

A. You take 1 mL of concentrate juice and add 9 mL of water. What dilution did you make here?

B. You take 10 mL of concentrated juice and add 90 mL of water.What dilution did you make here?

C. Were your answers in A and B the same or different? Explain your answer.

Answer 1

1/10: ___1__ ml lemon juice    and ___9___ ml water

1/100: __1___ ml lemon juice    and ___99___ ml water

A. You take 1 mL of concentrate juice and add 9 mL of water.  What dilution did you make here?

Answer: 1:10 or (1/10)

B. You take 10 mL of concentrated juice and add 90 mL of water.What dilution did you make here?

Answer: 10:100 = 1:10 or(1/10)

C. Same because the taken solute amount is same in both case

in 1st case, 1 ml in 9 ml means in total 10 ml of solution 1 ml of solute is present so 1/10

In 2nd case, 10 ml in 90 ml means 10 ml in 100 ml of solution so concentration is same 10/100 = 1/10