Think of two or three changes that could be implemented to improve the procedure

Question

Think of two or three changes that could be implemented to improve the procedure if you were to perform a follow-up experiment to your serial dilutions. Word them in the form of a hypothesis (“If ______was done/changed then it would be expected that.” [what would happen?]). Perhaps you’re curious about investigating how different materials would work or how you could change part of the procedure that gave you problems, but you must consider what the results of the change might be (i.e. you don’t have to be right, but you must have a reason for your hypothesis. This is for a dilution Kool-Aid experiment.

Explanation / Answer

Ans. Seral dilution is the gradual dilution of the concentrated (stock) solution into two or more successive diluted steps.

The following hypotheses can be put to follow-up the experiment f serial dilution-

I. If dilution was done then it would be expected that the concentration of final (diluted) solution would be less than that of respective stock solution.

For any dilution step, the relation between volumes and concentration of the two solutions (stock and diluted solution) can be correlated using the equation-

                                    C1V1 = C2V2                        - equation 1

C1= Concentration, and V1= volume of stock solution      ;( stock)

C2= Concentration, and V2 = Vol. of final solution – for particular dilution step

Check: At any point, the concentration of a diluted solution can NOT be greater than the concentration of its respective stock solution.

II. If correct serial dilution was done then it would be expected that the concentration of last solution (result of last dilution step) would be equal to the concentration of stock solution multiplied by total dilution factor (total dilution from first to last step of dilution).

Check: Suppose you diluted the stock solution by a dilution factor of (1: 1000) in 10 dilution steps – a dilution factor of 1: 1000 means that 1.0 mL of the stock solution was diluted to 1000.0 mL during successive dilutions in 10 steps.

Let the concentration of original stock solution be C1.

Total dilution factor (from first to last dilution step) = 1: 1000

Then,

Concentration of last diluted solution = [Original stock] x total dilution factor

= C1 x (1: 1000)

= C1/ 1000 = 0.001 C1

If you performed the seral dilution correctly, then the concentration of last diluted solution must 1/1000 times that of original stock. If it’s NOT, then errors might have occurred in one or more dilution steps.

Similarly, the second hypothesis can be used to check the validity of perfect serial dilution (error can be accepted to a certain limit).

III. If correct serial dilution was done then it would be expected that the concentration of each solution (result of last dilution step) would be lower than the its respective stock solution and greater than its successive diluted solution.

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