Question21 Complete the following statement by selecting the most correct answer from the options below. When practicing accurate pipetting techniques: Select one alternative: pushing the plunger all the way down to the second stop allows the complete volume of liquid to be expelled from the tip. changing tips between different solutions to be transferred is not necessary. holding the pipette at an angle (between horizontal and vertical) permits the solution to be drawn up more accurately. placing the end of the tip further down into the liquid when drawing up the solution to be transferred allows more effective mixing. the smallest volume you can accurately pipette is approximately 1% of the maximum volume. ResetMaximum marks: 1 Flag question undefined

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BlackTom AI · Accepted Answer

Question: Complete the following statement by selecting the most correct answer from the options below. When practicing accurate pipetting techniques: Select one alternative.

Option 1: pushing the plunger all the way down to the second stop allows the complete volume of liquid to be expelled from the tip. This is correct because on most adjustable micropipettes, the second stop is designed to expel all residual liquid from the tip, ensuring accurate delivery of the set volume.

Option 2: changing tips between different solutions to be transferred is not necessary. This is false because cross-contamination can occur if tips are reused between different solutions; standard practice requires changing tips for each separate transfer.

Option 3: holding the pipette at an angle (between horizontal and vertical) permits the solution to be drawn up more accurately. This is inaccurate because drawing up liquid is best done with the pipette held upright (near-vertical) to prevent air intake and to maintain volume accuracy; tilting reduces accuracy.

Option 4: placing the end of the tip further down into the liquid when drawing up the solution to be transferred allows more effective mixing. This is misleading: lowering the tip into the liquid can cause aspiration of more liquid than intended, introduce air bubbles, or cause inconsistent volumes; proper mixing is achieved by gentle resuspension or pipette operation, not by deeper tip placement.

Option 5: the smallest volume you can accurately pipette is approximately 1% of the maximum volume. This statement is not universally true; the reliable accuracy depends on the specific pipette model and calibration, and many models have best accuracy in a defined range, not a fixed 1% of max for all cases.

In summary, option 1 accurately reflects the correct use of the second stop to expel all of the liquid from the tip, while the other options describe practices that would compromise accuracy, safety, or cross-contamination control in pipetting.

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