Question

Calculate the percentage error likely to arise in an experiment if 1mL, 5mL, and 10mL pipets are used for transfer and each pipet contains 5 drops of water adhering to the inside of the barrel. A single drop of water has a volume of approximately 0.05mL.

Answer 1

Answer on question #61762, Chemistry, General Chemistry

Calculate the percentage error likely to arise in an experiment if 1mL, 5mL, and 10mL pipets are used for transfer and each pipet contains 5 drops of water adhering to the inside of the barrel. A single drop of water has a volume of approximately 0.05mL.

Solution:

First, determine the amount of volume that remains inside the pipettes:

$$(5 \text{ drops}) \times \left[ \frac{(0.05 \text{ mL})}{(1 \text{ drop})} \right] = 0.25 \text{ mL}$$

The error is determined simply by dividing this number of volumes by the volume of the pipette:

1-mL pipette:

$$\text{error} = \left[ \frac{(0.25 \text{ mL})}{(1.00 \text{ mL})} \right] \times 100\% = 25\%$$

5-mL pipette:

$$\text{error} = \left[ \frac{(0.25 \text{ mL})}{(5.00 \text{ mL})} \right] \times 100\% = 5\%$$

10-mL pipette:

$$\text{error} = \left[ \frac{(0.25 \text{ mL})}{(10.00 \text{ mL})} \right] \times 100\% = 2.5\%$$

Answer: error = 25% (if 1mL), error = 5% (if 5mL), error = 2.5% (if 10mL)

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