A student calibrated a Beral pipet while holding it at two different angles. Whe

Question

A student calibrated a Beral pipet while holding it at two different angles. When she held the pipe horizontally, it delivered an average of 30 drops mL^-1. When she held it vertically, it delivered average of 28 drops mL^-1. Calculate the volume, in liters, of one drop delivered from the horizontal pipet. Calculate the volume, in liters, of one drop delivered from the cal pipet. Explain why it is crucial in this experiment that the pipet always be held at the same angle when counting the number of drops being delivered.

Explanation / Answer

(1) From the horizontal pipet 30 drops = 1 mL

so, 1 drop =0.0333 mL = 3.333 x 10-5 L (1L=1000mL)

(2) From the vertical pipet 28 drops = 1 mL

so, 1 drop =0.035714 mL = 3.5714 x 10-5 L (1L=1000mL)

(3) You can see for two cases vertical & horizontal 1 drop is not same. For other angle it will be further different. Hence, while doing experiment the pipet always be held at the same angle when counting the number of drops being delivered otherwise for different angle value of 1 drop will be different and it leads to an error in analysis.

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