CHM 117 Final review (Lab 1)

Determine whether each quantity is a measured value or an exact value.

2 avocados- Exact 1 ft = 12 in- Exact 3 teacups- Exact 18 meters- Measured 144 grams of sugar- Measured 2 cups of milk- Measured

Identify the pieces of glassware that are most effective for accurate solution preparation.

Volumetric pipe Volumetric flask

Identify which balance was used to make each mass reading.

0.90 g: +- 0.01 g tolerance 6.539 g: +--.001g tolerance 5.43 g: +-0.01 g tolerance 1.230 g: +-0.001 g tolerance 4.0000 g: +-0.0001 g tolerance

Identify effective techniques for accurate pipet use.

1) Do not let liquid enter the pipet bulb or pump 2) Measure liquid by aligning the meniscus with the volume line

When describing the uncertainty of a measurment, the term _____ refers to the closeness between a measurement and its accepted value, whereas the term _____ refers to the closeness among a set of measurements

1) accuracy 2) precision

In order to use a pipet, place a ______ at the top of the pipet. Use this object to fill the pipet such that the ______ of the liquid is even with the volume line. Release the liquid, touching the tip of the pipet to the side of the container if necessary to release the last drop ______ the pipet tip

1) bulb or pump 2) meniscus 3) outside

What is the correct reading of the volume in the pictured buret?

39.95 mL

Determine whether each of the errors listed affects the accuracy of pipets, or can lead to the contamination of pipets.

Air bubbles are present as the liquid is drawn up into the pipet and dispensed- accuracy The liquid level in a pipet is read from the top of the curve rather than the meniscus- accuracy After the liquid is drained from the pipet, the final drop is pushed through with the pipet bulb- accuracy Pipets are washed with detergent and then put to use immediately- contamination The pipet is not cleaned thoroughly between uses- contamination

Determine whether each of the properties described applies to volumetric or graduated glassware.

Capable of measuring a range of volumes of liquid- graduated Designed to measure one specific volume of liquid- volumetric Used for applications in which great accuracy is needed- volumetric

How do you determine the last digit in any measured number on a non-digital instrument?

Estimate one digit past the smallest precisely known digit or marking.

Why do you need to record the temperature when making careful volume measurements of water?

The density of water depends on its temperature