CR Chapter 7 Measurement Review

What is the scale on this graduated cylinder? Each mark represents -

• 1 mL per line

• .2 mL per line

• .5 mL per line

• .1 mL per line

Answer explanation

The scale on this graduated cylinder represents 1 mL per line because there are ten lines between 30 mL and 40 mL.

Where do we read the level of liquid?

• The highest point the liquid touches

• The bottom of the meniscus

• Half way between, we make an educated guess and round it

• We just take a guess

Answer explanation

The graduated cylinder is calibrated so that reading the bottom of the meniscus, when viewed at eye level, will give accurate results. Viewing the meniscus at any angle other than eye level will give inaccurate results.

Which value below best expresses the volume measured in this beaker to the correct number of significant figures?

• 48 mL

• 48.2 mL

• 48.25 mL

• 50 mL

Answer explanation

The correct choice is 48 mL because this beaker has increments (lines) worth 10 mL so the uncertain digit is in the ones place. You must do one uncertain digit when measuring in chemistry.

The diameter of a carbon atom is 0.000000000154 m. What is this number expressed in scientific notation?

• 1.54 x 10¹² m

• 1.54 x 10^-12 m

• 1.54 x 10¹⁰ m

• 1.54 x 10^-10 m

Answer explanation

The diameter of a carbon atom is 1.54 x 10^-10 m because the decimal place must be moved 10 times and the exponent is negative because the measurement is a very small fraction of 1.

Express 23400 in proper scientific notation. 

• 2.34 x 10⁴

• 2.3 x 10³

• 2.30 x 10⁵

• 2.34 x 10³

Answer explanation

To express 23400 in scientific notation, move the decimal point to the left until there is only one non-zero digit to the left. The correct choice is 2.34 x 10⁴.

Calculate the answer to the following problem and round the final answer to the correct number of sig figs:
2.78 x 11.70 =

• 32.526

• 33

• 32.53

• 32.5

Answer explanation

To multiply 2.78 by 11.70, we count the number of significant figures in each number. 2.78 has 3 significant figures and 11.70 has 4 significant figures. The answer should have the same number of significant figures as the least precise number, which is 3. Rounding 32.526 to 3 significant figures gives us 32.5.

Calculate the answer to the following problem and round the final answer to the correct number of sig figs:

24.567 + 0.04478 =

• 24.61178

• 24.612

• 24.610

• 24.61

Answer explanation

To round the sum to the correct number of sig figs, we look at the least precise number with the least number of decimal places, which is 24.567. So the answer needs 3 decimal places.

Determine the number of sig figs in the following measurement:

0.00300 nm

• 3 sf

• 6 sf

• 1 sf

• 5 sf

Answer explanation

The measurement 0.00300 nm has 3 significant figures because leading zeros are not counted as a significant figure while trail zeros after a decimal point are considered as a significant figure.

What is the length of the screw?

• 5.11 cm

• 6.01 cm

• 5 cm

• 5.101 cm

Answer explanation

The length of the screw is 5.11 cm because this ruler has increments of 0.1 cm, the uncertain digit it called in the hundredths place.

You must call an uncertain digit whenever measuring in chemistry.

Place the following steps in order for measuring the volume of a marble using water displacement.

• Record the final volume of the graduated cylinder.

• Place enough water in the graduated cylinder to cover the marble.

• Subtract the difference of the final volume from the starting volume.

• Gently roll place the marble in the graduated cylinder.

• Record the starting volume of water in the graduated cylinder.

Answer explanation