Question 1

Which of the following best describes why it is important to record the temperature of water when measuring its volume for density calculations?

Accepted Answer

Because the temperature affects the density of water, which is needed for accurate calculations.

Question 2

A student measures the mass of a dry 50 mL graduated cylinder as 45.000 g. After adding water, the mass is 95.000 g. What is the mass of the water added?

Accepted Answer

$$95.000\ \mathrm{g} - 45.000\ \mathrm{g} = 50.000\ \mathrm{g}$$

Question 3

When reading the volume of a liquid in a graduated cylinder, what is the correct technique?

Accepted Answer

Read the bottom of the meniscus at eye level.

Question 4

A student uses a 100 mL beaker, a 50 mL graduated cylinder, a 50 mL volumetric flask, and a 10 mL syringe to measure 50 mL of water. Which tool is expected to provide the most accurate measurement?

Accepted Answer

50 mL volumetric flask

Question 5

A solid object is placed in a graduated cylinder containing 30.0 mL of water. The water level rises to 38.5 mL. What is the volume of the object?

Accepted Answer

$$38.5\ \mathrm{mL} - 30.0\ \mathrm{mL} = 8.5\ \mathrm{mL}$$

Question 6

If the mass of an object is 21.4 g and its volume (measured by water displacement) is 8.5 mL, what is its density?

Accepted Answer

$$\frac{21.4\ \mathrm{g}}{8.5\ \mathrm{mL}} = 2.52\ \mathrm{g/mL}$$

Question 7

Which of the following is the best reason for repeating the water displacement measurement multiple times and averaging the results?

Accepted Answer

To minimize random errors and improve accuracy.

Question 8

A student records the mass of a beaker as 120.00 g and the mass of the beaker with water as 170.00 g. If the student accidentally spills some water before weighing, what effect does this have on the calculated density of water?

Accepted Answer

The calculated density will be lower than the true value.

Question 9

Why is it important to include an estimated digit when recording measurements from analog devices like graduated cylinders?

Accepted Answer

It reflects the uncertainty and precision of the measurement.

Question 10

Which of the following is an acceptable way to discuss an experimental error in your post-lab report?

Accepted Answer

We spilled our sample, which means our yield will be much lower than expected.

Question 11

A student uses a 10 mL syringe to measure water and finds a percent error of 2%, while the 100 mL beaker has a percent error of 15%. What conclusion can be drawn?

Accepted Answer

The syringe is more accurate than the beaker.

Question 12

Which of the following best explains why you should never put chemicals directly on the balance pan?

Accepted Answer

To prevent contamination and damage to the balance.

Question 13

In hydrostatic weighing, why is it important that the object (or person) is completely submerged in water?

Accepted Answer

To ensure the entire volume is measured for accurate density calculation.

Question 14

A student calculates the density of an unknown object as $$2.50\ \mathrm{g/mL}$$, but the accepted value is $$2.70\ \mathrm{g/mL}. $$What is the percent error?

Accepted Answer

$$\frac{|2.70 - 2.50|}{2.70} 	imes 100\% = 7.41\%$$

Question 15

Which of the following is the correct formula for density?

Accepted Answer

$$	ext{Density} = \frac{	ext{Mass}}{	ext{Volume}}$$

Question 16

If you refill your beaker with water during an experiment, what must you do to ensure accurate results?

Accepted Answer

Record the new temperature of the water.

Methods of Measurement in Chemistry: Accuracy, Density, and Laboratory Practice

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