Q: A graduated cylinder contains water at the 25.0 mL mark. After adding a metal object, the water rises to 32.5 mL. If the mass of the metal is 60.0 g, what is its density?

$$\text{Density} = \frac{60.0\ \text{g}}{32.5\ \text{mL} - 25.0\ \text{mL}} = \frac{60.0\ \text{g}}{7.5\ \text{mL}} = 8.0\ \text{g/mL}$$

Q: Which of the following is the correct conversion for 250 milliliters to liters?

$$250\ \text{mL} \times \frac{1\ \text{L}}{1000\ \text{mL}} = 0.25\ \text{L}$$

Q: A thermometer reads 25.0 $$^\circC. $$What is this temperature in Kelvin?

$$25.0 + 273.15 = 298.15\ \text{K}$$

Q: A 50.0 g piece of metal at 100.0 $$^\circC is $$placed in 100.0 g of water at 25.0 $$^\circC. $$The final temperature is 30.0 $$^\circC. If $$the specific heat of water is $$4.18\ \text{J/g} \cdot ^\circ\text{C}$$, what is the specific heat of the metal? (Assume no heat loss to the environment.)

$$q_{\text{water}} = 100.0\ \text{g} \times 4.18\ \text{J/g} \cdot ^\circ\text{C} \times (30.0 - 25.0) = 2,090\ \text{J}$$ $$q_{\text{metal}} = -2,090\ \text{J}$$ $$-2,090 = 50.0\ \text{g} \times c \times (30.0 - 100.0)$$ $$-2,090 = 50.0 \times c \times (-70.0)$$ $$-2,090 = -3,500c$$ $$c = 0.597\ \text{J/g} \cdot ^\circ\text{C}$$

Q: A mixture contains 5.0 g of salt and 45.0 g of sand. What is the mass percent of salt in the mixture?

$$\text{Mass percent} = \frac{5.0\ \text{g}}{5.0\ \text{g} + 45.0\ \text{g}} \times 100\% = 10\%$$

Question 1

Which part of a Bunsen burner is primarily responsible for controlling the amount of air that mixes with the gas before combustion?

Accepted Answer

The collar (air intake)

Question 2

A student is using a Bunsen burner and notices a yellow, sooty flame. What adjustment should be made to achieve a hotter, blue flame?

Accepted Answer

Open the air intake to allow more oxygen

Question 3

Which of the following best describes the difference between filtration and decantation?

Accepted Answer

Filtration uses a filter to separate solids from liquids, while decantation involves pouring off a liquid from settled solids.

Question 4

When graphing experimental data, which variable is plotted on the x-axis?

Accepted Answer

Independent variable

Question 5

A student records the following masses: 12.34 g, 12.3 g, and 12.345 g. How many significant figures should the average be reported to?

Accepted Answer

3 significant figures

Question 6

A graduated cylinder contains water at the 25.0 mL mark. After adding a metal object, the water rises to 32.5 mL. If the mass of the metal is 60.0 g, what is its density?

Accepted Answer

$$	ext{Density} = \frac{60.0\ 	ext{g}}{32.5\ 	ext{mL} - 25.0\ 	ext{mL}} = \frac{60.0\ 	ext{g}}{7.5\ 	ext{mL}} = 8.0\ 	ext{g/mL}$$

Question 7

Which of the following is the correct conversion for 250 milliliters to liters?

Accepted Answer

$$250\ 	ext{mL} 	imes \frac{1\ 	ext{L}}{1000\ 	ext{mL}} = 0.25\ 	ext{L}$$

Question 8

A thermometer reads 25.0 $$^\circC. $$What is this temperature in Kelvin?

Accepted Answer

$$25.0 + 273.15 = 298.15\ 	ext{K}$$

Question 9

Which of the following best describes the difference between precision and accuracy?

Accepted Answer

Precision refers to how close measurements are to each other, while accuracy refers to how close measurements are to the true value.

Question 10

A 50.0 g piece of metal at 100.0 $$^\circC is $$placed in 100.0 g of water at 25.0 $$^\circC. $$The final temperature is 30.0 $$^\circC. If $$the specific heat of water is $$4.18\ 	ext{J/g} \cdot ^\circ	ext{C}$$, what is the specific heat of the metal? (Assume no heat loss to the environment.)

Accepted Answer

$$q_{	ext{water}} = 100.0\ 	ext{g} 	imes 4.18\ 	ext{J/g} \cdot ^\circ	ext{C} 	imes (30.0 - 25.0) = 2,090\ 	ext{J}$$
$$q_{	ext{metal}} = -2,090\ 	ext{J}$$
$$-2,090 = 50.0\ 	ext{g} 	imes c 	imes (30.0 - 100.0)$$
$$-2,090 = 50.0 	imes c 	imes (-70.0)$$
$$-2,090 = -3,500c$$
$$c = 0.597\ 	ext{J/g} \cdot ^\circ	ext{C}$$

Question 11

Which of the following is an example of a green chemistry principle applied in the laboratory?

Accepted Answer

Using water as a solvent instead of an organic solvent

Question 12

Which of the following best defines an electrolyte?

Accepted Answer

A substance that conducts electricity when dissolved in water

Question 13

A solution turns red litmus paper blue and has a pH of 12. Which of the following best describes the solution?

Accepted Answer

It is a basic solution

Question 14

A mixture contains 5.0 g of salt and 45.0 g of sand. What is the mass percent of salt in the mixture?

Accepted Answer

$$	ext{Mass percent} = \frac{5.0\ 	ext{g}}{5.0\ 	ext{g} + 45.0\ 	ext{g}} 	imes 100\% = 10\%$$

Question 15

Which of the following is the best practice when recording data in a laboratory notebook?

Accepted Answer

Record all observations and data in ink, including mistakes crossed out with a single line

Question 16

A student needs to prepare 250 mL of a 0.10 M NaCl solution. How many grams of NaCl are required? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$0.10\ 	ext{mol/L} 	imes 0.250\ 	ext{L} = 0.025\ 	ext{mol}$$
$$0.025\ 	ext{mol} 	imes 58.44\ 	ext{g/mol} = 1.46\ 	ext{g}$$

Question 17

Which of the following safety rules is most important when heating a substance in a test tube?

Accepted Answer

Point the open end of the test tube away from yourself and others

Question 18

A student is asked to separate a mixture of sand, salt, and iron filings. Which sequence of separation techniques would be most effective?

Accepted Answer

Add water, use a magnet to remove iron, filter to separate sand, evaporate water to recover salt

Question 19

A student is reading the volume in a graduated cylinder. The bottom of the meniscus is at 36.7 mL. Which is the correct way to record this measurement?

Accepted Answer

36.7 mL

Introduction to Chemistry Lab Midterm Study Guide

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