Q: A sample contains 3.0 moles of sodium chloride (NaCl). How many grams of NaCl are present? ($$\text{Molar mass of NaCl} = 58.44\ \text{g/mol})$$

$$3.0 \times 58.44 = 175.32\ \text{g}$$

Q: A student needs to convert 250 milliliters (mL) to liters (L). What is the correct conversion?

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

Q: Which of the following is the correct nuclear equation for alpha decay of $$^{238}_{92}\text{U}$$?

$$^{238}_{92}\text{U} \$$rightarrow ^{234}$$_{90}\text{Th} $$+ ^{4}$$_{2}\alpha$$

Q: A solution is prepared by dissolving 5.00 g of NaCl in enough water to make 250 mL of solution. What is the concentration in g/L?

$$\frac{5.00\ \text{g}}{0.250\ \text{L}} = 20.0\ \text{g/L}$$

Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture in which the composition is uniform throughout, such as salt water.

Question 2

A student measures the mass of a sample three times and gets values of 2.50 g, 2.51 g, and 2.49 g. The true mass is 2.80 g. Which statement best describes the accuracy and precision of these measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Which of the following is a chemical property?

Accepted Answer

Ability to react with oxygen to form rust.

Question 4

A sample contains 3.0 moles of sodium chloride (NaCl). How many grams of NaCl are present? ($$	ext{Molar mass of NaCl} = 58.44\ 	ext{g/mol})$$

Accepted Answer

$$3.0 	imes 58.44 = 175.32\ 	ext{g}$$

Question 5

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 6

Which method would be most appropriate to separate a mixture of sand and salt?

Accepted Answer

Dissolve the mixture in water, filter to remove sand, then evaporate the water to recover salt.

Question 7

Which of the following is NOT a pure substance?

Accepted Answer

Air

Question 8

A student needs to convert 250 milliliters (mL) to liters (L). What is the correct conversion?

Accepted Answer

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

Question 9

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 10

Which of the following is the correct nuclear equation for alpha decay of $$^{238}_{92}	ext{U}$$?

Accepted Answer

$$^{238}_{92}	ext{U} \$$rightarrow ^{234}$$_{90}	ext{Th} $$+ ^{4}$$_{2}\alpha$$

Question 11

Which of the following is a physical change?

Accepted Answer

Melting of ice into water.

Question 12

A solution is prepared by dissolving 5.00 g of NaCl in enough water to make 250 mL of solution. What is the concentration in g/L?

Accepted Answer

$$\frac{5.00\ 	ext{g}}{0.250\ 	ext{L}} = 20.0\ 	ext{g/L}$$

Question 13

Which of the following best explains why nuclear fission is used in power plants?

Accepted Answer

It releases a large amount of energy by splitting heavy nuclei.

Question 14

Which of the following is the correct order of steps in the scientific method?

Accepted Answer

Observation, hypothesis, experiment, analysis, conclusion.

Question 15

Which of the following is a transition metal?

Accepted Answer

Iron (Fe)

Question 16

A radioactive isotope has a half-life of 10 years. If you start with 80 grams, how much will remain after 30 years?

Accepted Answer

$$80\ 	ext{g} ightarrow 40\ 	ext{g} ightarrow 20\ 	ext{g} ightarrow 10\ 	ext{g}$$

Question 17

Which of the following particles is emitted during beta decay?

Accepted Answer

An electron ($$^{0}_{-1}\beta)$$

Question 18

Which of the following is the correct definition of an ion?

Accepted Answer

An atom or molecule with a net electric charge due to the loss or gain of electrons.

Question 19

Which of the following is a correct application of the Law of Conservation of Energy in a chemical reaction?

Accepted Answer

The total energy before and after the reaction remains the same.

Question 20

Which of the following best describes the difference between mass and weight?

Accepted Answer

Mass is the amount of matter in an object; weight is the force exerted by gravity on that mass.

Introduction to Chemistry: Key Concepts, Measurement, Atomic Structure, and Nuclear Chemistry

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