Q: A sample contains 0.250 L of a solution. Convert this volume to milliliters (mL).

$$0.250\ \text{L} \times \frac{1000\ \text{mL}}{1\ \text{L}} = 250\ \text{mL}$$

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

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

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 dissolved in water.

Question 2

A student measures the mass of a sample three times and records the following values: 5.12 g, 5.13 g, and 5.11 g. The true mass is 5.50 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 of iron to rust when exposed to oxygen.

Question 4

Which of the following best represents the Law of Conservation of Energy?

Accepted Answer

$$\Delta E_{system} + \Delta E_{surroundings} = 0$$

Question 5

A sample contains 0.250 L of a solution. Convert this volume to milliliters (mL).

Accepted Answer

$$0.250\ 	ext{L} 	imes \frac{1000\ 	ext{mL}}{1\ 	ext{L}} = 250\ 	ext{mL}$$

Question 6

Which of the following is an example of a physical change?

Accepted Answer

Boiling water to produce steam.

Question 7

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 8

Which of the following best describes the difference between an atom and an ion?

Accepted Answer

An ion is an atom that has gained or lost electrons, resulting in a net charge.

Question 9

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

Accepted Answer

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

Question 10

A scientist needs to separate a mixture of sand and salt. Which method would be most effective?

Accepted Answer

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

Question 11

Which of the following best explains why mass is conserved in a chemical reaction?

Accepted Answer

Atoms are rearranged but not created or destroyed during a chemical reaction.

Question 12

Which of the following is a transition metal?

Accepted Answer

Iron (Fe)

Question 13

A student is asked to calculate the percent composition of oxygen in $$	ext{H}_2	ext{O}. $$Which of the following is the correct calculation?

Accepted Answer

$$\frac{16.00}{2.02 + 16.00} 	imes 100\% = 88.8\%$$

Question 14

Which of the following best describes a period on the periodic table?

Accepted Answer

A horizontal row of elements.

Question 15

Which of the following is a correct statement about the scientific method?

Accepted Answer

It involves making observations, forming a hypothesis, conducting experiments, and drawing conclusions.

Question 16

Which of the following is a correct conversion factor to convert grams to kilograms?

Accepted Answer

$$1\ 	ext{kg} = 1000\ 	ext{g}$$

Question 17

Which of the following best describes a chemical change?

Accepted Answer

Silver tarnishing when exposed to air.

Question 18

Which of the following is a property of metals?

Accepted Answer

They are good conductors of electricity.

Question 19

Which of the following best describes the process of nuclear fission?

Accepted Answer

A heavy nucleus splits into two lighter nuclei, releasing energy.

Question 20

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

Accepted Answer

Observation, hypothesis, experiment, conclusion.

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

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