Question 1

Which of the following statements best distinguishes a scientific theory from a scientific law?

Accepted Answer

A scientific law describes a consistent relationship observed in nature, while a scientific theory explains the underlying reasons for those relationships.

Question 2

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

Accepted Answer

Burning a piece of magnesium ribbon in air to form magnesium oxide.

Question 3

A sample of water is heated from $$25\ ^\circ\mathrm{C} to$$ $$75\ ^\circ\mathrm{C}. $$What is the temperature change in Kelvin?

Accepted Answer

$$50\ \mathrm{K}$$

Question 4

Which of the following best describes the difference between an element and a compound?

Accepted Answer

An element consists of only one type of atom, while a compound consists of two or more different elements chemically bonded together.

Question 5

A student measures the mass of a sample three times and gets values of 2.51 g, 2.50 g, and 2.52 g. The true mass is 2.80 g. Which statement best describes the measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 6

Which of the following is the correct formula for the ionic compound formed between magnesium and nitrate?

Accepted Answer

$$\mathrm{Mg(NO_3$)_2}$$

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

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of carbon dioxide. How many moles of carbon dioxide are present?

Accepted Answer

$$0.5$$ moles

Question 9

Which of the following best describes the result of Rutherford’s gold foil experiment?

Accepted Answer

Most alpha particles passed through the foil, but some were deflected at large angles, indicating a small, dense, positively charged nucleus.

Question 10

Which of the following is a correct statement about the law of definite proportions?

Accepted Answer

A given compound always contains the same proportion of elements by mass.

Question 11

Which of the following is the correct name for $$\mathrm{P_2O_5}$$?

Accepted Answer

Diphosphorus pentoxide

Question 12

A 10.0 mL sample of ethanol has a mass of 7.89 g. What is the density of ethanol in $$\mathrm{g/mL}$$?

Accepted Answer

$$0.789\ \mathrm{g/mL}$$

Question 13

Which of the following is a property of a crystalline solid?

Accepted Answer

It has a regular, repeating arrangement of particles.

Question 14

Which of the following is the correct empirical formula for hydrogen peroxide?

Accepted Answer

$$\mathrm{HO}$$

Question 15

Which of the following best describes a cation?

Accepted Answer

An atom or molecule that has lost one or more electrons and has a positive charge.

Question 16

Which of the following is a correct conversion between Celsius and Kelvin?

Accepted Answer

$$K = ^\circ\mathrm{C} + 273.15$$

Question 17

Which of the following is a correct statement about Avogadro’s number?

Accepted Answer

It is the number of particles in one mole, $$6.022 	imes 10$$^{23}$$.

Question 18

Which of the following is the correct name for $$\mathrm{$$FeCl_3$$}$$?

Accepted Answer

Iron(III) chloride

Question 19

A sample contains 0.250 moles of sodium chloride. How many formula units of sodium chloride are present?

Accepted Answer

$$1.51 	imes 10$$^{23}$$

Question 20

Which of the following best describes a polyatomic ion?

Accepted Answer

A charged species composed of two or more atoms covalently bonded together.

CHEM 111 Exam 1 Study Guide: Atoms, Molecules, and Chemical Foundations

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