Question 1

Which of the following best describes a chemical property of matter?

Accepted Answer

The ability of iron to rust when exposed to oxygen

Question 2

A sample of a substance has a mass of $$12.5\ \mathrm{g}$$ and a volume of $$4.50\ \mathrm{cm^3$}. $$What is its density, rounded to the correct number of significant figures?

Accepted Answer

$$2.8\ \mathrm{g/cm^3$}$$

Question 3

Which of the following statements about the scientific method is correct?

Accepted Answer

A hypothesis is a tentative explanation that can be tested by experiments.

Question 4

Which of the following is a heterogeneous mixture?

Accepted Answer

Salad dressing with oil and vinegar

Question 5

Convert $$3.45 	imes 10^4$ to standard notation and state the number of significant figures.

Accepted Answer

$$34,500$$ with $$3$$ significant figures

Question 6

Which of the following best explains why metals tend to form cations?

Accepted Answer

Metals have low ionization energies and lose electrons to achieve a stable electron configuration.

Question 7

A student adds $$50.0\ \mathrm{g} of $$water at $$25.0^\circ\mathrm{C} to a $$metal sample. The metal cools from $$100.0^\circ\mathrm{C} to$$ $$25.0^\circ\mathrm{C}$$, releasing $$3,150\ \mathrm{J} of $$heat. What is the specific heat capacity $$c of $$the metal? Use $$q = m c \Delta T$$ and round to the correct number of significant figures.

Accepted Answer

$$0.900\ \mathrm{J/g\cdot ^\circ C}$$

Question 8

Which of the following best describes the difference between the Bohr model and the Quantum-Mechanical model of the atom?

Accepted Answer

The Bohr model describes electrons in fixed orbits, while the Quantum-Mechanical model describes electrons in probability clouds called orbitals.

Question 9

Which of the following is the correct electron configuration for a neutral atom of magnesium ($$Z=12$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$

Question 10

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 11

Which of the following best describes an exothermic process?

Accepted Answer

A chemical reaction that releases heat to the surroundings

Question 12

A solution is prepared by dissolving $$5.00\ \mathrm{g} of $$NaCl in $$95.0\ \mathrm{g} of $$water. Which of the following best describes the resulting mixture?

Accepted Answer

A homogeneous mixture

Question 13

Which of the following is the correct order of increasing atomic size for the elements Na, Mg, and Al?

Accepted Answer

$$\mathrm{Al} \u003c \mathrm{Mg} \u003c \mathrm{Na}$$

Question 14

Which of the following best explains why water ($$\mathrm{H_2O}) is a $$polar molecule?

Accepted Answer

Water has polar O–H bonds and a bent molecular shape, resulting in a net dipole moment.

Question 15

Which of the following is the correct Lewis structure for a chloride ion ($$\mathrm{Cl^-}$$)?

Accepted Answer

A Cl atom surrounded by 8 dots (electrons) and a $$-$$ charge written as a superscript

Question 16

Which of the following best describes Hund’s rule as it applies to electron configurations?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing up.

Question 17

A sample of gold has two naturally occurring isotopes: $$^{197}\mathrm{Au} ($$abundance $$100.0\%) $$and $$^{198}\mathrm{Au} ($$abundance $$0.0\%). $$What is the average atomic mass of gold?

Accepted Answer

$$197\ \mathrm{u}$$

Question 18

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their valence shell.

Question 19

Which of the following is the correct formula to convert a temperature from Celsius to Kelvin?

Accepted Answer

$$K = ^\circ C + 273.15$$

Question 20

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have a full valence shell of electrons, making them stable.

Introduction to Chemistry: Midterm Exam Study Guide – Step-by-Step Guidance

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