Question 1

Which of the following best describes a chemical, according to the definition used in chemistry?

Accepted Answer

A substance with a definite composition, such as water or carbon dioxide.

Question 2

A student measures the mass of a sample as 0.00450 g. How many significant figures does this measurement have?

Accepted Answer

3

Question 3

Which of the following is the correct scientific notation for the number 0.000312?

Accepted Answer

$$3.12 	imes 10$$^{-4}$$

Question 4

A sample of gold has a mass of 19.3 g and a volume of 1.00 cm$$^3. $$What is the density of gold, and how many significant figures should the answer have?

Accepted Answer

$$19.3\ \mathrm{g/cm^3$}$$, 3 significant figures

Question 5

Which of the following is a heterogeneous mixture?

Accepted Answer

A salad with lettuce, tomatoes, and cucumbers

Question 6

Which of the following changes is a chemical change?

Accepted Answer

A piece of iron rusting in moist air

Question 7

A patient is given 250 mg of a medication. How many grams is this? (Use the correct number of significant figures.)

Accepted Answer

$$0.250\ \mathrm{g}$$

Question 8

Which of the following statements about the Bohr and Quantum-Mechanical models of the atom is correct?

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 elements is most likely to form a $$2^+$$ ion, and why?

Accepted Answer

Magnesium, because it is an alkaline earth metal and tends to lose two electrons.

Question 10

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

Accepted Answer

Electrons fill degenerate orbitals singly before pairing up.

Question 11

A sample contains two isotopes of chlorine: $$^{35}\mathrm{Cl} (75.8$$% abundance, mass = 34.97 u) and $$^{37}\mathrm{Cl} (24.2$$% abundance, mass = 36.97 u). What is the average atomic mass of chlorine? (Round to 2 decimal places.)

Accepted Answer

$$35.45\ \mathrm{u}$$

Question 12

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

Accepted Answer

Elements in the same group have similar chemical properties because they have the same number of valence electrons.

Question 13

Which of the following molecules is non-polar?

Accepted Answer

Carbon dioxide ($$\mathrm{CO}_2)$$

Question 14

Which of the following best describes an exothermic process?

Accepted Answer

A chemical reaction that releases energy to the surroundings, such as combustion.

Question 15

A beaker contains 100.0 g of water at $$25.0\ ^\circ\mathrm{C}. $$How much energy (in joules) is required to raise the temperature to $$35.0\ ^\circ\mathrm{C}$$? (Specific heat of water $$= 4.18\ \mathrm{J/g\cdot ^\circ C})$$

Accepted Answer

$$4,180\ \mathrm{J}$$

Question 16

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have delocalized electrons that can move freely throughout the structure.

Question 17

Which of the following is the correct electron configuration for a neutral atom of oxygen ($$Z=8$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^4$$

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 pairs of atoms is most likely to form an ionic bond?

Accepted Answer

Sodium and chlorine

Question 20

Which of the following statements about electronegativity is correct?

Accepted Answer

Fluorine is the most electronegative element because it has a high effective nuclear charge and a small atomic radius.

Intro to Chemistry Midterm Exam Study Guide – Step-by-Step Guidance

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