Q: Convert $$0.00456 to $$scientific notation and state the number of significant figures.

$$4.56 \times 10$$^{-3}$$, 3 significant figures

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 $$45.0\ \mathrm{g}$$ and a volume of $$15.0\ \mathrm{mL}. $$What is its density, and how many significant figures should the answer have?

Accepted Answer

$$3.00\ \mathrm{g/mL}$$, 3 significant figures

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 $$0.00456 to $$scientific notation and state the number of significant figures.

Accepted Answer

$$4.56 	imes 10$$^{-3}$$, 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 noble gas configuration

Question 7

A student adds $$25.0\ \mathrm{g} of $$ethanol (density $$0.789\ \mathrm{g/mL}) to a $$graduated cylinder. What volume, in mL, does the ethanol occupy? (Round to the correct number of significant figures.)

Accepted Answer

$$31.7\ \mathrm{mL}$$

Question 8

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 contains two or more different elements chemically combined

Question 9

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

Accepted Answer

The Bohr model describes electrons in fixed orbits, while the Quantum-Mechanical model describes electrons in orbitals with probability distributions

Question 10

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 11

A sample of water is heated from $$25.0^\circ\mathrm{C} to$$ $$75.0^\circ\mathrm{C}. If $$the mass of water is $$100.0\ \mathrm{g}$$ and the specific heat capacity of water is $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, how much energy (in J) is absorbed? (Use $$q = m c \Delta T$$ and round to the correct number of significant figures.)

Accepted Answer

$$20,900\ \mathrm{J}$$

Question 12

Which of the following best describes an exothermic process?

Accepted Answer

A chemical reaction that releases heat to the surroundings

Question 13

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

Accepted Answer

Al \u003c Mg \u003c Na

Question 14

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 15

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 16

Which of the following molecules is non-polar?

Accepted Answer

Carbon dioxide, $$\mathrm{CO_2$}$$

Question 17

A student needs to convert $$98.6^\circ\mathrm{F} ($$normal human body temperature) to $$^\circ\mathrm{C}. $$Which equation should they use, and what is the correct answer (rounded to the correct number of significant figures)?

Accepted Answer

$$^\circ\mathrm{C} = \frac{5}{9}(98.6 - 32) = 37.0^\circ\mathrm{C}$$

Question 18

Which of the following best explains why fluorine is the most electronegative element?

Accepted Answer

Fluorine has a small atomic radius and a high effective nuclear charge, so it attracts electrons strongly

Question 19

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

Accepted Answer

A Cl symbol surrounded by 8 dots (representing electrons) and a $$-$$ charge written in the upper right

Question 20

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

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