Question 1

Which of the following best describes a hypothesis in the scientific method?

Accepted Answer

A tentative explanation that can be tested by experiments.

Question 2

Which of the following is a heterogeneous mixture?

Accepted Answer

Sand and iron filings

Question 3

A student observes that a metal changes color when heated. Which type of property is being observed?

Accepted Answer

Chemical property

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 5

Calculate the molar mass of $$\mathrm{C_2H_6O} ($$ethanol). (Atomic masses: C = 12.01, H = 1.01, O = 16.00)

Accepted Answer

$$\mathrm{46.08\ g/mol}$$

Question 6

Which of the following is an example of a redox reaction?

Accepted Answer

Combustion of methane: $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$

Question 7

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of $$\mathrm{$$CO_2$$}$$. How many moles of $$\mathrm{$$CO_2$$}$$ are present?

Accepted Answer

$$0.25$$ mol

Question 8

Which of the following best explains why sodium (Na) is more reactive than magnesium (Mg)?

Accepted Answer

Sodium has a lower ionization energy.

Question 9

Which of the following electron configurations represents a noble gas?

Accepted Answer

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

Question 10

Which of the following molecules has a bent molecular geometry according to VSEPR theory?

Accepted Answer

$$\mathrm{H_2O}$$

Question 11

Which of the following solutions is a buffer?

Accepted Answer

A solution of acetic acid and sodium acetate

Question 12

Which of the following best describes the Pauli Exclusion Principle?

Accepted Answer

No two electrons in an atom can have the same set of four quantum numbers.

Question 13

Which of the following is the correct balanced equation for the combustion of propane ($$\mathrm{C_3H_8}$$)?

Accepted Answer

$$\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}$$

Question 14

Which of the following statements about acids and bases is correct?

Accepted Answer

An acid increases the concentration of $$\mathrm{H^+}$$ ions in solution.

Question 15

Which of the following best describes the trend in atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases from left to right.

Question 16

A radioactive isotope has a half-life of 10 years. How much of a 100 g sample remains after 30 years?

Accepted Answer

12.5 g

Question 17

Which of the following is a correct Lewis structure for $$\mathrm{NH_3$}$$?

Accepted Answer

Nitrogen with three single bonds to hydrogen and one lone pair

Question 18

Which of the following best describes the relationship between electronegativity and bond polarity?

Accepted Answer

A bond between atoms with similar electronegativities is nonpolar.

Question 19

Which of the following is the correct formula for calcium phosphate?

Accepted Answer

$$\mathrm{Ca_3$(PO_4$)_2}$$

Question 20

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

Accepted Answer

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

Introduction to Chemistry: Comprehensive Study Guide

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