$$\text{Average atomic mass} = \sum (\text{isotope mass} \times \text{fractional abundance})$$

$$\text{Number of protons} = \text{atomic number}$$

Question 1

Which subatomic particle determines the identity of an element and its position on the periodic table?

Accepted Answer

Proton

Question 2

A neutral atom of chlorine has an atomic number of 17 and a mass number of 35. How many neutrons does it contain?

Accepted Answer

18

Question 3

Which formula correctly represents the calculation of average atomic mass using natural abundances?

Accepted Answer

$$	ext{Average atomic mass} = \sum (	ext{isotope mass} 	imes 	ext{fractional abundance})$$

Question 4

Which of the following is a molecular compound?

Accepted Answer

CO$$_2$$

Question 5

What is the electron geometry and bond angle for a molecule with three electron groups and no lone pairs?

Accepted Answer

Trigonal planar, 120$$^\circ$$

Question 6

Which of the following Lewis structures is correct for water (H$$_2O$$)?

Accepted Answer

O with two single bonds to H and two lone pairs

Question 7

Which intermolecular force is present in all molecules, regardless of their composition?

Accepted Answer

Dispersion (London) forces

Question 8

A molecule of ammonia (NH$$_3) $$has which molecular geometry and is it polar?

Accepted Answer

Trigonal pyramidal, polar

Question 9

Which of the following statements about ionic compounds is correct?

Accepted Answer

They consist of positive and negative ions held together by electrostatic forces.

Question 10

Which of the following is the correct Lewis structure for carbon dioxide (CO$$_2$$)?

Accepted Answer

O=C=O with two lone pairs on each O

Question 11

Which type of intermolecular force is responsible for the high boiling point of water?

Accepted Answer

Hydrogen bonding

Question 12

How many valence electrons are present in a molecule of methane (CH$$_4$$)?

Accepted Answer

12

Question 13

Which of the following best describes the difference between alkanes and alkenes?

Accepted Answer

Alkanes contain only single bonds, while alkenes contain at least one double bond.

Question 14

Which of the following is a correct condensed structural formula for propane?

Accepted Answer

CH$$_3CH$_2CH$_3$$

Question 15

Which of the following functional groups is present in acetic acid?

Accepted Answer

Carboxylic acid

Question 16

A sample contains 80% $$^{35}Cl ($$mass = 34.97 amu) and 20% $$^{37}Cl ($$mass = 36.97 amu). What is the average atomic mass of chlorine?

Accepted Answer

35.37 amu

Question 17

Which of the following molecules is nonpolar despite having polar bonds?

Accepted Answer

CO$$_2$$

Question 18

Which of the following is the correct electron configuration for a neutral oxygen atom?

Accepted Answer

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

Question 19

Which of the following best explains why ionic compounds conduct electricity when dissolved in water?

Accepted Answer

The ions are free to move and carry charge.

Question 20

Which of the following is the correct formula for calculating the number of protons in an ion?

Accepted Answer

$$	ext{Number of protons} = 	ext{atomic number}$$

Introduction to Chemistry: Exam 2 Study Guide

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