Q: Calculate the molecular weight of water ($\mathrm{H}_2\mathrm{O}$) using the atomic masses: H = 1.0 amu, O = 16.0 amu.

$2 \times 1.0 + 16.0 = 18.0$ amu

Q: A sample contains $4.0$ g of carbon. How many atoms of carbon are present? (Atomic mass of C = $12.0$ g/mol, Avogadro's number $= 6.022 \times 10^{23}$ atoms/mol)

$\frac{4.0}{12.0} \times 6.022 \times 10^{23} = 2.0 \times 10^{23}$ atoms

Q: Which of the following is the correct mole-to-atom conversion factor for oxygen atoms?

$1$ mol O $= 6.022 \times 10^{23}$ atoms O

Q: How many moles of hydrogen are present in $10.0$ g of acetic acid ($\mathrm{C}_2\mathrm{H}_4\mathrm{O}_2$)? (Molar mass of acetic acid $= 60.0$ g/mol)

$\frac{10.0}{60.0} \times 4 = 0.67$ mol H

Q: Which of the following is the correct molar mass for glucose ($\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$) given C = 12.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol?

$6 \times 12.0 + 12 \times 1.0 + 6 \times 16.0 = 180.0$ g/mol

Question 1

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 2

A neutral atom of sodium (Na) has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

$23 - 11 = 12$ neutrons

Question 3

Which of the following best describes an isotope?

Accepted Answer

Atoms with the same number of protons but different numbers of neutrons

Question 4

What is the correct symbol for an atom with 29 protons, 36 neutrons, and 29 electrons?

Accepted Answer

$^{65}\mathrm{Cu}$

Question 5

Which of the following statements about ions is correct?

Accepted Answer

An ion is formed when an atom gains or loses electrons

Question 6

Calculate the molecular weight of water ($\mathrm{H}_2\mathrm{O}$) using the atomic masses: H = 1.0 amu, O = 16.0 amu.

Accepted Answer

$2 	imes 1.0 + 16.0 = 18.0$ amu

Question 7

How many atoms of oxygen are present in one molecule of acetic acid ($\mathrm{C}_2\mathrm{H}_4\mathrm{O}_2$)?

Accepted Answer

2

Question 8

A sample contains $4.0$ g of carbon. How many atoms of carbon are present? (Atomic mass of C = $12.0$ g/mol, Avogadro's number $= 6.022 	imes 10^{23}$ atoms/mol)

Accepted Answer

$\frac{4.0}{12.0} 	imes 6.022 	imes 10^{23} = 2.0 	imes 10^{23}$ atoms

Question 9

Which of the following is the correct mole-to-atom conversion factor for oxygen atoms?

Accepted Answer

$1$ mol O $= 6.022 	imes 10^{23}$ atoms O

Question 10

A neutral atom of sulfur ($\mathrm{S}$) has an atomic number of 16. If it gains two electrons, what is its resulting charge?

Accepted Answer

$2-$

Question 11

Which statement best explains why atomic mass is not always a whole number?

Accepted Answer

Atomic mass is a weighted average of all naturally occurring isotopes

Question 12

How many moles of hydrogen are present in $10.0$ g of acetic acid ($\mathrm{C}_2\mathrm{H}_4\mathrm{O}_2$)? (Molar mass of acetic acid $= 60.0$ g/mol)

Accepted Answer

$\frac{10.0}{60.0} 	imes 4 = 0.67$ mol H

Question 13

Which of the following is a correct classification for the element calcium ($\mathrm{Ca}$)?

Accepted Answer

Alkaline Earth Metal

Question 14

A molecule of glucose ($\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$) contains how many total atoms?

Accepted Answer

$6 + 12 + 6 = 24$ atoms

Question 15

Which of the following is the correct formula weight for sodium chloride ($\mathrm{NaCl}$) given Na = 23.0 amu and Cl = 35.5 amu?

Accepted Answer

$23.0 + 35.5 = 58.5$ amu

Question 16

If an atom has 15 protons, 16 neutrons, and 18 electrons, what is its charge and classification?

Accepted Answer

Charge: $3-$, Classification: Ion

Question 17

Which of the following is the correct molar mass for glucose ($\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$) given C = 12.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol?

Accepted Answer

$6 	imes 12.0 + 12 	imes 1.0 + 6 	imes 16.0 = 180.0$ g/mol

Question 18

Which of the following best describes the relationship between atomic number and mass number?

Accepted Answer

Mass number = atomic number + number of neutrons

Question 19

A compound contains 2 moles of hydrogen and 1 mole of oxygen. What is the empirical formula?

Accepted Answer

$\mathrm{H}_2\mathrm{O}$

Chap 2Atoms and Molecules: Structure, Properties, and Calculations

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