2B1 Chemistry

Question 1

Define:

mole concept

Answer 1

A counting unit for particles.

1 mole = 6.022 x 10²³ particles, converting atomic-scale quantities to macroscopic ones. This number is often referred to as Avogadro’s number, and is used as a constant in many chemical equations.

Question 2

How many particles are in 1 mole?

Answer 2

6.022 x 10²³

1 mole is often represented with the term mol.

Question 3

Define:

Molar mass

Answer 3

The mass of one mole of a substance (g/mol).

(Photo credit: GeeksforGeeks)

It is numerically equivalent to the atomic or molecular mass in atomic mass units (amu).

Question 4

True or False:

The mole concept relates moles to mass.

Answer 4

True

The mole concept is used to convert between the number of particles and the mass of a substance.

Question 5

What is the unit for molar mass?

Answer 5

g/mol

Molar mass is measured in grams per mole (g/mol), which indicates the mass of one mole of a substance.

Question 6

What is the formula for calculating molar mass?

Answer 6

∑ (Atomic Mass of Element × Number of Atoms of Element)

Add the atomic mass of each element, multiplied by the number of atoms of that element in the formula, to find the molar mass.

Question 7

How do you convert moles to grams?

Answer 7

Multiply moles by molar mass.

Molar mass (g/mol) represents the mass of one mole of a substance.

For example, to convert 2 moles of water (H₂O) to grams, multiply 2 moles by 18.016 g/mol (the molar mass of H₂O), giving you 36.032 grams.

Question 8

How many moles are in 144 grams of carbon, given that the molecular mass of carbon is 12g/mol.?

Answer 8

12 moles

144 grams divided by 12g/mol results in 12 moles.

Question 9

What is percent composition?

Answer 9

The mass percentage of each element in a compound.

Percent composition is used to determine the relative amounts of each element in a compound, which is helpful in stoichiometric calculations and analyzing chemical formulas.

For example, in NaCl, the percent composition of Na is 39.34%, and Cl is 60.66%.

Question 10

How is percent composition calculated?

Answer 10

(Mass of element / Total molar mass) x 100.

For H₂O, the mass of hydrogen is 2 g and the total mass of water is 18 g, so hydrogen’s percent composition is (2 / 18) × 100 = 11.1%.

Question 11

True or False:

Percent composition is used in the food industry for nutrient labeling on food packaging.

Answer 11

True

Percent composition helps calculate the nutrient content in food, such as proteins, fats, and carbohydrates, assisting consumers in maintaining their daily nutrient intake.

Question 12

What does percent composition help determine in the construction industry?

Answer 12

Material purity and mixture ratios.

Ensuring proper proportions of materials like cement and sand is vital for the strength and durability of concrete.

Question 13

What should the sum of the percent compositions of all elements in a compound equal?

Answer 13

100%.

The total percent composition confirms the accuracy of the compound’s molecular formula.

Question 14

What is Avogadro’s number?

Answer 14

6.022×10 ^23 particles per mole.

This number is a fundamental constant that defines the number of atoms, molecules, or particles in one mole of any substance, enabling conversions between the molecular and macroscopic scale.

Question 15

Fill in the blank:

Avogadro’s number converts moles to _______.

Answer 15

particles

Avogadro’s number provides a direct relationship between moles and individual particles (atoms, molecules, ions).

Question 16

What is a chemical formula?

Answer 16

A representation of a compound’s elements.

It shows the types and quantities of atoms present in a compound. For instance, H₂O represents water, with two hydrogen atoms and one oxygen atom.

Question 17

What does a structural formula show?

Answer 17

The arrangement of atoms and bonds.

Structural formulas represent how atoms are bonded in a molecule and can include electron-dot diagrams or line structures to show shared electron pairs, like the bond between H and O in H₂O.

Question 18

What is the empirical formula?

Answer 18

The simplest whole-number ratio of elements in a compound.

It simplifies the ratio of elements. For glucose (C₆H₁₂O₆), the empirical formula is CH₂O, representing the simplest form of the compound’s elemental composition.

Question 19

What is a molecular formula?

Answer 19

The formula that shows the actual number of atoms of each element in a molecule.

The molecular formula may be the same as or a multiple of the empirical formula.

For example, the molecular formula of glucose is C₆H₁₂O₆, while its empirical formula is CH₂O, which represents the simplest ratio of elements.

Question 20

True or False:

The empirical and molecular formulas are always the same.

Answer 20

False

The empirical formula shows the simplest ratio of atoms, while the molecular formula provides the actual number of atoms.

For glucose, the molecular formula is C₆H₁₂O₆, but the empirical formula is CH₂O.

Question 21

What is the chemical formula for water?

Answer 21

H₂O

Water consists of two hydrogen atoms bonded to one oxygen atom, with the formula H₂O.

Question 22

Fill in the blank:

The chemical formula for calcium sulfate is _________.

Answer 22

CaSO₄

Calcium sulfate consists of one calcium ion (Ca²⁺) and one sulfate ion (SO₄²⁻), giving it the formula CaSO₄.

Question 23

True or False:

NaCl has two sodium atoms.

Answer 23

False

NaCl is an ionic compound composed of one sodium atom (Na) and one chlorine atom (Cl), forming a 1:1 ratio, not two sodium atoms.

Question 24

What happens to nitrogen dioxide when heated?

Answer 24

It forms nitrogen monoxide and oxygen.

When heated, nitrogen dioxide (NO₂) decomposes into nitrogen monoxide (NO) and oxygen gas:
2NO₂ → 2NO + O₂. This reaction is reversible, and NO₂ reforms when the gas cools.

Question 25

# Define: Chemical compound

Answer 25

A **substance** containing atoms of at least two elements. ## Footnote Chemical compounds are formed when atoms of different elements bond together, either covalently or ionically. These compounds have fixed compositions, like NaCl or H₂O.

Question 26

What are the four **common** types of chemical formulas?

Answer 26

* Molecular Formula * Condensed Formula * Structural Formula * Empirical Formula ## Footnote Molecular formulas give exact atom counts, while empirical formulas show the simplest ratios. Condensed formulas group atoms together, and structural formulas show bonding.

Question 27

How is a condensed formula **different** from a structural formula?

Answer 27

Condensed formulas omit bond lines. ## Footnote Condensed formulas simplify molecular representations by grouping atoms, while structural formulas show every bond and atom explicitly, providing a more detailed representation of the molecule's structure.

Question 28

What is the **empirical formula** for butane (C₄H₁₀)?

Answer 28

C₂H₅ ## Footnote The empirical formula for butane is derived by simplifying the ratio of carbon to hydrogen atoms. Dividing both 4 and 10 by their greatest common divisor (2), we get **C₂H₅**.

Question 29

What is the **symbol** for carbon?

Answer 29

C ## Footnote C is derived from **carbon**, which comes from the Latin "carbo" (meaning coal).

Question 30

What is the origin of the symbol **Fe** for iron?

Answer 30

From the Latin word **ferrum**. ## Footnote Latin names are sometimes used for element symbols.

Question 31

What do **subscripts** in chemical formulas indicate?

Answer 31

The **number of atoms** of an element in a molecule. ## Footnote Subscripts are written to the *lower right* of the element symbol, showing the number of atoms of that element in the formula. For H₂O, the subscript "2" means two hydrogen atoms.

Question 32

What does O₂ **represent**?

Answer 32

A **molecule** with two oxygen atoms. ## Footnote The subscript **2** indicates that the molecule consists of two oxygen atoms, forming dioxygen, the oxygen we breathe.

Question 33

What’s the difference between **coefficients** and **subscripts**?

Answer 33

* Coefficients indicate **molecule count**. * Subscripts indicate **atom count**. ## Footnote In the chemical formula **3CO**₂, The coefficient 3 indicates there are 3 molecules of carbon dioxide. The subscript 2 in CO₂ indicates there are 2 oxygen atoms in each molecule of carbon dioxide.

Question 34

What is a **superscript** in chemistry?

Answer 34

A **number** indicating charge or mass. ## Footnote Superscripts are often used to show the **charge** of ions (e.g., Na⁺), or mass numbers of isotopes (e.g., ¹⁴C)

Question 35

What does **Na⁺₁** represent?

Answer 35

A **sodium ion** with a +1 charge. ## Footnote The "+" sign indicates that the sodium atom has lost one electron, resulting in a positively charged ion.

Question 36

What is the **chemical formula** for methane?

Answer 36

CH₄ ## Footnote Methane consists of one carbon atom bonded to four hydrogen atoms, forming a tetrahedral structure.

Question 37

# True or False: The number 1 is **written** as a subscript in chemical formulas.

Answer 37

False ## Footnote In chemical formulas, the number **1** is implied but not written. For example, in H₂O, there is one oxygen atom, but no subscript is written next to the "O" (it’s implied to be 1).

Question 38

What does 2H₂O **represent**?

Answer 38

**Two** molecules of water. ## Footnote The coefficient **2** indicates two molecules of H₂O, or two water molecules, each consisting of two hydrogen atoms and one oxygen atom.

Question 39

Why is periodic table nomenclature **important**?

Answer 39

It **standardizes** element identification and naming. ## Footnote The nomenclature helps avoid confusion among elements.

Question 40

# Fill in the blank: The **octet rule** states that atoms ideally want to have \_\_\_\_\_\_\_\_ electrons in their outermost electron shell.

Answer 40

Eight ## Footnote The term **octet** comes from the Greek root "oct" meaning eight, referring to the stable configuration of eight electrons in the outermost shell of an atom.

Question 41

How do covalent bonds **differ** from ionic bonds?

Answer 41

Covalent bonds **share** electrons; ionic bonds **transfer** electrons. ## Footnote In covalent bonds, atoms share electrons to achieve a full outer shell, while ionic bonds form when one atom gives up electrons and another accepts them, creating oppositely charged ions.

Question 42

What is **electronegativity**?

Answer 42

The tendency of atoms to **attract** electrons. ## Footnote It is a measure of an atom’s ability to attract shared electrons in a bond. Nonmetals generally have higher electronegativity than metals.

Question 43

# True or False: Metals have **high** electronegativity.

Answer 43

False ## Footnote Metals tend to lose electrons easily and have low electronegativity, while nonmetals, which gain electrons, have higher electronegativity.

Question 44

What are the **four** main blocks of elements?

Answer 44

* s-block * p-block * d-block * f-block ## Footnote These blocks **categorize** elements based on their electron configuration, with s-block and p-block elements being more chemically reactive than d-block and f-block elements.

Question 45

How many **valence electrons** do elements in the s-block have?

Answer 45

One or two valence electrons. ## Footnote Column one has one valence electron, and column two has two valence electrons.

Question 46

# Fill in the blank: A **Lewis dot structure** is a diagram that shows bonds between atoms using \_\_\_\_\_\_ to represent valence electrons.

Answer 46

dots ## Footnote These diagrams help **visualize** how atoms share electrons to form bonds, aiding in understanding molecular structure and reactivity.

Question 47

What elements are typically **found** in the center of a Lewis structure?

Answer 47

The **least** electronegative element. ## Footnote The center atom in a Lewis structure is usually the one that can form the most bonds, and it’s often the least electronegative. For example, in CO₂, carbon is in the center because it's less electronegative than oxygen. Hydrogen, being highly electronegative, always goes on the outside if only two atoms are involved.

Question 48

How many **electrons** do noble gases have in their valence shell?

Answer 48

eight ## Footnote Noble gases are stable with a full outer shell, except helium, which has two electrons.

Question 49

What happens during **chemical bonding**?

Answer 49

**Atoms** transfer or share electrons. ## Footnote Atoms bond to achieve a more **stable** electron configuration, either by sharing or transferring electrons.

Question 50

In **ionic bonding**, what happens to the electrons?

Answer 50

One atom **transfers** electrons to the other. ## Footnote The atom that donates electrons becomes positively charged (cation), while the atom that gains electrons becomes negatively charged (anion).

Question 51

# Define: Covalent bonding

Answer 51

Atoms **share electrons** and form electron pairs.

Question 52

# True or False: The two **types** of covalent bonds are non-polar and polar.

Answer 52

True ## Footnote *Non-polar* covalent bonds occur when electrons are shared equally, while *polar* covalent bonds occur when electrons are shared unequally between atoms.

Question 53

Sodium chloride is an **example** of what type of bond?

Answer 53

Ionic bond ## Footnote Sodium chloride (NaCl) is an example of an ionic bond, where electrons are transferred from sodium (Na) to chlorine (Cl), resulting in oppositely charged ions that are held together by electrostatic forces.

Question 54

# True or False: Water is **not** an example of a covalent bond.

Answer 54

False ## Footnote Water (H₂O) is an **example** of a covalent bond, where electrons are shared between hydrogen and oxygen atoms.

Question 55

What are **hydrogen bonds**?

Answer 55

Attractive forces **between** hydrogen and electronegative atoms. ## Footnote Hydrogen bonds occur when hydrogen, bonded to an electronegative atom, interacts with another electronegative atom, like oxygen or nitrogen.

Question 56

# Fill in the blank: In an ionic bond, the more **electronegative** atom becomes a/an \_\_\_\_\_\_\_.

Answer 56

Anion ## Footnote The more electronegative atom gains electrons, becoming negatively charged (anion).

Question 57

# Fill in the blank: In an ionic bond, the atom that **donates** the electron is called a/an \_\_\_\_\_\_\_.

Answer 57

Cation ## Footnote The atom that donates an electron becomes positively charged and is known as the cation.

Question 58

What is the **effect** of higher charges on ionic bond strength?

Answer 58

The bond strength **increases**. ## Footnote Higher charges **lead** to a stronger electrostatic attraction between the ions.

Question 59

# True or False: Intermolecular forces **affect** physical properties.

Answer 59

True ## Footnote These [forces](https://study.com/academy/lesson/intermolecular-forces-in-chemistry-definition-types-examples.html) determine properties like melting/boiling points and solubility.

Question 60

What **force** exists between hydrogen and electronegative atoms like oxygen or nitrogen?

Answer 60

Hydrogen bonding ## Footnote Hydrogen bonds are a type of **intermolecular force** that occurs when a hydrogen atom covalently bonded to an electronegative atom (such as oxygen, nitrogen, or fluorine) is attracted to another electronegative atom.

Question 61

# Fill in the blank: **Dipole-dipole** interactions occur between \_\_\_\_\_\_\_ molecules.

Answer 61

polar ## Footnote Polar molecules have partial positive and negative charges that attract each other.

Question 62

# True or False: London dispersion forces are **stronger** than hydrogen bonding and dipole-dipole interactions.

Answer 62

False ## Footnote London dispersion forces are temporary and weaker than hydrogen bonding or dipole-dipole interactions, which involve more permanent dipoles or stronger attractions.

Question 63

What type of **force** is found in nonpolar substances?

Answer 63

London dispersion forces. ## Footnote Nonpolar substances have weak forces, leading to lower melting/boiling points.

Question 64

# Fill in the blank: A substance with **weak** intermolecular forces has \_\_\_\_\_\_\_ vapor pressure.

Answer 64

higher ## Footnote Weak forces allow more molecules to escape into the gas phase, increasing vapor pressure.

Question 65

What **happens** to boiling points as molecular surface area increases?

Answer 65

Boiling points **increase**. ## Footnote Larger surface areas allow molecules to interact more strongly, raising boiling points.

Question 66

What is the **primary** force in ionic compounds?

Answer 66

Electrostatic attraction ## Footnote The positive and negative ions in ionic compounds attract each other, creating *strong forces*.

Question 67

# Fill in the blank: **Stronger** intermolecular forces \_\_\_\_\_\_ vapor pressure.

Answer 67

lower ## Footnote Molecules with stronger intermolecular forces are less likely to escape into the gas phase, resulting in a lower vapor pressure.

Question 68

What is **solubility**?

Answer 68

The **maximum** amount of solute that dissolves in a solvent at a specific temperature. ## Footnote This depends on factors like temperature, pressure (for gases), and the nature of the solute and solvent.

Question 69

# True or False: "*Like dissolves like*" is a **principle** of solubility.

Answer 69

True ## Footnote Polar solvents tend to dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes due to similar intermolecular forces.