Test 02

Describe how a covalent bond holds two atoms together.

A pair of electrons is attracted to both nuclei of the two atoms bonded together.

Some binary compounds are ionic, others are covalent. The type of bond favored partially depends on the position of the elements in the periodic table. Label each of these claims as True or False; if False, specify the nature of the error.

a. Covalently bonded binary molecular compounds are typically composed of nonmetals. - True b. Binary ionic compounds are composed of metals and nonmetals, typically from opposite sides of the periodic table. - True

Refer to the text for examples of names and formulas for polyatomic ions and acids.

a. Derive a generalization for determining whether an acid name will end in the suffix -ic or -ous. - a. In general, if the anion name ends in -ate, the corresponding acid name will end in a suffix of -ic. In general, if the anion name ends in -ite, the corresponding acid name will end in a suffix of -ous. b. Derive a generalization for determining whether an acid name will begin with the prefix hydro- or not. - b. In general, anion name ends in -ide, the corresponding acid name will end in a suffix of -ic and begin with a prefix of hydro-. The prefix hydro- is never used for anions ending in -ate or -ite.

A compound is found to contain 43.2% copper, 24.1% chlorine, and 32.7% oxygen by mass.

a. Determine its empirical formula. - a. CuClO3 b. What is the correct Stock system name of the compound in part a? - b. copper(I) chlorate

Gas X is found to be 24.0% carbon and 76.0% fluorine by mass.

a. Determine the empirical formula of gas X. - a. CF2 b. Given that the molar mass of gas X is 200.04 g/mol, determine its molecular formula. - b. C4F8

What property of the two atoms in a covalent bond determines whether or not the bond will be polar?

electronegativity

What two factors determine whether or not a molecule is polar?

electronegativity difference and molecular geometry or unshared electron pairs

Number 3

fluorine - a. Use electronegativity values to determine the one element that always has a negative oxidation number when it appears in any binary compound. O;F2 - b. What is the oxidation number and formula for the element described in part a when it exists as a pure element?

The notation for sodium chloride, NaCl, stands for one

formula unit

Atoms with a strong attraction for electrons they share with another atom exhibit

high electronegativity

Tin has possible oxidation numbers of +2 and +4 and forms two known oxides. One of them has the formula SnO2.

tin(IV) oxide - a. Give the Stock system name for SnO2. SnO - b. Give the formula for the other oxide of tin.

When a metal is drawn into a wire, the metallic bonds

do not break

Assign the oxidation number to the specified element in each of the following examples:

+4 - a. S in H2SO3 +6 - b. S in MgSO4 -2 - c. S in K2S +1 - d. Cu in Cu2S +6 - e. Cr in Na2CrO4 +5 - f. N in HNO3 +4 - g. C in (HCO3)− -3 - h. N in (NH4)+

A bond's character is more than 50% ionic if the electronegativity difference between the two atoms is greater than

1.7

How many atoms are present in each of these formula units?

11 atoms - a. Ca(HCO3)2 45 stoms - b. C12H22O11 10 atoms - c. Fe(ClO2)3 9 atoma - d. Fe(ClO3)2

What orbitals combine together to form sp3 hybrid orbitals around a carbon atom?

the s orbital and all three p orbitals from the second energy level

Arrange the following types of attractions in order of increasing strength, with 1 being the weakest and 4 the strongest.

3 - Hydrogen bonding 4 - ionic 2 - dipole-dipole 1 - London dispersion

The explosive TNT has the molecular formula C7H5(NO2)3.

4 elements - a. How many elements make up this compound? 6 oxygen atoms - b. How many oxygen atoms are present in one molecule of C7H5(NO2)3? 21 atoms - c. How many atoms in total are present in one molecule of C7H5(NO2)3? 4.2NO6^24 atoms - d. How many atoms are present in a sample of 2.0 × 1023 molecules of C7H5(NO2)3?

Use the concept of potential energy to describe how a covalent bond forms between two atoms.

As the atoms involved in the formation of a covalent bond approach each other, the electron-proton attraction is stronger than the electron-electron and proton-proton repulsions. The atoms are drawn to each other and their potential energy decreases. Eventually, a distance is reached at which the repulsions between the like charges equals the attraction of the opposite charges. At this point, potential energy is at a minimum and a stable molecule forms.

Arrange the bonds listed in order of increasing bond length, from shortest bond to longest. b. Bond - Bond energy C—C - 346 C(3 bars)C - 835 C == C - 612

C(3 bars)C, C==C, C—C

Number 2

C4H8 - A certain hydrocarbon has an empirical formula of CH2 and a molar mass of 56.12 g/mol. What is its molecular formula?

Write empirical formulas to match the following molecular formulas:

CH3O2 = C2H6O4 N2O5 = N2O5 Hg2Cl2 = HgCl C6H12 = CH2

The oxidation numbers assigned to the atoms in some organic compounds have unexpected values. Assign oxidation numbers to each atom in the following compounds: (Note: Some oxidation numbers may not be whole numbers.)

CO2 (carbon dioxide) a. Carbon is +4 and each oxygen is −2. CH4 (methane) b. Carbon is −4 and each hydrogen is +1. C6H12O6 (glucose) c. Each carbon is 0, each hydrogen is +1, and each oxygen is −2. C3H8 (propane gas) d. Each carbon is −8/3 and each hydrogen is +1.

Name two elements that form compounds that can be exceptions to the octet rule.

Choose from hydrogen, boron, beryllium, phosphorus, sulfur, and xenon.

Fill in the blanks in the table below.

Compound name - Formula Aluminum sulfide - Al2S3 Cesium carbonate - Cs2CO3 Lead (II) chloride - PbCl2 Ammonium phosphate - (NH4)3PO4 Hydroiodic acid - HI

Bond energy is related to bond length. Use the data in the tables below to arrange the bonds listed in order of increasing bond length, from shortest bond to longest. a. Bond - Bond energy H—F - 569 H—I - 299 H—Cl - 432 H—Br - 366

H—F, H—Cl, H—Br, H—I

Identify the major assumption of the VSEPR theory, which is used to predict the shape of atoms.

Pairs of valence electrons repel one another.

The lattice energy of compound A is greater in magnitude than that of compound B. What can be concluded from this fact?

It will be more difficult to break the bonds in compound A than those in compound B.

Arrange the ionic bonds in the table below in order of increasing strength from weakest to strongest. Ionic bond - Lattice energy NaCl - (-787) CaO - (-3384) KCl - (-715) MgO - (-3760) LiCl - (-861)

KCl, NaCl, LiCl, CaO, MgO

Use the concept of electron configurations to explain why the number of valence electrons in metals tends to be less than the number in most nonmetals.

Most metals have their outer electrons in s orbitals, while nonmetals have their outer electrons in p orbitals.

Consider the covalent compound dinitrogen trioxide when answering the following:

N2O3 - a. What is the formula for dinitrogen trioxide? +3 - b. What is the oxidation number assigned to each nitrogen atom in this compound? Explain your answer - The three oxygen atoms have oxidation states of −6 total, and because the algebraic sum of the oxidation states in a neutral compound must be zero, the two nitrogen atoms must have oxidation states of +6 total, therefore +3 nitrogen(III) oxide - c. Give the Stock name for dinitrogen trioxide.

Number 5

N2O5 - a. What is the formula for the compound dinitrogen pentoxide? iron (ii) oxide - b. What is the Stock system name for the compound FeO? H2SO3 - c. What is the formula for sulfurous acid? phosphoric acid - d. What is the name for the acid H3PO4?

Explain why resonance structures are used instead of Lewis structures to correctly model certain molecules.

Resonance structures show that one Lewis structure cannot correctly represent the location of electrons in a bond. Resonance structures show delocalized electrons, while Lewis structures depict electrons in a definite location.

Assign oxidation numbers to each element in the compounds found in the following situations:

Rust, Fe2O3, forms on an old nail. a. Each iron is +3 and each oxygen is −2. Nitrogen dioxide, NO2, pollutes the air as a component of smog. b. Nitrogen is +4 and each oxygen is −2. Chromium dioxide, CrO2, is used to make recording tapes. c. Chromium is +4 and each oxygen is −2.

Number 2

SCl2 - a. What is the formula for the compound sulfur (II) chloride? nitrogen(IV) oxide - b. What is the Stock system name for NO2?

What is the relationship between the enthalpy of vaporization of a metal and the strength of the bonds that hold the metal together?

The amount of energy required to vaporize a metal is a measure of the strength of the bonds that hold the metal together. The greater a metal's enthalpy of vaporization, the stronger the metallic bond.

What types of bonds are present in an ionic compound that contains a polyatomic ion?

The atoms in a polyatomic ion are held together with covalent bonds, but polyatomic ions combine with ions of opposite charge to form ionic compounds.

How can electronegativity be used to distinguish between an ionic bond and a covalent bond?

The difference between the electronegativity of the two atoms in a bond will determine whether the bond is ionic or covalent. If the difference in electronegativity is greater than 1.7, the bond is considered ionic.

Describe the electron distribution in a polar-covalent bond and its effect on the partial charges of the compound.

The electron density is greater around the more electronegative atom, giving that part of the compound a partial negative charge. The other part of the compound has an equal partial positive charge.

In water, two hydrogen atoms are bonded to one oxygen atom. Why isn't water a linear molecule?

The electron pairs that are not involved in bonding also take up space, creating a tetrahedron of electron pairs and making the water molecule angular or bent.

Describe the force that holds two ions together in an ionic bond.

The force of attraction between unlike charges holds a negative ion and a positive ion together in an ionic bond.

How does the behavior of electrons in metals contribute to the metal's ability to conduct electricity and heat?

The mobility of electrons in a network of metal atoms contributes to the metal's ability to conduct electricity and heat.

How are dipole-dipole attractions, London dispersion forces, and hydrogen bonding similar?

They are all forces of attraction between molecules. In all cases there is an attraction between the slightly negatively-charged portion of one molecule and the slightly positively charged portion of another molecule.

A certain ionic compound is found to contain 0.012 mol of sodium, 0.012 mol of sulfur, and 0.018 mol of oxygen.

What is its empirical formula? - a. Na2S2O3 Is this compound a sulfate, sulfite, or neither? - b. neither

According to VSEPR theory, which molecule gas a bent shape?

`

A covalent bond consists of

a shared electron pair

Water of hydration was discussed in Sample Problem K in Section 4 of the text. Strong heating will drive off the water as a vapor in hydrated copper (II) sulfate. Use the data table below to answer the following: Mass of the empty crucible - 4.00 g Mass of the crucible plus hydrate sample - 4.50g Mass of the system after heating - 4.32 g Mass of the system after a second heating - 4.32g

a. Determine the mass percentage of water in the original sample. - a. 36% b. The compound has the formula CuSO4 • xH2O - b. 5 c. What might be the purpose of the second heating? - c. The second heating is to ensure that all the water in the sample has been driven off. If the mass is less after the second heating, water was still present after the first heating.

Write the formula for the n example of each of the following compounds:

a. H2 - non polar covalent compound b. HCl - polar covalent compound c. NaCl - ionic compound

Scientists think that two separate reactions contribute to the depletion of the ozone, O3, layer. The first reaction involves oxides of nitrogen. The second involves free chlorine atoms. The equations that represent the reactions follow. When a compound is not stated as a formula, write the correct formula in the blank beside its name.

a. NO (nitrogen monoxide) + O3 → NO2 (nitrogen dioxide) + O2 b. Cl + O3 → ClO (chlorine monoxide) + O2

As light strikes the surface of a metal, the electrons in the electron sea

absorb and re-emit the light.

Changing a subscript in a correctly written chemical formula

changes the formula so that it no longer represents the compound it previously represented.

The fact that metals are malleable and ionic crystals are brittle is best explained in terms of their

chemical bonds.

In general, the strength of the metallic bond _________ moving from left to right on any row of the periodic table.

increases

A chemical bond that results from the electrostatic attraction between positive and negative ions is called a(n) _______________.

ionic bond

If a bond's character is more than 50% ionic, then the bond is called a(n) ________________

ionic bond

The greater the electronegativity difference between two atoms bonded together, the greater the bond's percentage of

ionic character

What type of energy best represents the strength of an ionic bond?

lattice energy

the shape of molecules that contain only two atoms is...

linear

Compared with the neutral atoms involved in the formation of an ionic compound, the crystal lattice that results is

lower in potential energy

Mobile electrons in the metallic bond are responsible for

luster, thermal conductivity, electrical conductivity

In a crystal of an ionic compound, each cation is surrounded by a number of

negative ions

If two covalently bonded atoms are identical, the bond is identified as

nonpolar covalent

A chemical bond between atoms results from the attraction between the valence electrons and of _____ different atoms.

nuclei

A covalent bond in which there is an unequal attraction for the shared electrons is

polar

Bonds that possess between 5% and 50% ionic character are considered to be

polar covalent

If electrons involved in bonding spend most of the time closer to one atom rather than the other, the bond is _______________________

polar covalent

VSEPR theory

predicts the shape of some molecules and assumes that pairs of valence electrons surrounding an atom repel each other.

In metals, the valence electrons are considered to be

shared by all surrounding atoms.

In a Stock system name such as iron(III) sulfate, the Roman numeral tells us

the charge on each Fe ion.

The electrons involved in the formation of a chemical bond are called ______

valence electrons

The forces of attraction between molecules in a molecular compound are generally

weaker than the attractive forces among formula units in ionic bonding