Unit 4

At standard pressure, CH4 boils at 112 K and H2O boils at 373 K. What accounts for the higher boiling point of H 2O at standard pressure? 1) covalent bonding 2) ionic bonding 3) hydrogen bonding 4) metallic bonding

3

Hydrogen bonding is a type of 1) strong covalent bond 2) weak ionic bond 3) strong intermolecular force 4) weak intermolecular force

3

Which kinds of bonds are found in a sample of liquid H2O? 1) covalent bonds, only 2) hydrogen bonds, only 3) both covalent and hydrogen bonds 4) both ionic and hydrogen bonds

3

Which statement explains why low temperature and high pressure are required to liquefy chlorine gas? Chlorine molecules have weak covalent bonds. 2) Chlorine molecules have strong covalent bonds. 3) Chlorine molecules have weak intermolecular forces of attraction. 4) Chlorine molecules have strong intermolecular forces of attraction.

3

Based on intermolecular forces, which of these substances would have the highest boiling point? 1) He 2) O2 3) CH4 4) NH3

4

Molecules in a sample of NH3(l ) are held closely together by intermolecular forces 1) existing between ions 2) existing between electrons 3) caused by different numbers of neutrons 4) caused by unequal charge distribution

4

Which statement explains why Br2 is a liquid at STP and I2 is a solid at STP? 1) Molecules of Br2 are polar, and molecules of I2 are nonpolar. 2) Molecules of I2 are polar, and molecules of Br2 are nonpolar. 3) Molecules of Br2 have stronger intermolecular forces than molecules of I2 . 4) Molecules of I2 have stronger intermolecular forces than molecules of Br2 .

4

A type of chemical bond that is consists of positive ions in a sea of electrons a(n) A. covalent bond. B. ionic bond. C. metallic bond D. hydrogen bond

C

Which molecule would have the largest dipole? (A) H2 (B) CH4 (C) HF (D) HCl (E) HBr

C

Which molecule would have the largest dipole? (A) N2 (B) O2 (C) NH3 (D) P4 (E) CH4

C

Which of the following is expected to have the highest normal boiling point? (A) C2H6 (B) C3H8 (C) C5H12 (D) C4H10 (E) CH4

C

Henry's Law

C = kP C = concentration of a dissolved gas k = Henry's Law constant P = partial pressure of the gas

A pure substance melts at 88°C and does not conduct electricity in either the solid state or the liquid state. It does not dissolve very well in water but it does dissolve in nonpolar solvents is most likely to be A. a metal B. a network solid C. an ionic compound D. a covalent compound

D

A weak attraction between a hydrogen atom in one molecule and an oxygen in another is called a(n) A. ionic bond. B. covalent bond C. metallic bond D. hydrogen bond

D

Which molecule would have the largest dispersion molecules forces between other identical? (A) H2Se (B) H2O (C) H2S (D) H2Te (E) H2

D

Which molecule would have the strongest tendency to form hydrogen bonds with other identical molecules? (A) H2 (B) CH4 (C) C2H6 (D) HF (E) HCl

D

Which of the following best describes all the intermolecular forces exhibited by a pure sample of CH3NH2? (A) dispersion only (B) dipole-dipole and hydrogen bonding (C) dispersion and hydrogen bonding (D) dispersion, dipole-dipole, and hydrogen bonding (E) dispersion and dipole-dipole

D

Which pure substance would have the largest molar heat of vaporization? (A) Ar (B) H2 (C) N2 (D) H2O (E) CH4

D

Which pure substance would have the smallest molar heat of vaporization? (A) C4H10 (B) C5H12 (C) C3H8 (D) CH4 (E) C2H6

D

Second weakest IMF

Dipole-dipole

Which molecule would have the largest dispersion forces between other identical molecules? (A) CCl4 (B) CBr4 (C) CF4 (D) CH4 (E) CI4

E

Which molecule would have the largest dispersion molecules forces between other identical? (A) CH4 (B) C3H8 (C) C2H6 (D) C2H4 (E) C4H10

E

Which molecule would have the strongest tendency to form hydrogen bonds with other identical molecules? (A) C2H4 (B) SiH4 (C) CO2 (D) F2 (E) C2H5OH

E

Which molecule would have the strongest tendency to form hydrogen bonds with other identical molecules? (A) C3H8 (B) N2 (C) H2S (D) Cl2 (E) H2O

E

Which of the following best describes all the intermolecular forces exhibited by a pure sample of CH3Cl? (A) dispersion only (B) dipole-dipole and hydrogen bonding (C) dispersion and hydrogen bonding (D) dispersion, dipole-dipole, and hydrogen bonding (E) dispersion and dipole-dipole

E

Which of the following best describes all the intermolecular forces exhibited by a pure sample of PH3? (A) dispersion only (B) dipole-dipole and hydrogen bonding (C) dispersion and hydrogen bonding (D) dispersion, dipole-dipole, and hydrogen bonding (E) dispersion and dipole-dipole

E

Which of the following is expected to have the lowest normal boiling point? (A) C2H6 (B) C3H8 (C) C5H12 (D) C4H10 (E) CH4

E

Properties of ionic bonds

Form crystals High melting and boiling points Conduct electricity when dissolved in water Good Insulators Hard and Brittle

Strongest IMF (excluding ion-ion)

Ion-dipole

Using your knowledge of chemistry and the information in Reference Table H, which statement concerning propanone and water at 50°C is true? 1) Propanone has a higher vapor pressure and stronger intermolecular forces than water. 2) Propanone has a higher vapor pressure and weaker intermolecular forces than water. 3) Propanone has a lower vapor pressure and stronger intermolecular forces than water. 4) Propanone has a lower vapor pressure and weaker intermolecular forces than water.

2

What happens when NaCl(s) is dissolved in water? 1) Cl - ions are attracted to the oxygen atoms of water molecules. 2) Na+ ions are attracted to the oxygen atoms of water molecules. 3) Cl - ions are repelled by the hydrogen atoms of water molecules. 4) Na+ ions are repelled by the oxygen atoms of water molecules.

2

Which represents a sample containing molecule-ion attractions? 1) CH4(g) 2) NaCl(aq) 3) H2O(g) 4) Hg(l)

2

Heat of vaporization

the energy a substance must absorb in order to change from a liquid to a gas

Heat of Sublimation

the energy a substance must absorb in order to change from a solid to a gas

Heat of fusion

the energy a substance must absorb in order to change from a solid to a liquid

large positive value for the heat of solution means

the substance will not dissolve

For a solid solute dissolving in water, as temp goes up, solubility goes

up

Enthalpy of solution

ΔHsolution = ΔHsolute + ΔHsolvent + ΔHmix

Boiling point elevation

ΔTb = m i Kb

freezing point depression

ΔTf = m i Kf

Raoult's Law

Psolution = Xsolvent * Posolvent Psolution = vapor pressure of the solution Xsolvent = mole fraction of SOLVENT Posolvent = vapor pressure of the pure solvent

As the distance between two bromine molecules increases, the magnitude of the atractive forces between them 1) decreases 2) increases 3) remains the same

1

At 50.°C and standard pressure, intermolecular forces of attraction are strongest in a sample of 1) ethanoic acid 2) ethanol 3) propanone 4) water

1

In an aqueous solution of Ca(NO3)2, which kind of attraction exists between the solute and the solvent? 1) molecule-ion attraction 2) molecule-molecule attraction 3) hydrogen bond 4) van der Waals force

1

In aqueous solution, a chloride ion is attracted to which end of the water molecule? 1) the hydrogen end, which is the positive pole 2) the hydrogen end, which is the negative pole 3) the oxygen end, which is the positive pole 4) the oxygen end, which is the negative pole

1

In which liquid is hydrogen bonding strongest? 1) HF(l) 2) H2(l) 3) CH4(l) 4) NH3(l)

1

The strongest attractions exist between molecules of...? (Hint: The mass of these elements is presented on the Periodic Table) 1) I2 2) Br2 3) Cl2 4) F2

1

Which of these substances has the strongest intermolecular forces? 1) H2O 2) H2S 3) H2Se 4) H2Te

1

At STP, fluorine is a gas and bromine is a liquid because, compared to fluorine, bromine has 1) stronger covalent bonds 2) stronger intermolecular forces 3) weaker covalent bonds 4) weaker intermolecular forces

2

Intermolecular attractions strength affect a substances 1) nuclear charge 2) melting point temperature 3) spectral lines 4) chemical properties

2

A pure substance does not conduct electricity in the solid state but it does dissolve in water and the resulting solution conducts electricity. The substance has a fairly high melting point. The substance is most likely to be A. an ionic compound B. a covalent compound C. a metal D. a network solid

A

Which molecule would have the largest dipole? (A) NH3 (B) CO2 (C) C2H6 (D) AsH3 (E) BrCl

A

Which molecule would have the largest dispersion forces between other identical molecules? (A) BiH3 (B) AsH3 (C) NH3 (D) PH3 (E) SbH3

A

Which molecule would have the strongest tendency to form hydrogen bonds with other identical molecules? (A) NH3 (B) CH4 (C) H2 (D) HBr (E) C2H6

A

Which of the following best describes all the intermolecular forces exhibited by a pure sample of CS2? (A) dispersion only (B) dipole-dipole and hydrogen bonding (C) dispersion and hydrogen bonding (D) dispersion, dipole-dipole, and hydrogen bonding (E) dispersion and dipole-dipole

A

Which of the following is expected to have the highest normal boiling point? (A) HF (B) HCl (C) HBr (D) HI (E) HAt

A

A negatively charged ion attracts a(n) A. anion B. cation C. neutral atom D. proton

B

A type of chemical bond that is formed from the attraction of an atom that has lost an electron for an atom that has gained an electron is called a(n) A. covalent bond. B. ionic bond. C. metallic bond D. hydrogen bond

B

What is the name of the intermolecular force caused by an instantaneous dipole in the particles? (A) ionic attraction (B) dispersion force (C) covalent bond (D) dipole-dipole force (E) hydrogen bond

B

When covalent bonds are formed between atoms having different electronegativities, the electrons tend to spend more time at the atom with the greater electronegativity. Such chemical bonds are called A. electrovalent bonds B. polar covalent bonds C. coordinate covalent bonds D. none of the above

B

Which molecule would have the largest dipole? (A) CH4 (B) H2O (C) CO2 (D) SO3 (E) F2

B

Which molecule would have the largest dipole? (A) CO2 (B) ClF (C) Br2 (D) I2 (E) H2

B

Which molecule would have the largest dispersion forces between other identical molecules? (A) F2 (B) I2 (C) Br2 (D) Cl2 (E) H2

B

Which molecule would have the strongest tendency to form hydrogen bonds with other identical molecules? (A) C2H4 (B) CH3OH (C) CO2 (D) F2 (E) SiH4

B

Which of the following is a polar molecule? (A) CO2 (B) NH3 (C) CH4 (D) SiF4 (E) None of the above

B

Which of the following is expected to have the highest normal boiling point? (A) H2 (B) Br2 (C) O2 (D) N2 (E) F2

B

Second strongest IMF

Hydrogen bonding

Weakest IMF

London dispersion

order of IMFs from weakest to strongest

London, dipole-dipole, hydrogen bonding, ionic, covalent network (metallic is somewhere in between most of these)

sea of mobile electrons

Loosely held outer electrons are shared by all metal atoms

Covalent bond properties

Low boiling and melting points Poor conductors Brittle

metallic bond

The attraction of the stationary metal cations to the surrounding mobile electrons

Mole Fraction

XA = moles A / moles A+B

Hydrogen bonding

between molecules containing an H-F, H-O, or H-N bond (E.T. FON home)

London Forces

between nonpolar molecules

Dipole-dipole forces

between polar molecules

Ionic compounds -

crystal lattice formed from both cations and anions

Metals -

crystal lattice formed from cations

As IMFs increase, vapor pressure

decreases

For a gaseous solute dissolving in water, as temp goes up, solubility goes

down

ΔHsolute and ΔHsolvent are

endothermic (+)

As IMFs increase, boiling point

increases

Crystalline solids

lattice structure orderly arrangement of particles metals, ceramics, diamond break on planes

Mass Percent

mass of solute / mass of solution * 100%

Molality

moles solute / kg solution

Molarity

moles solute / liters of solution

A few covalent substances =

network (diamond, SiC, SiO2)

osmotic pressure formula

pi= iMRT R = 0.08206

Amorphous solids

random arrangement of particles glass, coal Uneven IMFs mean that they have gradual melting points Break unevenly