American Chemical Society General Chemistry Bonding and States

Question 1

Sodium and chlorine combine to form a compound. Which description of the bond is correct?

Accepted Answer

Ionic, because sodium is a metal and chlorine is a nonmetal

Question 2

Carbon and oxygen bond in carbon dioxide. Which description of that bond is correct?

Accepted Answer

Covalent, because carbon and oxygen are both nonmetals

Question 3

Magnesium and oxygen form a compound. Which description of the bond is correct?

Accepted Answer

Ionic, because magnesium is a metal and oxygen is a nonmetal

Question 4

Hydrogen and chlorine bond in hydrogen chloride. Which description of the bond is correct?

Accepted Answer

Covalent, because hydrogen and chlorine are both nonmetals

Question 5

Potassium and bromine combine. Which description of the bond is correct?

Accepted Answer

Ionic, because potassium is a metal and bromine is a nonmetal

Question 6

Carbon and hydrogen bond in methane. Which description of the bond is correct?

Accepted Answer

Covalent, because carbon and hydrogen are both nonmetals

Question 7

Calcium and fluorine form a compound. Which description of the bond is correct?

Accepted Answer

Ionic, because calcium is a metal and fluorine is a nonmetal

Question 8

Sulfur and oxygen bond in sulfur dioxide. Which description of the bond is correct?

Accepted Answer

Covalent, because sulfur and oxygen are both nonmetals

Question 9

Barium and oxygen form a compound. Which description of the bond is correct?

Accepted Answer

Ionic, because barium is a metal and oxygen is a nonmetal

Question 10

In the Lewis structure of ammonia, NH3, how many bonding electron pairs and lone pairs are on nitrogen?

Accepted Answer

Three bonding pairs and one lone pair

Question 11

In the Lewis structure of water, how many bonding electron pairs and lone pairs are on oxygen?

Accepted Answer

Two bonding pairs and two lone pairs

Question 12

In the Lewis structure of methane, how many bonding electron pairs and lone pairs are on carbon?

Accepted Answer

Four bonding pairs and no lone pairs

Question 13

In the Lewis structure of boron trifluoride, BF3, how many bonding electron pairs and lone pairs are on boron?

Accepted Answer

Three bonding pairs and no lone pairs

Question 14

In the Lewis structure of phosphorus trichloride, PCl3, how many bonding electron pairs and lone pairs are on phosphorus?

Accepted Answer

Three bonding pairs and one lone pair

Question 15

Carbon dioxide is drawn as O=C=O. Counting every shared electron pair, how many bonding pairs and lone pairs are on carbon?

Accepted Answer

Four bonding pairs and no lone pairs

Question 16

In the Lewis structure of hydrogen sulfide, H2S, how many bonding electron pairs and lone pairs are on sulfur?

Accepted Answer

Two bonding pairs and two lone pairs

Question 17

In the Lewis structure of carbon tetrachloride, how many bonding electron pairs and lone pairs are on carbon?

Accepted Answer

Four bonding pairs and no lone pairs

Question 18

In the Lewis structure of nitrogen trifluoride, NF3, how many bonding electron pairs and lone pairs are on nitrogen?

Accepted Answer

Three bonding pairs and one lone pair

Question 19

Carbon dioxide has two electron domains on carbon and no lone pairs. What is the molecular shape?

Accepted Answer

Linear, because two electron domains stay opposite each other

Question 20

Boron trifluoride has three bonding domains on boron and no lone pairs. What is the molecular shape?

Accepted Answer

Trigonal planar, because three domains spread 120 degrees apart

Question 21

Water has two bonding domains and two lone pairs on oxygen. What is the molecular shape?

Accepted Answer

Bent, because the two lone pairs push the two bonds together

Question 22

Methane has four bonding domains on carbon and no lone pairs. What is the molecular shape?

Accepted Answer

Tetrahedral, because four domains point to the corners of a tetrahedron

Question 23

Ammonia has three bonding domains and one lone pair on nitrogen. What is the molecular shape?

Accepted Answer

Trigonal pyramidal, because the lone pair holds one corner of the tetrahedron

Question 24

Hydrogen cyanide, HCN, has two electron domains on carbon and no lone pairs. What is the molecular shape?

Accepted Answer

Linear, because two electron domains point 180 degrees apart

Question 25

Formaldehyde, CH2O, has three bonding domains on carbon and no lone pairs. What is the molecular shape?

Accepted Answer

Trigonal planar, because three bonding domains lie in one plane

Question 26

Carbon tetrachloride has four bonding domains on carbon and no lone pairs. What is the molecular shape?

Accepted Answer

Tetrahedral, because four bonding domains point toward tetrahedron corners

Question 27

Hydrogen sulfide has two bonding domains and two lone pairs on sulfur. What is the molecular shape?

Accepted Answer

Bent, because two lone pairs push the bonding pairs closer together

Question 28

Carbon dioxide is linear, and each carbon-oxygen bond is polar. Is the molecule polar?

Accepted Answer

No, because the two equal bond dipoles point opposite ways and cancel

Question 29

Water is bent, and each O-H bond is polar. Is the molecule polar?

Accepted Answer

Yes, because the bent shape keeps the bond dipoles from canceling

Question 30

Carbon tetrachloride is tetrahedral, and each C-Cl bond is polar. Is the molecule polar?

Accepted Answer

No, because the four equal bond dipoles cancel in a tetrahedron

Question 31

Ammonia is trigonal pyramidal, and each N-H bond is polar. Is the molecule polar?

Accepted Answer

Yes, because the pyramidal shape leaves a net dipole

Question 32

Boron trifluoride is trigonal planar, and each B-F bond is polar. Is the molecule polar?

Accepted Answer

No, because the three equal dipoles cancel 120 degrees apart

Question 33

Hydrogen cyanide is linear, with polar bonds along H-C≡N. Is the molecule polar?

Accepted Answer

Yes, because the two ends differ and the dipoles do not cancel

Question 34

Silicon tetrafluoride is tetrahedral, and each Si-F bond is polar. Is the molecule polar?

Accepted Answer

No, because four equal dipoles cancel in tetrahedral symmetry

Question 35

Sulfur dioxide is bent, and each sulfur-oxygen bond is polar. Is the molecule polar?

Accepted Answer

Yes, because the bent shape leaves a net dipole

Question 36

Chloromethane, CH3Cl, is tetrahedral, and the C-Cl bond is polar. Is the molecule polar?

Accepted Answer

Yes, because replacing one hydrogen removes the symmetry and the dipoles do not cancel

Question 37

Carbon in CO2 has two electron domains and no lone pairs. What is the hybridization of that carbon?

Accepted Answer

sp, because two electron domains mix one s and one p orbital

Question 38

Boron in BF3 has three bonding domains and no lone pairs. What is the hybridization of boron?

Accepted Answer

sp2, because three electron domains mix one s and two p orbitals

Question 39

Carbon in methane has four bonding domains and no lone pairs. What is the hybridization of carbon?

Accepted Answer

sp3, because four electron domains mix one s and three p orbitals

Question 40

Nitrogen in ammonia has three bonding domains and one lone pair. What is the hybridization of nitrogen?

Accepted Answer

sp3, because the lone pair counts as a fourth electron domain

Question 41

Oxygen in water has two bonding domains and two lone pairs. What is the hybridization of oxygen?

Accepted Answer

sp3, because four domains, counting both lone pairs, need four hybrids

Question 42

Carbon in HCN has two electron domains, one single bond and one triple bond. What is the hybridization of that carbon?

Accepted Answer

sp, because two electron domains mix one s and one p orbital

Question 43

Carbon in formaldehyde, CH2O, has three bonding domains and no lone pairs. What is the hybridization of carbon?

Accepted Answer

sp2, because three electron domains mix one s and two p orbitals

Question 44

Each carbon in ethene, C2H4, has three bonding domains and no lone pairs. What is the hybridization of each carbon?

Accepted Answer

sp2, because three electron domains use one s and two p orbitals

Question 45

Beryllium in BeCl2 has two bonding domains and no lone pairs. What is the hybridization of beryllium?

Accepted Answer

sp, because two electron domains mix one s and one p orbital

Question 46

Water and hydrogen sulfide have similar bent shapes. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Water, because O-H groups hydrogen-bond and S-H groups do not

Question 47

Ammonia and phosphine, PH3, are both polar hydrides. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Ammonia, because N-H hydrogen bonding is stronger than the forces in phosphine

Question 48

Compare hydrogen fluoride with hydrogen chloride. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Hydrogen fluoride, because H-F hydrogen bonding beats the dipole-dipole forces in HCl

Question 49

Ethanol, CH3CH2OH, and dimethyl ether, CH3OCH3, have the same molecular formula. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Ethanol, because its O-H group hydrogen-bonds and the ether has no such hydrogen

Question 50

Neon and xenon are monatomic and nonpolar. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Xenon, because its larger electron cloud is more polarizable

Question 51

Compare chloromethane, CH3Cl, with methane. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Chloromethane, because it is polar and adds dipole-dipole forces to London forces

Question 52

Propane, C3H8, and octane, C8H18, are both nonpolar. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Octane, because its larger electron cloud gives stronger London forces

Question 53

Water and ammonia can both hydrogen-bond. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Water, because oxygen forms stronger hydrogen bonds and water has more lone pairs to accept them

Question 54

Fluorine, F2, and iodine, I2, are both nonpolar diatomic elements. Which has the stronger intermolecular force and the higher boiling point?

Accepted Answer

Iodine, because its larger electron cloud gives stronger London forces

Question 55

At 20 degrees Celsius, which liquid has the higher vapor pressure, water or diethyl ether, CH3CH2OCH2CH3?

Accepted Answer

Diethyl ether, because it cannot hydrogen-bond with itself and is held more weakly

Question 56

Which liquid boils at the lower temperature when the external pressure is 1 atm, ethanol or dimethyl ether?

Accepted Answer

Dimethyl ether, because weaker forces let its vapor pressure reach 1 atm at a lower temperature

Question 57

Which substance reaches a vapor pressure of 1 atm at the lower temperature, HF or HCl?

Accepted Answer

HCl, because dipole-dipole forces are weaker than the hydrogen bonding in HF

Question 58

Which substance boils at the lower temperature at 1 atm, ammonia or phosphine, PH3?

Accepted Answer

Phosphine, because it lacks hydrogen bonding, so its vapor pressure reaches 1 atm sooner

Question 59

At 20 degrees Celsius, which liquid has the higher vapor pressure, pentane, C5H12, or octane, C8H18?

Accepted Answer

Pentane, because its smaller electron cloud gives weaker London forces

Question 60

Which liquid boils at the lower temperature at 1 atm, water or acetone, CH3COCH3?

Accepted Answer

Acetone, because dipole-dipole forces are weaker than water's hydrogen bonds, so its vapor pressure reaches 1 atm sooner

Question 61

At 20 degrees Celsius, which liquid has the higher vapor pressure, methanol, CH3OH, or water?

Accepted Answer

Methanol, because its hydrogen-bond network is weaker than water's

Question 62

Which substance boils at the lower temperature at 1 atm, methane or chloromethane, CH3Cl?

Accepted Answer

Methane, because only London forces hold it, so its vapor pressure reaches 1 atm sooner

Question 63

At 20 degrees Celsius, which liquid has the higher vapor pressure, hexane, C6H14, or 1-hexanol, C6H13OH?

Accepted Answer

Hexane, because it has only London forces while 1-hexanol can hydrogen-bond

Question 64

Ice melts to liquid water at 0 degrees Celsius. Is this phase change endothermic?

Accepted Answer

Yes, melting absorbs heat to overcome attractions in the solid