Chapter 2: water

Question 1

Water has what type of geometry?

Answer 1

Bent

Question 2

How does the electrostatic attractions of water orientate themselves?

Answer 2

the O-H bond on one water molecule points towards a lone pair electron cloud on the oxygen of the other water molecule.

Question 3

Electrostatic attractions cause what?

Answer 3

Hydrogen bonding

Question 4

In genral how is a hydrogen bond repesented?

Answer 4

D-H….A where D-H is a weakly acidic donor such as N-H or O-H and A is a lone pair bearing and thus a weakly basic acceptor such as N or O

Question 5

Hydrogen bonds are structurally characterized by an H…A distance of what?

Answer 5

atleast 0.5 A shorter than the calculated van der waals distance

Question 6

What is Van der waals distance?

Answer 6

distance of closest approach between two non bonded atoms.

Question 7

How does the energy of a hydrogen bond compare to the energy of a covalent bond energy?

Answer 7

Hydrogen bond energy is small

Question 8

The central H2O molecule is what? and the others are what?

Answer 8

The central is the donor and the others are the acceptor.

Question 9

Water does what upon freezing?

Answer 9

expands

Question 10

Is frozen water more dense of less dense than liquid water?

Answer 10

Frozen water is less dense

Question 11

Liquid water is only ____% hydrogen bonded than ice at 0 degrees C

Answer 11

15%

Question 12

What does solubility depend on what?

Answer 12

ability of a solvent to interact with a solute more strongly than solute particles interact with eachother

Question 13

water is an excellent solvent for what type of molecules?

Answer 13

Polar

Question 14

Ions such as salts interact how?

Answer 14

According to columb’s law.

Question 15

How do the dielectrical constants of water differ from that of nonpolar substances:

Answer 15

The dielectrical constant of water is among the highest while the dielectrical constant of nonpolar substances are relatively small.

Question 16

How is the forces of ions in water different than the forces of ions with same conditions just in a nonpolar substance?

Answer 16

Since the D constant in water is higher than in nonpolar substances the force is water will be lower than the force in nonpolar substances.

Question 17

In nonpolar solvents (low D constant) what happens to ions?

Answer 17

ions of opposite charge attract each other so strongly they coalesce to form salt

Question 18

In water (high D) what happens to ions?

Answer 18

There is weaker force between the ions in water solution which permits significant quantities of the ions to remain separated.

Question 19

When is an ion said to be solvated?

Answer 19

When an ion in a polar solvent attracts the oppositely charged end of the solvent dipoles. The ion is thereby surrounded by several concentric shells of orientated solvent molecules. which are then said to be solvated

Question 20

The electric field produced by solvent dipoles do what?

Answer 20

oppose that of the ion so in effect the ionic charge is spread over the volume of the solvated complex.

Question 21

Why do polar solvents have high dielectrical constants?

Answer 21

The electrical field produced; electrical field opposes that of the ion so in effect the ionic charge is spread over the volume of the solvated co

Question 22

The orienting effect of ionic charges on dipolar molecules is opposed by what?

Answer 22

thermal motions with continually tend to randomly orientate all molecules thus dipoles in solvated complex are only partially orientated

Question 23

Why is the D constant higher for water than for other polar substances with comparable dipole moment’s?

Answer 23

liquid’s water hydrogen bond structure permits it to form orientated structures that resist thermal randomization, thereby more effective distributing ionic charges.

Question 24

Solubilities of polar and ionic substances are in enhanced if what?

Answer 24

Carry functional groups that can form hydrogen bonds with water such as

• Hydroxyl (-OH)
• Keto (-C=O)
• Carboxyl (-CO2H or COOH)
• or amino (-NH2)

Question 25

Fatty acids are what?

Answer 25

amphiphiles

Question 26

What happens when an electrical current is passed through an ionic solution?

Answer 26

The ions migrate towards the electrode of opposite polarity at a rate proportional to the electrical field and inversely proportional to the frictional drag experienced by the ions as they move through the solution

Question 27

What is the main reason the hydronium ion (H3O+) has such a high migration rate?

Answer 27

Proton jumping; protons can jump rapidly from one water molecule to another