Bonding & Moles

Question 1

Where are intermolecular bonds found?

Answer 1

BETWEEN molecules

Question 2

Describe some features of intermolecular bonds

Answer 2

• weaker than INTRA
• significant effects on phase
• electrostatic attractions between opposite charges

Question 3

Name the 3 types of attractive forces

Answer 3

• induced dipole-induced dipole
• dipole - dipole
• hydrogen bonds

Question 4

What is a dipole-dipole interaction?

Answer 4

A type of intermolecular force between the permanent dipoles of 2 molecules, this occurs when the partially negative portion of one of the polar molecules is attracted to the partially positive portion of the second polar molecule.

Question 5

What is a van der waals bond?

Answer 5

an intermolecular (weak) bond which is caused by momentary changes in electron density in a molecule

Question 6

What are the only attractive forces present in nonpolar compounds?

Answer 6

• Van der waals

Question 7

What is meant by dipole?

Answer 7

An uneven electron distribution within a chemical bond

Question 8

What is a non polar compound?

Answer 8

Compounds that do not have slightly negative and positive charges within the compound.

Question 9

What is a polar compound?

Answer 9

Compounds that have slight charges (slightly positive and slightly negative) within the compound.

Question 10

What determines the strength of the van der waals interaction?

Answer 10

The surface area of a molecule, (the larger the surface area, larger the attractive force)

Question 11

When does polarization occur?

Answer 11

when a small cation (+) with high positive exchange or a large anion with high negative charge exerts a strong pull on the shared electrons and distorts the oppositely charged ion

Question 12

Which atoms have more loosely held valance and are more polarizable?

Answer 12

Larger atoms (smaller atoms have more tightly held electrons)

Question 13

What are the three elements hydrogen bonds typically occur between?

Answer 13

ON/F

• oxygen
• Nitrogen
• Fluoride

Question 14

What are the results of hydrogen bonding?

Answer 14

increase in the melting point, boiling point, solubility and viscosity

Question 15

What properties of water is hydrogen bonding responsible for?

Answer 15

• higher than expected boiling point
• high specific heat capacity
• ice is less dense than water

Question 16

Define boiling point

Answer 16

• the temperature at which liquid molecules in a compound are converted into gas (energy is needed to overcome attractive forces in the liquid state)

Question 17

In what order do the intermolecular forces increase in strength?

Answer 17

• van der waals (weakest)
• dipole-dipole
• hydrogen bonding (strongest)

Question 18

Define a mole

Answer 18

A number of individual entities hich links the mass in atomic mass units to the mass in grams

Question 19

What is molecular mass

Answer 19

This is the mass of one molecule of substance on the atomic mass scale.

Question 20

What is Avogrado constant?

Answer 20

the number of particles present in one mole of a substance

Question 21

Define a chemical bond

Answer 21

electrostatic attraction between nuclei and electrons

Question 22

How do you calculate the number of moles present in a substance?

Answer 22

mass/molar mass

Question 23

What is mass measured in?

Answer 23

grams (g)

Question 24

What are moles measured in?

Answer 24

mol

Question 25

What re the units for molar mass?

Answer 25

g mol -1

Question 26

The bigger the molar mass the bigger the _____ force

Answer 26

Van de waals

Question 27

When does a van de waals force form?

Answer 27

It results when the electrons in 2 adjacent atoms occupy the positions that make the atoms form temporary dipoles

Question 28

Whats the main difference between a dipole-dipole force and a van de waals force?

Answer 28

• dipole- dipole force occurs when a permanent dipole exists, van de waals occur between temporary dipoles
• dipole-dipole is a stronger force
• dipole-dipole force means the molecules with it have a higher boiling and melting point

Question 29

What is the significance of the elements ONF?

Answer 29

most electronegative elements in the periodic table

Question 30

What is avogrados number?

Answer 30

6.022 x 10^23

Question 31

What does the avogrados constant show?

Answer 31

that number of base units present in a mole of a particular compound is a constant value for any compound

Question 32

What does avogrados number show?

Answer 32

indicates the number of hydrogen atoms present in 1g of 1H of number of carbon atoms present in one gram of 12-C sample