ch 12 practice. Flashcards
Which of the following substances have dipole-dipole bonds?
carbon dioxide
sulfur dioxide
water
oxygen gas
sulfur dioxide
water
Consider each pair of substances. Which one would have the strongest dispersion forces?
a. oxygen or xenon
b. carbon dioxide or sulfur dioxide
c. bromine or iodine
d. lithium or potassium
a. xenon
b. sulfur dioxide
c. iodine
d. potassium
Look for atom/molecule with largest no of electrons
Gas A has only dispersion forces
Gas B has dispersion forces and dipole-dipole forces.
If the gases have approximately the same Molecular mass,
Which would you predict has the highest boiling point?
Why ?
Gas B because it has stonger forces holding the particles together
Gas A has a boiling point of -78 C
Gas B has a boiling point of -44 C
Which gas would have the highest vapour pressure at 0 C ?
Which gas has the strongest intermolecular forces?
Gas A
Gas B
Why is water a bent molecule and not linear?
The carbon has 4 areas of electrons, two lone pairs and two single bonds to a hydrogen.
The lone pairs are ignored, so the molecule is said to be bent, not tetrahedral.
Gas X has a lower vapour pressure at -50 C than Gas Y.
Which gas would have stronger intermolecular bonds?
Gas X
What does VSEPR theory stand for?
Valence Shell Electron Pair Repulsion theory
What are the three primary (major) types of bonding?
Metallic
Covalent
Ionic
Covalent Molecular substances have 3 types of secondary bonding called …
dispersion
dipole-dipole
Hydrogen bonding
Why can Iodine be solid at room temp even though it only has dispersion forces between the molecules?
Large molecules/atoms have significant dispersion forces as the have more and larger temporary dipoles.
Water is a liquid at room temp while Ammonia is a gas.
What does this tell you about
a. The vapour pressure of each compound?
b. The strength of the secondary bonds for each substance?
c. The boiling point of each substance.
a. Ammonia has a higher VP
b. Water has stronger sec bonds.
c. Ammonia has a lower BPt or Water has a higher BPt
What is the VSEPR theory used for?
To predict the shape of molecules.
What is the main principle the VSEPR theory ?
Negatively charged electron pairs in the outer shell of an atom repel each other - they will try to get as far away from each other as possible ( 3D)
What is the Octet rule?
In covalent molecules, most atoms are most stable if they have 8 electron in their valence shell
(H needs 2 electrons)
What does a line represent in a Lewis diagram?
a chemical bond of 2 electrons.
