Chem class 2

Question 1

explain the difference between σ and π

Answer 1

Sigma σ bonds are the result of end to end overlap of orbitals and make single bonds.

**Pi π ** bonds are the result of side to side overlap of open rules and result in double and triple bonds.

Question 2

Sp hybridized carbon atoms

Answer 2

Have two groups bonded to them and have 180° bond angle between those groups

Question 3

sp2

Answer 3

Carbon atoms have three groups bonded 120° apart

Question 4

sp3

Answer 4

Carbons have four groups bonded 109.5° apart

Question 5

Covalent bond

Answer 5

Is formed between atoms when each contributes one or more of its unpaired valence electrons. The electrons are shared by both atoms to help complete both octets.

Question 6

Lewis base

Answer 6

Is a Nucleophile/ligand that donates a pair of electrons

Question 7

Lewis acid

Answer 7

Except a pair of electrons and is a electrophile (electron loving)

Question 8

Ionic bonds

Answer 8

Form between elements with large differences in electronegativity metals + nonmetals.

Strength of the bond depends on the charge and size of the ions, larger charges and smaller ions make the strongest ionic bonds.

Question 9

what element can hydrogen bond

Answer 9

F, O, N

Question 10

First law of thermodynamics

Answer 10

**The total energy of the universe is constant. **Energy may be transformed from one form to another, but it cannot be created or destroyed.

No transformation of energy is possible.

Question 11

Thermodynamics

Answer 11

THE TRANSFORMATION OF ENERGY FROM ONE FORM TO ANOTHER.

Question 12

Describe energy flowing in and out of the system

Answer 12

1. When energy flows into a system from the surroundings, the energy of the system increases and the energy of the surroundings decreases.
2. When energy flows out of a system into the surroundings the energy of the system decreases and the energy of the surrounding increases.

Question 13

Enthalpy; H

Answer 13

Is a measure of the heat energy that is released or absorbed when bonds are broken and formed during a reaction that run at constant pressure.

When a bond is formed energy is released ∆H <0

Energy must be put into a bond to break it ∆H >0

∆H is know as HEAT of rxn

Question 14

Exothermic

Answer 14

∆H is negative

**Products are in a lower energy state than reactants and the products have stronger bonds **

Question 15

Endothermic

Answer 15

**∆H is positive

Products are in a higher energy state than the reactants and have weaker bonds.**

Question 16

What contributes to the change in enthalpy of a chemical rxn?

Answer 16

Phase change
Formation of stronger intermolecular forces
Breaking covalent bonds

Question 17

Standard conditions of temperature and pressure

Answer 17

298 K (25° C)

pressure is 1 atm

STP is 0°

Question 18

Hess’s Law

Answer 18

A + B –> AB ∆H= - neg exo
Energy is released to make a bond

AB–> A + B ∆H= + pos end
Energy is needed to break a bond

Question 19

Second law of thermodynamics

Answer 19

The disorder of the universe increases in a spontaneous process.

All processes tend to run in a direction that leads to Maximum disorder.

Question 20

Entropy

Answer 20

The measure of disorder or randomness

S
∆S

Question 21

Positive ∆S

Answer 21

I is when randomness increases or order decreases

AB–> A + B

Question 22

Neg ∆S

Answer 22

If randomness decreases or order increases

A + B –> AB

Question 23

Entropy rules

Answer 23

1. Liquids have more entropy than solids
2. Gases have more entropy than solids or liquids
3. Particles in solution have more entropy than undissolved solids
4. Two moles of a substance have more entropy than one mole

Question 24

With the freezing of a liquid have a negative or positive ∆S?

Answer 24

negative

Question 25

A gas undergoes condensation. What’s true about the process

Answer 25

∆H is negative and ∆S is negative

Question 26

Third law of thermodynamics

Answer 26

Zero entropy. At absolute zero, thermal energy is absent and only the least energetic thermodynamics state is available to the system in question.

Lowest achievable temperature.

Question 27

Gibbs free energy

Answer 27

∆G= ∆H-T∆S

Question 28

∆G<0

Answer 28

Spontaneous in the forward direction

Question 29

∆G>0

Answer 29

Nonspontaneous in the forward direction

Question 30

∆G=0

Answer 30

Reaction is at equilibrium

Question 31

-∆H +∆S -∆G

Answer 31

**Reaction is spontaneous **

Question 32

+∆H +∆S -∆G

Answer 32

Reaction is spontaneous at high temperature

Question 33

+∆H +∆S +∆G

Answer 33

Reaction is non-spontaneous at low temperature

Question 34

-∆H -∆S +∆G

Answer 34

Reaction is non-spontaneous at high temperature

Question 35

-∆H -∆S -∆G

Answer 35

Reaction is spontaneous at low temperature

Question 36

+∆H -∆S +∆G

Answer 36

Reaction is non-spontaneous

Question 37

Exothermic

Exergonic

Answer 37

negative

Products have lower free energy than reactants

Question 38

Endothermic

Endergonic

Answer 38

Positive

Products have higher free energy than the reactants

Question 39

Aside from mercury, why does all transition metal elements have higher melting points than Group I metals?

Answer 39

Transition metal elements can have both d and s electrons delocalized.

Question 40

Metals readily absorb and conduct heat primarily because___________

Answer 40

the heat energy is absorbed by delocalized electrons as kinetic energy.

Question 41

What is the shape of the nitrate ion?

Answer 41

Trigonal planar

An atom that has three groups of atoms and no lone pairs has a trigonal planar geometry.

Question 42

What is the shape of the carbonate ion, CO3^2– ?

Answer 42

Trigonal planar

Question 43

Coordination complexes

Answer 43

Coordination complexes are covalently bonded complexes between nonmetal ligands and a transition metal ion.

Question 44

The shape of urea is

Answer 44

trigonal planar

Question 45

Polar covalent bond has what characteristic?

Answer 45

ionic