4.1-4.2

Question 1

Assumption 1

Answer 1

Reactions are processes in which atoms that make up the reactants are rearranged, producing new substances.

Conservation of all atoms = mass & number of atoms

Question 2

Assumption 2

Answer 2

Rearranging atoms involves redistribution of electrons, changing potential energy of the particles. This explains why all chemical reactions involved the transfer of energy to the surroundings.

Question 3

Endothermic reactions

Answer 3

Reaction in which a large amount of energy must be input for the reaction to go forward
Reactants A have low PE and few configurations, Products B have high PE but more configurations.

Question 4

Exothermic reactions

Answer 4

Reaction in which little energy is required.

Reactants C high PE low configurations, Products D low PE high configurations.

Question 5

Assumption 3

Answer 5

For a reaction to occur, particles must collide. More collisions makes a faster process

Higher temp, higher pressure, higher concentration

Question 6

Assumption 4

Answer 6

Colliding particles must be oriented in a manner that allows reacting groups to interact effectively.

Question 7

Limiting reactant

Answer 7

A reactant of where there is too little according to the balanced chemical equation, causing an excess of another reactant

Question 8

Higher potential energy of a substance =

Answer 8

weaker bonds

Question 9

Configuration effectiveness

Answer 9

higher % of configurations leading to effective collision, faster process

In general,
1. fewer number of particles in gas phase that need to interact to generate particles
2. simpler the composition and structure of particles in the reactants

The faster the reaction goes

Question 10

Assumption 5

Answer 10

For a reaction to occur, particles must have enough energy to reach a transition state that leads to the formation of new products - activation energy

Catalysts - lower activation energy

Question 11

Assumption 6

Answer 11

As reactants interact to generate products, particles of the products may chemically react and regenerate particles of the reactants. The final state is determined by the balance between these two opposite processes.

Question 12

Reactant favored

Answer 12

There are more particles of the reactants than the products

Question 13

Product favored

Answer 13

There are more particles of the reactants than the products

Question 14

Reaction extent

Answer 14

Determined by activation energy, collision effectiveness of forward and backward reaction

Question 15

Conversion of reactants to products is close to 100% when…

Answer 15

the probability of forward reaction is much greater than the probability of the backward process during a cheical reaction

Question 16

Theoretical yield

Answer 16

The theoretical maximum amount of product in a chemical reaction assuming it goes to completion

Question 17

Case 1 (amounts of products)

Answer 17

There is only 1 reactant or all reactants are in excess except 1.

Question 18

In all experimental situations, there are losses in the amounts of product formed tue to a variety of reasons

Answer 18

1. Experiment (actual) yield will be different from theoretical yield.

actual/theoretical x 100 = % yield

2. If yield is 100%, we will produce less product or need more of a reactant to produce the desired amount of product.

Question 19

Case 2 (amounts of products)

Answer 19

If we are uncertain about which reactants are in excess and which is the limiting, we need to take systemic steps to identify it.

Question 20

Chelation

Answer 20

Chelating agents are capable of grasping metal ions - EDTA has six sites you can use

Question 21

Titration

Answer 21

Slowly adding a solution to a second solution until a stoichiometric equivalence is established

Question 22

Indicator

Answer 22

substance that undergoes a color change with a slight molar excess - point where it is observed is the end point - Eriochrome Black T

Question 23

Formation of EDTA

Answer 23

Ca2+ and EDTA4- = [Ca.(EDTA)]2-

Question 24

mL of EDTA to ppm of CaCo3

Answer 24

mL EDTA = 1L/1000mL = .005 M/L = 3.95 x 10^-5 mol CaCo3 = (3.95 x 10^5 mol CaCo3)/volume x 10^6

Question 25

Nitric acid

Answer 25

HNO3 = H+ and NO3-
strong acid, 100% dissociation

Question 26

Nitrous acid

Answer 26

HNO2 = H+ and NO2-
weak acid, HNO2 is mainly undissociated