chemistry term 2 [exam]

Question 1

What are the 4 factors effecting rate of reaction

Answer 1

Agitation
Sub-division
Concentration
Temperature

Question 2

Describe Agitation

Answer 2

Mixing + stirring reaction mixture (speeds up), exposes unreacted particles, removes build-up of solid/bubbles covering reactant

Question 3

Describe Sub-division

Answer 3

Cutting up reactant exposing additional surface area, increase frequency of collision per second, smaller particles = faster reaction rate

Question 4

Describe Concentration

Answer 4

As concentration increases, more particles in given volume, more particle collisions per second

Question 5

Describe Temperature

Answer 5

Increases the number of collisions per second, increase the amount of energy the particles have.

Particles at a higher temp have more kinetic (moving) energy. = higher frequency of collisions

When particles have more kinetic energy, greater % of collisions will have sufficient energy to be successful. Therefore, increase in reaction rate.

Question 6

Describe collision theory

Answer 6

Particles must collide with a favourable orientation and have sufficient energy to break existing bonds (activation energy).

Insufficient energy and the particles bounce off each other, sufficient energy and they will react. If incorrect orientation (e.g. oxygen -> oxygen) no reaction, correct orientation (e.g. carbon -> oxygen) reaction occurs.

Question 7

When measuring reaction rates what does decrease in mass reflect

Answer 7

reflects change in reactants or products
The slope of the graph reflects the rate of the reaction:
 high gradient = fast reaction
 low gradient = slow reaction

Question 8

When measuring reaction rates what does curve indicate

Answer 8

Curve indicates that the reaction rate is not constant but slows down/speeds up

Question 9

Describe the structure of atoms in term of the electron shell

Answer 9

1st shell: Holds 2 electrons
2nd shell: Holds 8 electrons
3rd shell: Holds 18 electrons

The capacity of a shell formula: 2n2 [n = shell number]

Question 10

What are valence electrons

Answer 10

The outer shell electrons.
e.g. Mg = 2,8,2 valence = 2
(no more than 8 in outer shell)

Question 11

Explain periods

Answer 11

Periods (rows): Period number = number of electron shells

Question 12

Explain groups

Answer 12

Groups (columns): Group number = number of valence electrons
(only applies to group 1,2,13,14,15,16,17,18)

Valence electrons is last digit of group.
E.g. group 13 = 3 valence electrons

Question 13

In terms of metals, what is group 1

Answer 13

Alkali Metals

Question 14

In terms of metals, what is group 2

Answer 14

Alkali Earth Metals

Question 15

In terms of metals, what is group 17

Answer 15

Halogens

Question 16

In terms of metals, what is group 18

Answer 16

Noble gases

Question 17

How many valence electrons in group 1

Answer 17

1 (Lose 1e-)

Question 18

How many valence electrons in group 2

Answer 18

2 (Lose 2e-)

Question 19

How many valence electrons in group 17

Answer 19

7 (Gain 1e-)

Question 20

What is the charge on ions in group 1

Answer 20

+1

Question 21

What is the charge on ions in group 2

Answer 21

+2

Question 22

What is the charge on ions in group 17

Answer 22

-1

Question 23

What are the properties in group 1

Answer 23

-Soft metal -Shiny when cut -Low melting point -Highly Reactive -React violently with water -Down the group, more reactive

Question 24

What are the properties in group 2

Answer 24

-Relatively soft -Low melting point -Very reactive -React with water -Down the group, more reactive

Question 25

What are the properties in group 17

Answer 25

-F and Cl are gases -Br is liquid -I and At are solids -Down the group less reactive

Question 26

What are the properties in group 18

Answer 26

-Stable arrangement -Full outer shells -Unreactive -Gases at room temperature