exam semester 1

Question 1

what are spontaneous chemical reactions

Answer 1

reactions that occur at room temperature without the impact of energy such as heat or electricity
-occur at room temp
some quick, some slow

Question 2

whar are energy transformations

Answer 2

evident in changes in the temperature of surrondings and/or the emission of light

Question 3

chemical reactions

Answer 3

involce the creation of new substances and associated energy transformations

Question 4

what are some chemical equations

Answer 4

acid + sulphides —-> salt + hydrogen sulfide
acid + sulphite —–> salt + water + sulfur dioxide
water + active metal —-> salt + hydrogen
base + ammonium salt ——> salt + water + ammonia
base + non-metal oxide —–> salt + water

Question 5

what is a precpitation reaction

Answer 5

reaction when solid formed

Question 6

what are net ionic equations

Answer 6

Spectator ions are those ions that appear exactly the same on each side of the ionic equation.
dont effect the reaction

Question 7

what is moler mass

Answer 7

mass in grams of 1 mole of sustance
take the atomic mass of the element of the periodic table and multiply it by the amount of times it occure in the equation
top m
left n
right mr

Question 8

what is a mole

Answer 8

a counting unit

Question 9

where did the mole come from

Answer 9

the number of atoms in exactly 12g of carbon-12 isotope

the number of particles in one mole, 6.022 x 10^23, is known as auogadros constant or number

Question 10

what is the atomic mass

Answer 10

mass in grams of one mole of atoms in an element

Question 11

what is number of particles

Answer 11

refers to many things - atoms, ionic unit, or molecules - dependant on the substance
formula: n=#p/na
n=moles
na = auogadros constant

Question 12

what is stoichiometry

Answer 12

measures these quantitative relationships, and is used to determine the amount of products/reactants that are produced/needed in a given reaction.

Question 13

what must happen for a chemical reaction to occur

Answer 13

the bonds between the atoms in the reactants must be broken and new bonds between the atoms in the product must be formed

Question 14

what happens in an exothermic reaction

Answer 14

releases heat energy to the surrondings
the temperature of the surrondings increases
the energy released from forming new bonds is greater than the energy needed to break old bonds
(triangle) H is negative

Question 15

what happens in an endothermic reaction

Answer 15

takes in heat from surrondings
the temperature of the surrondings decreases
the energy needed to break old bonds is greater than the energy released from forming new bonds
(triangle) H s positive

Question 16

what requirements must be met before a chemical reaction will occur

Answer 16

the reacting particles must collide
they must collide with a specifc minimum amount of energy, called the activation energy
the particles must collide with a favourable orientation

Question 17

what is a succesful collision

Answer 17

has suffiecient energy and an appropiate orientation to allow old bonds to be broken and new bonds to be formed. this leads to the formation of products

Question 18

what is an unsuccesful collision

Answer 18

the energy and or orientation are not satisfactory. this doesnt lead to the formation of products

Question 19

what is the activated complex/transition state

Answer 19

a temporary, highly unstable structure that has more energy then either the reactants or products. it is the stage of maxium potential energy

Question 20

what is the activation energy

Answer 20

the miniumum amount of energy required for a reaction to occur

Question 21

what is enthalpy

Answer 21

the total energy possesed by a chemical substance

Question 22

what is an energy profile diagram

Answer 22

shows the enthalpy of the reactants, activated complex and products

Question 23

the number of successful collisons depends on

Answer 23

total number of collisions

percentage of collisions that are succesful

Question 24

what happens if the reactants only require a small amount of energy

Answer 24

the activation energy will be low

Question 25

how can you speed up the rate of reaction

Answer 25

increasing temperature, increasing surface area, increasing pressure, increasing concentration, adding a catalyst

Question 26

what happens when you increase the concentration in a reaction

Answer 26

the number of particles per unit increases
this increases the number of collisons, therefore increasing the number of succesful collisions and therefore increasing the rate of reaction

Question 27

what happens when you increase the pressure in a reaction

Answer 27

by increasing the pressure, the particles per unit volume increases
this increases the number of collisons, therefore increasing the number of succesful collisions and therefore increasing the rate of reaction

Question 28

what happens when you increase the surface area in a reaction

Answer 28

more of the solid is exposed and therefore more collsions are possible.
this increases the number of collisons, therefore increasing the number of succesful collisions and therefore increasing the rate of reaction

Question 29

what happens when you increase the temperature in the rate of reaction

Answer 29

the average kinetic energy of the particles is increased. therefore a greater proportion of particles have the minimum amount of energy to react and therefore increasing the rate of reaction

Question 30

what happens when you add a catlayst to a reaction

Answer 30

isnt used up in the reaction but is able to increase the rate of chemical reaction
it provides an alternate pathway with lower activation energy meaning a greater proportion of the particles have the required energy to react