Periodic Table And Energy

Question 1

what is enthalpy change

Answer 1

the heat transferred in a reaction at constant pressure

Question 2

what is an exothermic reaction

Answer 2

releases energy into the surroundings
negative enthalpy change

Question 3

what is an endothermic reaction

Answer 3

absorbs energy from the surroundings
enthalpy change is positive

Question 4

what is activation energy

Answer 4

the minimum amount of energy needed to begin breaking reactant bonds and start a chemical reaction

Question 5

what are the standard conditions

Answer 5

298K
100kPa

Question 6

what is standard enthalpy change of reaction

Answer 6

the enthalpy change when the reaction occurs in the molar quantities shown in the chemical reaction, under standard conditions

Question 7

what is standard enthalpy change of formation

Answer 7

the enthalpy change when 1 mole of a compound is formed from its elements in their standard states, under standard conditions

Question 8

what is standard enthalpy change of combustion

Answer 8

the enthalpy change when 1 mole of a substance is completely burned in oxygen, under standard conditions

Question 9

what is standard enthalpy change of neutralisation

Answer 9

the enthalpy change when an acid and an alkali react together, under standard conditions, to form 1 mole of water

Question 10

is energy released or absorbed in bond forming

Answer 10

released, so is exothermic

Question 11

is energy released or absorbed in bond breaking

Answer 11

absorbed, so is endothermic

Question 12

whatis q=mc^T

Answer 12

q=heat lost or gained
m=mass of water
c=specific heat capacity- 4.18
^T= change in temperature

Question 13

what are the rules of hess’s law

Answer 13

route 1=route 2
enthalpy change of reaction + sum of enthalpy change of formation (reactants)= sum of enthalpy change of formation (products)
enthalpy change of reaction= sum of enthalpy change reaction of products- sum of enthalpy chnage of reaction for reactants

Question 14

formula for enthalpy chnage of reaction

Answer 14

total energy absorbed- total energy released

Question 15

what conditions should there be in order for a reaction to takeplace (collision theory)

Answer 15

particles must collide in the right direction
must have the minmum activation energy

Question 16

why does a boltzmann distribution curve start at 0,0

Answer 16

as no particles have no energy

Question 17

where does increasing the temperature shift the boltzmann distribution curve to

Answer 17

-to the right
-more molecules have at least the activation energy
-total number of particles is the same so area under the graph is the same

Question 18

how does increasing concentration affect the reaction?

Answer 18

-increasing concentration means more particles so particles are closer together
-theyll collide more frequently
-more collisions= more chances to react

Question 19

how does increasing the pressure speed up the reaction

Answer 19

-particles are closer together, increasing the chance of successful collisions

Question 20

how does a catalyst increase rate of reaction

Answer 20

lowers the activation energy
more partciles will have enough energy to react

Question 21

what is a catalyst

Answer 21

a compound that increases the rate of reaction by providing an alternative parthway with a lower activation energy
catalyst is chemically unchanged

Question 22

what is a heterogenous catalyst

Answer 22

one that is in a different state from the reactants
the reaction happens on the surface of the heterogenous catalyst so increasing the surface area of the catalyst increases the amount of molecules that can react at the same time, increasing the rate of reaction

Question 23

what is a homogenous catatlyst

Answer 23

one that is in the same physical state as the reactants
works by forming intermediate species, reactants combine with the catalyst to make an intermediate species which then reacts to form the products and reform the catalyst

Question 24

what is the formula for rate of reaction

Answer 24

rate of reaction= amount of reactant used or product formed/ time

Question 25

how to investigate reaction rate- change in mass

Answer 25

when reaction starts set a stop clock or timer take mass measurements from balance in set time intervals make a column to record data in

Question 26

how to investigate reaction rate- volume of gas

Answer 26

use a gas syringe measure the volume of gas formed at set time intervals

Question 27

what is dynamic equillibrium

Answer 27

when the forward reaction goes at the same rate as the backwards reaction, concentrations of reactants and products stays the same

Question 28

what is le chateliers general principle

Answer 28

if theres a change in concentration, pressure or temperature the equillibrium will move to help counteract the change

Question 29

how does concentration affect equillibrium

Answer 29

increasing conc of reactant causes the equillibrium to try and get rid of the extra reactant does this by making more product, so shifts to the right increasing conc of product causes the equillibrium to try and get rid of the extra product makes the reverse reaction go faster decreasing the concentration has the opposite effect

Question 30

how does temperature affect the equillibrium

Answer 30

increasing temp means adding heat, equillibrium shifts towards the endothermic direction to absorb the heat decreasing temp means removing heat, equillibrium shifts towards the exothermic direction to replace the heat

Question 31

how does pressure affect equillibrium

Answer 31

increasing the pressure shifts the equillibrium to the side with fewer gas molecules which reduces the pressure decreasing the pressure shifts the equillibrium to the side wiht more molecules raises the pressure

Question 32

what affect does a catalyst have on equillibrium

Answer 32

no effect speeds up the reactions forward and backwards the same amount but cannot increase yield or change the position of equillibrium

Question 33

what is the equillibrium constant

Answer 33

aA+bB=dD+eE Kc=(D)^d x (E)^e / (A)^a x (B)^b

Question 34

what is the test for carbonates? + ionic equation

Answer 34

-add dilute hydrochloric acid to the sample -if carbonate is present carbon dioxide will be produced -test for CO2 using limewater -CO2 turns limewater cloudy CO3 2-(s) + 2H+(aq) ---> CO2(g) + H2O(l)

Question 35

what is the test for sulphates? +ionic equation

Answer 35

-add dilute hydrochloric acid -add barium chloride solution, BaCl2 -if a white precipitate has formed a sulphate ion is present Ba2+(aq) + SO42-(aq) ---> BaSO4 (s)

Question 36

what is the test for ammonium ions? +ionic equation

Answer 36

-add aqueous sodium hydroxide to the mixture and warm -use a damp piece of red litmus paper, if ammonium is present it will turn blue -the red litmus paper has to be damp so the ammonium gas can dissolve and make a colour change. NH4 +(aq) + OH-(aq) ---> NH3(g) + H2O (l)

Question 37

what is the test for halide ions +ionic equation

Answer 37

-add nitric acid, then silver nitrate solution, a precipitate will form if the halide ion is present silver CHLORIDE= WHITE precipitate silver BROMIDE= CREAM precipitate slver IODIDE= YELLOW precipitate Ag+ (aq) + X-(aq) --> AgX(s)

Question 38

when adding dilute and concentrated ammonia to the halides to distinguish between them, what is the results?

Answer 38

silver chloride- dissolves in both concentrated and dilute ammonia silver bromide- only dissolves in concentrated ammonia silver iodide- does not dissolve

Question 39

what is the correct testing order

Answer 39

carbonates sulphates halides