energetics

Question 1

what does system mean in a chem reaction

Answer 1

the atoms and bonds involved in the chem reaction

Question 1

what does system mean in a chem reaction

Answer 1

the atoms and bonds involved in the chem reaction

Question 2

law of conservation

Answer 2

amount of energy in an isolated system remains the same.
energy cannot be destroyed or created.
can only be transferred from one form to another

Question 3

what energy change is breaking bonds associated with

Answer 3

endothermic- energy is taken in

Question 4

what energy change is making bonds associated with

Answer 4

exothermic- energy is released to make bonds

Question 5

activation energy

Answer 5

minimum energy required for a reaction to take place

Question 6

standard T

Answer 6

298K
20 *C

Question 7

standard P

Answer 7

100kPa

Question 8

define enthalpy (H)

Answer 8

total energy contents of the reacting materials

Question 9

define enthalpy change

Answer 9

describe energy exchange that takes place with surroundings under standard conditions

Question 10

unit of enthalpy change

Answer 10

kJmol

Question 11

exothermic

Answer 11

energy released on bond formation in the products is greater than absorbed by breaking the bonds in reactants

Question 12

examples of exothermic reactions

Answer 12

combustion
neutralisation
metal displacement

Question 13

endothermic

Answer 13

energy needed to be absorbed to break bonds in the reactants is greater than the energy transferred to surroundings as bonds are made in products

Question 14

examples of endothermic

Answer 14

photosynthesis
thermal decomposition
cracking

Question 15

4 types of standard enthalpy change

Answer 15

reaction
formation
combustion
neutralisation

Question 16

define reaction standard enthalpy change

Answer 16

energy transferred when the molar quantities of reactants react under standard conditions

Question 17

define formation standard enthalpy change

Answer 17

1 mol of a product is formed from its elements under standard states and conditions

Question 18

example of formation SEC

Answer 18

H2 + 1/2 O2 -> H2O(l)

Question 19

what is the enthalpy change of a formation of an element always

Answer 19

0 kJmol

Question 20

define combustion standard enthalpy change

Answer 20

one mol of a substance burns completely in oxygen under standard conditions. must only be one mol of the fuel/reactant.

Question 21

is combustion endothermic or exothermic

Answer 21

exothermic

Question 21

is combustion endothermic or exothermic

Answer 21

exothermic

Question 22

which type of standard enthalpy change always produces one mol of product

Answer 22

formation

Question 23

which type of standard enthalpy change always uses 1 mol of reactant

Answer 23

combustion

Question 24

which type of standard enthalpy change always uses 1 mol of reactant

Answer 24

combustion

Question 24

which type of standard enthalpy change always produces one mol of water

Answer 24

neutralisation

Question 25

define neutralisation standard enthalpy change

Answer 25

energy change when acid and alkali in an equation for reaction neutralise eachother under standard conditions to form one mol of water

Question 26

what is the standard enthalpy change of neutralisation if a strong acid is used

Answer 26

-57 kJmol

Question 27

what is the standard enthalpy change of neutralisation if a weak acid is used

Answer 27

-55/56 kJmol

Question 28

what is the symbol for standard enthalpy change of neutralisation

Answer 28

△ₙH⦵

Question 29

what is the symbol for standard enthalpy change of formation

Answer 29

△ᶠH⦵

Question 30

what is the symbol for standard enthalpy change of combustion

Answer 30

△ᶜH⦵

Question 30

what is the symbol for standard enthalpy change of reaction

Answer 30

△ᵣH⦵

Question 31

equation to find amount of energy (q), step 1 in calculating enthalpy change

Answer 31

q=mc△T

Question 32

equation to find enthalpy change △H

Answer 32

△H=q/n

Question 33

what assumption do we make when using q=mc△T

Answer 33

we assume that 4.18 (SHC of water) is the SHC of a solution