Enthalpy

Question 1

what is enthalpy represented by

Answer 1

H

Question 2

what does enthalpy relate to

Answer 2

the bonds made and broken in a chemical reaction

Question 3

what is H1 in a reaction

Answer 3

the reactants

Question 4

what is H2 in a reaction

Answer 4

products

Question 5

what is ∆H

Answer 5

the change in enthalpy

Question 6

what = ∆H (whats the equation for ∆H)

Answer 6

∆H = enthalpy of products - enthalpy of reactants
(or)
∆H = H2 - H1§

Question 7

is ∆H +ve or -ve for an endothermic reaction

Answer 7

∆H is +ve

Question 8

is ∆H +ve or -ve for an exothermic reaction

Answer 8

∆H is -ve

Question 9

Can enthalpy be measured or calculated

Answer 9

no but enthalpy changes can be

Question 10

what would happen to ∆H if the reaction was reversible

Answer 10

the number for ∆H would be the same the sign would have changed from + to - or visa versa

Question 11

what is a reaction profile

Answer 11

it is a diagram of the enthalpy levels of the reactants and products in a chemical reaction

Question 12

what does the vertical axis (y) represent on a reaction profile

Answer 12

it is enthalpy but not ∆H

Question 13

what does the horizontal axis (x) represent on a reaction profile

Answer 13

it is progress of the reaction, reaction coordinate or extent of reaction

Question 14

is the product line higher or lower on a reaction profile in an endothermic reaction

Answer 14

higher

Question 15

is the product line higher or lower on a reaction profile in an exothermic reaction

Answer 15

lower

Question 16

what is the difference between the product line and the reactant line in a reaction profile

Answer 16

∆H

Question 17

what is ∆H for an endothermic reaction

Answer 17

+ve

Question 18

what is ∆H for and exothermic reaction

Answer 18

-ve

Question 19

how is the reaction pathway shown on a reaction profile

Answer 19

it is shown by a line from the reactants to products on a reaction profile

Question 20

what is the reaction pathway

Answer 20

the route in terms of enthalpy from reactants to products

Question 21

what is required in reaction pathways before new bonds can form in the products

Answer 21

an input of energy to break bonds

Question 22

where is the activation energy in a reaction profile

Answer 22

the maximum height of the pathway above the enthalpy level of the reactants

Question 23

what are standard conditions represented by

Answer 23

the symbol ⦵

Question 24

where is the symbol ⦵ used

Answer 24

after ∆H to show that the reaction is conducted under standard conditions

Question 25

what are standard conditions (⦵)

Answer 25

100 kPa pressure and a stated temperature

Question 26

what is the standard enthalpy of combustion if 2 moles of fuel is combusted

Answer 26

the standard enthalpy of combustion multiplied by 2

Question 27

in an enthalpy of combustion reaction what is the most common error

Answer 27

heat loss