Physical chemistry

Question 1

define enthalpy change

Answer 1

the heat energy transferred in a reaction at standard conditions (constant pressure)

Question 2

what is the standard pressure condition ?

Answer 2

100kPa (about 1 atm)

Question 3

what is the standard temp condition ?

Answer 3

298K

Question 4

name an exothermic reaction

Answer 4

combustion

Question 5

name an endothermic reaction

Answer 5

thermal decomposition

Question 6

what is the symbol for activation energy ?

Answer 6

Ea

Question 7

what is standard enthalpy change of reaction ?

Answer 7

E.C. when reaction occurs in molar quantities shown in the chemical equation, under S.C.

Question 8

what is standard enthalpy change of formation ?

Answer 8

E.C. when 1 mole of a compound is formed from its elements in their standard states, under S.C.

Question 9

what is standard enthalpy change of combustion ?

Answer 9

E.C. when one mole of a substance is completely burned in oxygen, under S.C.

Question 10

what is standard enthalpy change of neutralisation ?

Answer 10

E.C. when an acid and an alkali react together, under S.C., to form 1 mole of water

Question 11

to break bonds, energy is …

Answer 11

needed

Question 12

to make bonds, energy is …

Answer 12

released

Question 13

describe the bonds in endothermic

Answer 13

bonds are broken

Question 14

describe the bonds in exothermic

Answer 14

bonds are formed

Question 15

what is bond dissociation enthalpy ?

Answer 15

amount of energy needed to break bonds per mole

Question 16

what to remember with enthalpy change reactions

Answer 16

the sign (+ or -)

Question 17

what is Hess’s law ?

Answer 17

total enthalpy change is always the same, no matter which route is taken

Question 18

what is the standard change of formation of any element ?

Answer 18

0