Reactivity 1

Question 1

Enthalpy

Answer 1

chemical potential energy of a system
delta H
delta H is positive when heat enters a system (endothermic reaction) - temperature of surroundings decreases
delta H is negative when heat leaves a system (exothermic) - temperature of surroundings increases

Question 2

law of conservation of energy

Answer 2

matter and energy can not be transferred in an isolated system
in a closed system energy can be transferred, not matter
potential to kinetic and vice versa
total energy always stays the same, cannot be created or destroyed

Question 3

Endo vs exothermic

Answer 3

Endo reactants are more stable that product
Exo products more stable than reactants
reactions tend to proceed in the energy of lowering energy/increasing stability

Question 4

Increase in temperature

Answer 4

• mass (m)
• heat added (q)
• nature of the substance
  q=mc*delta T
  c is specific heat capacity

Question 5

heat source of error

Answer 5

• heat loss to surroundings
• heat lost from system as soon as temperature rises above temperature of the surroundings
  remove part where heat is lost and work on assumptions:
  1) no heat loss from system
  2) all goes from reaction to water
  3) solution is dilute v(solution) = v(H2O)
  4) water has density of 1gcm^-3

Question 6

delta H

Answer 6

(mcdelta T of water)/no of moles of limiting reactant
for exothermic reaction m is negative
limiting reactant -

Question 7

bond enthalpy

Answer 7

energy required to break one mole of bonds in gaseous molecules under standard conditions
enthalpy of reactants - products

Question 8

Standard conditons for bond enthalpy

Answer 8

25 degrees C and 1x10^5 Pa

Question 9

entropy

Answer 9

measure of the dispersal or distribution of matter/or energy in a system

Question 10

first ionization energy

Answer 10

amount of energy required to remove one mole of electrons from one mole of gaseous atoms (generally endothermic)

Question 11

first electron affinity

Answer 11

enthalpy change when one mole of gaseous atoms attracts one mole of electrons to form one mole of gaseous ions (generally exothermic)