energetics

Question 1

combustion

Answer 1

heat evolved when 1 mole of a substance is completely burnt in excess oxygen under the standard conditions of 298K and 1 bar. ( reactants- products)

Question 2

formation

Answer 2

heat change when 1 mole of substance is formed from its constituent elements in their standard states under the standard conditions of 298K and 1 bar ( products - reactants)

Question 3

lattice energy

Answer 3

heat evolved when 1 mole of solid ionic compound is formed from its gaseous ions ( always negative)

Question 4

LE on an ionic compound

Answer 4

the larger the ionic charges, the larger the magnitude of the lattice energy
the larger the ionic radii, the smaller the magnitude of the lattice energy

Question 5

entropy

Answer 5

a measure of degree of disorderliness in a system. the more disordered a system, the larger its entropy.

Question 6

mixing of particles

Answer 6

-entropy increases
-increase in disorderliness of the system since mixing results in
-more ways of arranging the particles and distributing the energy among the particles

Question 7

change in number of particles

Answer 7

-entropy increases
-increase in the disorderliness of the system
-increase in the number/ amount of gas particles (mol)
-more ways of arranging and distributing the energy among the particles

Question 8

change in temperature

Answer 8

• entropy increases
  -increase in the disorderliness of the system
  -increase in temperature increases the average kinetic energy of the particles
  -broadening of the Boltzmann energy distribution
  -more ways of distributing energy quanta

Question 9

bond energy

Answer 9

heat absorbed when 1 mole of a particular covalent bond between 2 atoms in the gaseous state is broken ( always +ve)

Question 10

ionisation energy

Answer 10

heat absorbed when 1 mole of electrons is removed from 1 mole of gaseous atom to form 1 mole of singly charged gaseous cations ( always +ve)