Energetics

Question 1

How to find enthalpy change?

Answer 1

H(pdts) - H(rxts)

Question 2

Standard conditions for enthalpy change.

Answer 2

298K, 10^5 Pa/ 1 bar

Question 3

Standard enthalpy change of combustion. (sign)

Answer 3

The enthalpy change when 1 mole of a substance is completely burnt in excess oxygen under standard conditions. (-)

Question 4

Standard enthalpy change of formation. (sign)

Answer 4

The enthalpy change when 1 mole of pure substance is formed from its constituent elements in their standard states under standard conditions.(+/-)

Question 5

Standard enthalpy change of neutralisation. (sign)

Answer 5

The enthalpy change when one mole of water is formed when an acid neutralises a base in an infinitely dilute aqueous solution under standard conditions. (-)

Question 6

Standard enthalpy change of atomisation. (sign)

Answer 6

The enthalpy change when 1 mole of isolated gaseous atoms are produced from the element in its standard state under standard conditions. (+)

Question 7

Standard enthalpy change of hydration. (sign)

Answer 7

The enthalpy change when 1 mole of gaseous ions is dissolved in a large amount of water under standard conditions. (-)

Question 8

Standard enthalpy change of solution. (sign)

Answer 8

The enthalpy change when 1 mole of solute is completely dissolved in a solvent to form an infinitely dilute solution under standard conditions. (+/-)

Question 9

First ionisation energy of an element. (sign)

Answer 9

The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to give 1 mole of gaseous ions with a single positive charge. (+)

Question 10

Lattice energy (sign)

Answer 10

Energy released when 1 mole of an ionic solid is formed from its isolated gaseous ions from an infinite distance apart. (+/-)

Question 11

Bond energy (sign)

Answer 11

The energy absorbed when 1 mole of covalent bonds between 2 atoms in a gaseous molecule are broken. (+)

Question 12

Electron affinity (sign)

Answer 12

The enthalpy change when 1 mole of gaseous atoms or negatively charged ions gain 1 mole of electrons. (1st E.A. -)(2nd E.A. +)