equilibrium keywords

Question 1

bond energy/ bond enthalpy

Answer 1

the energy needed to break 1 mole of a particular bond in 1 mole of gaseous molecules.

Question 2

enthalpy change of formation

Answer 2

the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions (at 25 oC 1 atm).

Question 3

sign of enthalpy change of formation

Answer 3

can be (+) can be (-)

Question 4

enthalpy change of combustion

Answer 4

the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions (at 25°C 1 atm).

Question 5

sign of enthalpy change of combustion

Answer 5

always (-)

Question 6

enthalpy change of hydration

Answer 6

the enthalpy change when 1 mole of a specified gaseous ion dissolves in sufficient water to form a very dilute solution.

Question 7

sign of enthalpy change of hydration

Answer 7

always (-)

Question 8

enthalpy change of atomisation

Answer 8

the enthalpy change when an element or a molecule is converted into 1 mole of free gaseous atoms under standard conditions (at 25°C 1 atm).

Question 9

sign of enthalpy change of atomisation

Answer 9

always (+)

Question 10

enthalpy change of neutralisation

Answer 10

the enthalpy change when 1 mole of water is formed from the neutralisation between acid and alkali under standard conditions (at 25°C 1 atm).

Question 11

sign of enthalpy change of neutralisation

Answer 11

always (-)

Question 12

enthalpy change of solution

Answer 12

the energy absorbed or released when 1 mole of an ionic solid dissolves in sufficient water to form a very dilute solution.

Question 13

sign of enthalpy change of solution

Answer 13

can be (+) can be (-)

Question 14

Na+(g) + aqueous solution -> Na+(aq)

Answer 14

enthalpy change of hydration

Question 15

NH4Cl(s) + aq -> NH4+(aq) + Cl-(aq)

Answer 15

enthalpy change of solution

Question 16

Al(s) -> Al(g)

Answer 16

enthalpy change of atomisation

Question 17

1/2 O2(g) -> O(g)

Answer 17

enthalpy change of atomisation

Question 18

mean bond enthalpy

Answer 18

the energy needed in breaking (a) covalent bond(s) averaged for that type of bond over a range of molecules

Question 19

reversible reaction

Answer 19

a reaction in which products can be changed back to reactants by reversing the conditions

Question 20

dynamic equilibrium

Answer 20

in an equilibrium mixture, molecules of reactants are being converted into products (forward reaction) at the same rate as products are being converted to reactants (reverse reaction).

You have a reversible reaction in a state of dynamic equilibrium.

Question 21

suggest why something is very insoluble in water, besides if it having strong covalent bonds. in terms of enthalpy change.

Answer 21

its enthalpy change of solution is very positive

Question 22

standard enthalpy change of a reaction

Answer 22

Heat change measured at constant pressure measured at standard conditions