Enthalpy Changes

Question 1

What is the standard pressure used in enthalpy calculations

Answer 1

1atm/1x10^5pa

Question 2

Define the term bond enthalpy

Answer 2

Energy needed to break 1 mol of a bond in its gaseous state

Question 3

Given the equation:
H2(g) + i2(g) ➡️ 2HI(g)
What is the equation for bond enthalpy of I-I

Answer 3

I-I(g) ➡️ 2I(g)

Question 4

Why would a calculated enthalpy value differ to a substances real enthalpy

Answer 4

Bond enthalpies are mean values

Question 5

Definition of standard enthalpy of formation

Answer 5

Change in enthalpy during the formation of 1 mole of the substance from its constituent elements with all substances in there standard state

Question 6

Hess’s law

Answer 6

The total enthalpy change in a chemical reaction is a sum of the route by which the different chemical reactions involved takes place

Question 7

Standard enthalpy of combustion

Answer 7

The energy required to burn 1 mole of a substance completely in oxygen with all elements in standard conditions