DF - More on enthalpy changes

Question 1

What does an enthalpy level diagram show?

Answer 1

The enthalpy changes during a reaction.

Question 2

What is activation energy?

Answer 2

The minimum amount of energy needed to begin breaking reactant bonds and start a chemical reaction.

Question 3

Finish the statement about the stability of the substance:

The less enthalpy a substance has…

Answer 3

…the more stable it is.

Question 4

How do you use calorimetry to find out enthalpy change of combustion of a flammable liquid?

Answer 4

Set up apparatus.

As fuel burns it heats the water. You can work out heat absorbed by the water if you know the mass of the water, the temp change of the water and the specific heat capacity of water.

Question 5

How can calorimetry be used to calculate the enthalpy change for a reaction that happens in solution such as neutralisation?

Answer 5

Add a known volume of acid to an insulated container and measure the temperature.

Then add the known volume of alkali and record the temp rise. (Stir solution so it is evenly heated.)

The heat needed to raise the temp of the solution formed = the heat given out by the reaction.

Question 6

What is standard enthalpy change of neutralisation?

Answer 6

The enthalpy change when an acid and an alkali react together under standard conditions to form 1 mole of water.