Calorimetry - Introduction

Question 1

The two types of energy changes in chemical reactions can be classified by:

Answer 1

1. Exothermic Reactions - Give off heat energy
2. Endothermic Reactions - Absorb heat energy from their surroundings

Question 2

What is Enthalpy?

Heat Content

Answer 2

The chemical energy stored in a substance

Question 3

Ethalpy is often also reffered to as…

Answer 3

Enthalpy = Heat Content = H = Chemical Energy.

Energy can transform between chemical and heat energy. H measures that.

Question 4

Define Heat of Reaction

Answer 4

Symbol ΔH is Heat of reaction.
It is the change during chemical reaction.

Question 5

Give equation for ΔH

Answer 5

ΔH = H (products) - H (reactants)

Question 6

Describe ΔH for exothermic reactions

Answer 6

-ΔH - losses heat

Question 7

Describe ΔH for endothermic reactions

Answer 7

+ ΔH - gains heat

Question 8

What is a thermochemical equation

Answer 8

A balanced chemical equation that includes its heat of reaction (ΔH)

Question 9

What are the units used for ΔH?

Answer 9

J/mol or kJ/mol

Cannot write superscrip on here - ‘mol’ is usually denoted with power of negative 1

Question 10

Describe relationship between mole ration of equation and ΔH

Answer 10

Directly proportional - Doubling reactants and products in equation doubles ΔH and vice versa

Note: ΔH is also different for states, eg: changing water form liquid to gas has different ΔH than from solid to liquid

Question 11

Describe how Thermochemical equations can be manipulated?

Answer 11

They can be added or subtracted to produce new thermochemical equations.
Eg: Thermochemical equations for fusion (melting) + vaporisation (evaporation) = thermochemical equation for sublimation (solid to gas)