Calorimetry - Redox rxn

Temperature Equilibrium

It is the final temperature that objects in contact will reach when they are in thermal equilibrium

Formulas for Temperature Equilibrium

• Q꜀ₒₒₗ = - Qₕₒₜ

• M꜀Cp꜀ (Tf - Ti)꜀ = - MₕCpₕ(Tf-Ti)ₕ

Calorimetry

• The science of the accurate measurements of amounts of heat and the accompanying temperature changes of an observed body when it releases or absorbs heat

• The measurements of the amounts of heat transferred to or released from a substance underlying physical or chemical process

Calorimeters

Calibrated Devices

Exothermic Reaction

The heat produced by the reaction is absorbed by the solution, which increases its temperature.

Endothermic Reaction

The heat required is absorbed from the solution, which decreases temperature

Constant-pressure calorimeter/ coffee-cup calorimeter

• a simple device used to measure the heat of a chemical reaction at constant pressure

• two nested styrofoams

• frequently used in determining the specific heat of solids or in studying reactions in aqueous solution.

• the pressure inside the calorimeter is basically equal to the pressure of the surroundings.

Formulas for Coffee-cup Calorimeter

• Qᵣₓₙ + Qₛₒₗᵤₜᵢₒₙ = 0

• Qᵣₓₙ = - Qₛₒₗᵤₜᵢₒₙ

• Qₘₑₜₐₗ = - Qᵥᵥₐₜₑᵣ

• Q = MCpΔT

Constant-Volume Calorimeter/ Bomb Calorimeter

• is a type of calorimeter that operates at a constant volume

Formulas for Bomb calorimeter

• Qᵣₓₙ = - (Q꜀ₐₗ + Qᵥᵥₐₜₑᵣ )

• Q = MCpΔT

• Q꜀ₐₗ = C꜀ₐₗ ΔT

Ccal

heat capacity of the calorimeter

Enthalpy

Chemical Energy involved in the heat flow of chemical reaction between the reactants and products

The change in enthalpy (ΔH)

is the amount of heat flow in a system for reactions carried out at constant pressure.

Enthalpy of Combustion

KJ/mol

Redox Reaction

Comes from the two words Reduction - Oxidation reactions

Cations

is a positively charged ion, formed when an atom loses one or more electrons

Atomic number

Represents the number of protons in an atom

Anion

is a negatively charged ion, Formed when an atom gains one or more electrons

Redox Reactions

is a type of chemical reaction wherein there is a transfer of electrons from one substance to another causing a change in their oxidation states.

Reduction

• is the gain of electrons in chemical reactions

• more negatively charged

• Decreases oxidation number

Oxidation

• is the loss of electrons in a chemical reaction

• more positively charged

• Increases oxidation number

Reducing Agent

• oxidized substance

• donates electrons

Oxidizing agent

• reduced substance

• accepts electon

Always in Reactants side

Where can we find the reducing/oxidizing agent as well as the oxidized/reduced substance?

Memorize

Oxidation number

is the total number of electrons that an atom will either gain or lose in order to form a chemical bond with another atom.

metals

• cations

• tends to lost electrons to become positively charged

nonmetals

• anions

• tends to gain electrons to become negatively charged

Group 18

• noble gas have zero oxidation number