Calorimetry Problems, Thermochemistry Practice, Specific Heat Capacity, Enthalpy Fusion, Chemistry

Bomb Calorimeter vs Coffee Cup Calorimeter Problem – Constant Pressure vs Constant Volume Calorimet

Enthalpy is the energy required to break a bond

Enthalpy is the same thing as the heat of the reaction

https://www.geeksforgeeks.org/enthalpies-for-different-types-of-reactions/

http://ch301.cm.utexas.edu/thermo/#enthalpy/enthalpy-all.php

7.68 | How does the bond energy of HCl(g) differ from the standard enthalpy of formation of HCl(g)?

Gibb’s Free Energy

-∆G tells you how many joules a reaction consumes or gives off

-negative ∆G indicates that the reaction gives off joules

ATP + H2O ⇌ ADP + Pi + 30.5 kJ/mol;     ∆G = -30.5 kj/mol

-positive ∆G indicates that the reaction consumes joules

Glucose + Pi ⇌ Glucose-6 Phosphate;     ∆G = 13.8 kJ/mol

-forward and reverse reactions have ∆G’s that are equal in magnitude but with opposite signs

-negative ∆G indicates that the reaction is spontaneous; positive ∆G indicates that the reaction is nonspontaneous

-∆G is determined by enthalpy and entropy modified by temperature

-the signs and quantities of enthalpy, entropy, and temperature determine if the reaction is spontaneous or not; many “trick” questions can be easily solved by knowing how to manipulate the ∆G equation

Gibbs Free Energy – Entropy, Enthalpy & Equilibrium Constant K

-∆G° is Gibb’s Free Energy under Standard State conditions

-standard conditions: 1 atm, 1 mole of reactants and products

-usually determined at 25 °C but doesn’t have to be

-1 atm because almost all reactions relevant to us is done under 1 atm (atmospheric pressure at sea level)

-NOT the same as standard temperature and pressure condtions (STP), which is a temperature of 273.15 °K (0 °C) and a pressure of 1 atm

-STP is used for gas reactions

-1 mole of gas takes up 22.4 L of volume

-so 1 mole = 22.4 L

-STP involves two variables (temperature and pressure), standard state involves two variables (moles and pressure)

-how to calulate ∆G° from formation ∆G°’s:

∆G° to Keq relationship:

–∆G of the overall reaction is NEVER related to the rate constant k. The rate constant k is only related to the ∆G of the transition state (ΔG‡). The ∆G of the overall reaction is never effected by changes in k, because ∆G is in joules AKA work, which is a state function and so does not depend on the path you take to get there.

-So even if you increase k and bring down ΔG‡, the overall reaction’s ∆G is unchanged

∆G° vs ∆G

-∆G° tells you how many joules a reaction gives off/consumes under 1 atm and 1 mole of each reactants and products

-∆G° also tells you about Keq. A negative ∆G° indicates that more products than reactants are present at equilibrium. A positive ∆G° indicates that more reactants than products are present at equilibrium

-∆G (non standard state) tells you how many joules a reaction gives off when you move away from 1 mole of reactants and products

-∆G is determined by adding the reaction quotient Q to ∆G°

-∆G° may be positive and show that the reaction is not spontaneous under standard conditions, but after lowering the amount of products and/or raising the amount of reactants, ∆G for the same reaction may be negative and show that the reaction is spontaneous

Standard State Gibbs Free Energy vs NonStandard State Gibbs Free Energy Thermodynamics Chemistry

-energy of a reaction can be obtained/required as the reaction moves from Q to Keq

-if Q < Keq, then the reaction will want to procede foward and have a negative ∆G

-the further Q is lower than Keq, the more negative ∆G is

-if Q > Keq, then the reaction will want to procede backwards and have a positive ∆G

-the further Q is higher than Keq, the more positive ∆G is

-once Q is at Keq, no free energy will be produced

-trick: imagine a number line

How Reaction Quotient vs Keq Determines NonStandard State Gibbs Free Energy (Neat Trick Chemistry!)

Coupling Reactions

-reactions can be coupled when they have similar substrates

-endergonic reactions are coupled to exergonic reactions to make an overall reaction that is favorable

Electrochemistry (Batteries)