Lecture 3 (The effect of electrolytes on chem equilibrium)

What is the definition of chemical equilibrium?

It is when the RATE of a forward and reverse reaction are equal, resulting in constant concentrations of reactants and products.

What is Le Chatelier’s Principle?

If equilibrium is disturbed by either concentration, pressure, or temperature change, the system will shift (oppose) to counteract it.

What is the concentration of ions a driving factor of?

maintaining or distrubing equilibrium in systems like buffers, enzyme activity, and cellular signaling.

What is the equilibrium constant equation and what does it mean when K>1 or K<1?

K=[C][D]/[A][B] A + B → C + D

K>1: product formation favored in equilibrium

K<1: reactants favored in equilibrium

If a system has a K value of 4.0, does that mean the reaction goes to completion?

No, products are slightly favored at equilibrium. The reaction is considered incomplete

What is the equation for ionic strength?

I = 1/2 Σ (ci zi^2) where ci= concentration of each ion, zi=charge of each ion

What are the 2 effects of ion strength increasing?

1. increase shielding effect → decreasing effective concentration of ions involved in a chemical rxn

2. activity coeff decreases → decreases effectivity of ions in a chemical rxn

What is sodium essential for?

regulation of osmotic pressure and electrolyte balance in extracellular fluids

What is the bicarbonate buffer reaction?

CO2 + H2O → H2CO3 → H+ + HCO3-

How is sodium involved in the bicarbonate buffer reaction and what can happen in the case of hyponatremia?

Na+ binds w/ HCO3- → NaHCO3 (sodium bicarbonate) which neutralizes acid in blood.

Hyponatremia → metabolic acidosis due to lack of NaHCO3 transporters in the kidneys → disturb acid excretion efficiently

What is potassium essential for?

generating the resting membrane potential of cells

What does a potassium imbalance affect?

the electrochemical gradient across membranes → affecting action potential and muscle contraction

What can hyperkalemia cause?

makes resting membrane potential less negative → arrhythmias and potential cardiac arrest

What do calcium ions regulate?

enzyme activity, muscle contraction, blood clotting, and neurotransmitter release

What is calcium-phosphate equilibrium and what can hypercalcemia lead to?

Calcium-phosphate equilibrium: the balance of bone formation and the affect of enzyme functions

Hypercalcemia → kidney stones due to equilibrium shift in favor of calcium phosphate precipitates

What do chloride ions help maintain?

electroneutrality

Explain the chloride shift

CO2 enters blood → carbonic anhydrase converts to H2CO3 → H+ + HCO3- → HCO3- exits RBC, Cl- enters cell to maintain electroneutrality

Why do biological systems have complex chemical environments?

because multiple equilibria occur simultaneously in a network of interactions. a change in one equilibrium can have a cascading affect on others

What does solving multicomponent equilibria require?

a system of coupled nonlinear equations

What are the 3 standard methods used in the modeling of chemical systems?

mass balance: ensures total [ ] of each species (bound + free) is accounted for in the system

charge balance: ensures total charges of both + and -, essential for electrochemical equilibrium

equilibrium constant expressions: relate the [ ] of reactants and products at equilibrium, giving insight into the direction/extent of reactions