Chapter 1 : pH and Buffers Flashcards
Types of Chemical Bonds
- Ionic
- Covalent & Polar covalent
- Hydrogen
- Van der Waals
What type of bond is water ?
Polar Covalent .
The oxygens have a slight (-) charge while the hydrogens have a a slight (+) charge creating a difference in charge.
What is the universal law for solvents
” Like dissolves like”
polar molecules dissolve in polar solvents vice versa
Ionic compounds can create crystal structures called
Salts
Why do salts dissolve easily in water?
The positive part of water molecules attracts the negative chloride ions and the negative part of water molecules attracts the positive sodium ions.
Water has the highest interaction with what type of molecule ?
Polar molecules
Why do water molecules create “ cages” around non-polar molecules ?
Non- polar molecules
(CH bonds ) usually have no charge. Thus hydrogen bonds with itself to surround the molecule
In a low entropy state , water molecules are
highly ordered and structured
In high entropy states,water molecules are
less ordered and structured. Most are freely moving
What is an amphiphilic molecule ?
Molecules that are both polar and non-polar
Ex: fatty acids, phospholipids, micelles
How are fatty acids amphiphilic ?
The tails are nonpolar with CH bonds and the heads are polar with the hydrogen bonds
Why is the polarity of phospholipids so important
It helps to form the extracellular matrix or cell transport
H+ can also be represented as
H3O (+)
In acidic conditions , hydronium ions combine to form
H(+) + H20 -> H30(+)
In basic conditions, hydronium ions combine to form
H20 -> H(+) + OH (-)
What is the concentration of H+ at equilibrium ?
H+ = 1 x 10 ^(-7) M OH = 1 x 10 ^(-7) M
What is the concentration of H+ at acidic conditions?
H+ is greater than 1 x 10 ^(-7) M
OH is less than 1 x 10 ^(-7) M
What is the concentration of H + at basic conditions ?
OH is greater than 1 x 10 ^(-7) M
H(+) is less than 1 x 10 ^(-7) M
The Keq constant always adds up to
1 x 10 ^(-14) M
What is the Keq constant equation for water ?
Keq = [ H+] [OH-] ÷ [H20]
What is Kw
Kw = ionization of water constant which is 1 x 10 ^(-14) M
What is pH
ratio of H+ concentration vs OH- concentration. It is also based on the logarithmic scale.
What is the logarithmic equation for pH ?
pH = (-)log10[H+]
What are electrolytes ?
substances that when dissolved in water, conducts an electric current
Examples of of electrolytes
- Salts ( NaCl )
- Strong acids (HCL)
- Strong bases
( NaOH )
What is the general equation for Keq
Products/ Reactants
What is Ka
The acid disassociation constant
What is the Ka equation ?
Ka = [H+] [A-] ÷ [HA]
True or false, weak electrolytes dissociate completely
False
Examples of weak electrolytes
Nitric acid : HNO3
Acetic acid : CH3COOH
The higher the Ka….
The more the compound disassociates. The pKA is also inversely lower
Henderson Hasselbalch equation
pH = pKA - log
( [HA]/ [A] )
What does the Henderson Hasselbalch equation tell us ?
- the relationship between the dissociation of weak acid and pH
- helps to calculate the pH or pKA
If half the acid is disassociated,
[HA] =[ A] or pH= pKA
What is titration ?
A method used to determine the amount of acid in a solution by adding incremental amounts of base .
What happens when more base is added to a solution
More OH combines with H+ causing more acid disassociation from the water formation . pH increases.
Where is the halfway point in a titration curve
Where the pH= pKA
or the flat line in the middle of the graph
The higher the pKA ,..
the lower the Ka , and the harder it is for H+ to dissociate
Polyprotic acids
Acids that have more than one H+ to lose . On the titration cure , each flat line indicates when an H+ is lost
Examples of Polyprotic acids
H3PO4 - phosphoric acid
H2SO4 - sulfuric acid
What is a buffer
Something used to help maintain solutions within a certain pH range by absorbing excess H+ or OH
The pH range for a buffer is around the
pKA
What is a common buffer used in intracellular fluid
Phosphate is used in the body as it is used for cellular transport
What is another example of a buffer system in the body
Histidine buffer system ( amino acid)
What is the buffer system used in blood circulation
Bicarbonate buffer system from carbonic acid ( H2CO3) to bicarbonate ( HCO3)
What is the 1st law of thermodynamics ?
Energy cannot be created or destroyed, simply conserved and transformed
The change in internal energy of a system is equal to
the amount of energy absorbed by the system in the form of heat and the work performed on the system through its surroundings
Energy Conservation Equation
ΔE = q + w
Energy is equal to the total amount of heat and work
What is enthalpy
The total amount of heat or energy in a system . Or change of energy in a reaction.
In chemical and biochemical reactions, pressure is
constant
What is the 2nd law of thermodynamics
Systems tend to proceed from ordered ( low entropy) to disordered ( high order)
What is entropy(S) ?
The measure of disorder and randomness in a system
Reactions are more likely to occur if they
involve large changes in entropy or (-) S
What is Gibb’s Free Energy
Compares the changes in enthalpy and the changes in entropy at a given temperature to predict if a reaction will continue spontaenously or not
Equation for Gibbs Free Energy
ΔG° = ΔH° - TΔS° ΔG° = Gibbs free energy ΔH° = Enthalpy T = Temperature in K ΔS = Entropy
If ΔG° is negative
Exergonic reaction, releases energy , spontaneous , proceeds in the forward direction
If ΔG° is positive
Endergonic reaction , reaction is non spontaneous and proceeds in the reverse reaction
If ΔG° is zero
Equilibrium
