Acids And Bases Flashcards
What are buffers used for
Preventing large pH changes
What are good buffers
Solutions of weak acid or base and it’s conjugate
Describe the common ion effect
A weak electrolyte will ionize less if you add a strong electrolyte that has an ion in common with the weak electrolyte
What happens when you add OH to a solution of HF?
What happens if you add H?
The OH reacts with H to make water. The concentration of H decreases and there will be more F
The H will react with F and produce more HF reducing the F- concentration
Which are good buffers? @-HF and NaF B-NH3 and NH4Cl C-KOH and KF D-CH3COOH and LiCH3COO- E-NaNO3 and HNO3 F-NaOH and NaCl G-HCl and Na CH3COO-
A,B,D
Within what range do buffers work?
pH=pKa +/-1
Acid base ratio less than 1:10 or 10:1
Acid and base amount of optimum buffers?
[HA]=[A]
How do make a buffer using table of Ka
Exponent close to pH and equal concentration of acid and base
How to find pH of a buffer after adding a substance that changes pH?
Use henderson hasselbach
What happens to SA of SB added to a buffer?
All SA or SB are consumed in the reaction
Steps for recalculating pH after strong acid or base
Stochiometry 1. Add sB or SA 2. Neutralize 3.. Recalculate [Hx] and [X-] Equilibrium Use Kw, [Hx] and [X-] to calculate [H+] Find pH
Alternative hasselbach
Ka=[H3O+] ([A-][HA])
How does the PH change when a base is added
Slightly
When is pH equal to pKa
When n of acid =moles of base
What is the endpoint of a titration
Indicator changes color
Equivalence point
n of acid =n of base
Titration is correct when
Endpoint and equivalence point reached at the same time
Describe the tritration curve of a SA with a SB
Starts low on pH scale.
Slow to reach equivalence point
Equivalence point at 7
Just before and after the equivalence point the pH rapidly increases
What is at the equivalence point of a SA+SB
Water + salt of cation of Base and anion of acid
Titration of WA+SB
-cB affects pH
pH at equivalence point is>7
-pH changes near equivalence point are more subtle
When can you estimate salt solubility from KSP?
When salts have same ion:ion ratio
Does solubility change with temperature?
Yes
How does the common ion effect change solubility
If there are already ions of the salt in solution the solubility od the salt will decrease
In what kind of solution do acids dissolve?
Basic
When will a precipitate form?
When a solution bis super saturated Q>Ksp
When is a solution unsaturated
Q
When is the solubility of a system at equilibrium?
Q=Ksp
When do metal ions affect solubility
When they act as lewis acids and react with complex ions that act as lewis bases
When metal oxides and hydroxides can act as acids or bases?
When dissolved in strong acid or base
Describe gravimetric analysis
Separating a precipitate from a solution by filtration
Differences in salts can separate ions in a mixture
True
When is a reaction neutralized
When moles of acid =moles of base
Volumetric analysis
Find how much substance there is using a titration
Titrant
Substance delivered from buret (we know it’s volume)
Analyte
Substance that is analyzed (volume must be known)
