Chapter 8 Test Flashcards
(22 cards)
What is the Arrhenius Definition of Acids and Bases?
Acids are compounds that produce H+ ions in water
Bases are compounds that produce OH- ions in water
They are electrolytes
Why is the Arrhenius Theory limited?
Not all bases have OH- in their formulas, and not all acid-base reactions take place in water.
What is the Bronsted Lowry Definition of Acids and Bases?
Acids donate H+
Bases accept H+
Why is hydronium formed when an acid is placed in water? What is water in this situation?
Hydronium is formed because H+ is not stable on its own.
In this case, water is a bronsted lowry base since it accepts H+ from an acid
What is a conjugate acid-base pair?
A pair of substances whose molecular formulas differ by a H+ ion.
An acid donating an H+ will become a conjugate base, and a base receiving an H+ will become a conjugate acid.
What is an amphoteric compound?
Compounds that can react both as a base and an acid.
What does the pH measure?
Amount of H+ ions (acidity_ in a solution,
pH < 7 is acidic (more H+ than OH-)
pH > 7 is basic (more OH- than H+)
pH = 7 is neutral
How to determine the concentration when given pH?
[H+] = 10^-pH
What is a strong acid or base?
Compound that ionizes completely in water to form ions, meaning the % ionization is greater than 99%.
What is the acid/base ionization constant?
Measures the extent to which acid donates H+.
A large Ka indicates that product formation is significant, therefore strong acid
A small Ka indicates that product formation is insignificant, therefore weak acid
What is a weak acid or base?
Compound that does not dissociate fully into ions / does not release all OH-/H+ ions in water
These are reversible reactions, equilibrium stays on reactant side, resulting in a small Ka/b
What is the autoionization of water? What can we assume from this?
When two water molecules react, they produce H3O+ and OH-.
From this we may assume that Ka x Kb = 1 x 10^-14
What are acidic/basic/neutral salts?
A compound with 2 different ions that when dissolved in water increases the concentration of H+/OH-
a neutral salt produces neither H+/OH- ions.
How do you know whether a salt is acidic/basic/neutral
Whether it can go back to its weak acid/base when dissolved in water. An ion belonging to a strong acid/base cannot go back. However, if the ion belongs to a weak acid/base, it will go back and produce H3O/OH
What is a titration?
Quantitative analysis method used to determine the concentration of an unknown solution by reacting it with another substance of a known concentration.
How do we know when the titration is done?
When the equivalence point is reached: moles of H+ = moles of OH-
seen through adding an indicator.
What is the titration curve?
when the pH rises gradually, until the midpoint where there is a sharp increase of pH at around pH = 7. the curve then bends to reflect a more gradual increase in pH.
How does the titration curve adjust when weak acids/bases are in the titration?
equivalence point adjusts below or above pH 7, meaning the curve will change when it will have the sharp increase.
What is an acid-base indicator? What is their role?
(HIn) Weak acids that exhibit one colour in their acid form(Hin), and a different colour in their conjugate base form (In-)
Their role is to provide a visible marker of the equivalence point during a titration.
How do you choose an acid-base indicator for a titration?
The indicator chosen must have the end point and the equivalence point as close together as possible- The equivalence point must be where the indicator starts changing colour.
What is a buffer? What is its purpose?
A solution containing a weak acid and its conjugate weak base in approximately equal concentrations.
Its purpose is to resist both acid and base stresses equally well (due to reversibility! and buffering region)
Significance of buffers?
Maintaining pH balance by tolerating addition of acid or bases- crucial for survival of living things!!
