Unit 4: Acids and Bases Flashcards
What are some properties of acids?
pH<7
Taste sour
Dissolve metals and form hydrogen gas
Conduct electricity (electrolytes)
What are some properties of bases?
pH>7
Taste bitter
Feel slippery
Conduct electricity (electrolytes)
What does water have to do with acids and bases?
They are only acids and bases when dissolved in water. For example, HCl(solid) is just hydrogen chloride (an ionic compound with no acid properties)
What are some uses of acids?
Some batteries.
Stomach acid.
Fertilizers.
Petroleum production.
What are some uses of bases?
Cleaning products
Soap
Medicine (like antacids)
Water treatment
Cement, mortar, and plaster.
How do you write the dissociation of acids and bases?
On the left, write the acid/base. On the right, write it broken apart into its ions. Remember that dissociation is reversible so double arrows must be used. Remember to write the physical states and charges.
What are the two theories of acids and bases?
The Arrhenius theory of acids and bases.
The Bronstead/Lowry theory of acids and bases.
What is the Arrhenius theory of acids and bases?
Svante Arrhenius discovered that the properties of acids and bases were caused by H+ ions and OH- ions when dissolved in water.
Both acids and bases dissolve in water to form ions. Water is usually not included, although there is evidence to show that H3O+ (hydronium) is produced.
What is the Bronstead/Lowry theory of acids and bases?
The noticed that some bases have not OH- ions.
Acids are compounds that donate a proton.
Bases are compounds that accept a proton.
What are conjugate acids/bases
In the reverse direction by the Bronstead/Lowry theory, acids become bases and bases become acids (conjugates).
What is an amphoteric substance?
A substance that can act as an acid in one reaction and a base in another. Such as HSO4.
What is a polyprotic acid?
An acid that can donate more than one hydrogen ion. The first H+ ion is the easiest to remove. Subsequent H+ ions are more difficult to remove because the compound gains a negative charge.
For example: H3C6H5O7 can lose 3 hydrogen ions. This means it has three dissolving reactions.
What is a strong acid?
An acid that dissolves completely in H2O and produces a high concentration of H+ ions. Strong bases are the same but with OH- ions instead of H+ ions. They are strong electrolytes.
What are weak acids?
They dissolve poorly in H2O and produce a low concentration of H+ ions. Weak bases are the same but with OH- ions instead of H+ ions. They are weak electrolytes.
What are ionization constants?
Because acid/base solutions are systems at equilibrium, we can write an equilibrium expression and solve for the equilibrium constant.
Ka: acid equilibrium constant
Kb: base equilibrium constant
Kw: Water equilibrium constant
Write the equations as normal equilibrium constant equations.
How do you use an ionization constant to determine which side is favoured?
Ka>1: products favoured (strong acid)
Ka<1: reactants favoured (weak acid)
Same for Kb.
Does water ionize?
Yes, but not well. It produces H+ and OH- ions. In pure neutral water, [H+]=1.0x10^-7 and [OH-]=1.0x10^-7.
What is [H+][OH-] in water?
Always 1.0x10^-14
How do you tell how much H+/OH- ions an acid/base will make when dissolved?
If strong, they fully dissolve and correlate directly to their reactants. Ex: if HCl is a strong acid and one mole is dissolved in 1 liter of water, HCl -> 1H+ + 1Cl- : 1 mole of H+ ions is produced
If weak, use the kb/ka and occassionally the kw to find the OH-/H+ ions.
What does pH stand for?
Potenz of the hydrogen ion
What do the pH values indicate?
pH<7: acidic
pH>7: basic
pH=7: neutral
What scale does pH use?
The logarithmic scale. An increase/decrease of 1 pH is 10x the concentration.
What is pOH?
pOH is pH but measuring OH-. pOH+pH is always 14. This can be used to simplify questions.
How do you calculate pH?
Take the negative log of the concentration of H+
pH=-log([H+])
You can reverse this (find [H+] from pH) with [H+]=10^-pH
Conjugate base/acid pairs differ by…
A single proton (hydrogen ion)
What are Ka, Kb, and Kw?
The acid, base, and water equilibrium constants
Difference in meanings between [H+] and Ka? (Or base equivalent)
[H+] > 1.0x10^-7M is acid
= 1.0x10^-7 is neutral
< 1.0x10^-7 is basic
Replace acid with base and base with acid for [OH-].
Ka just refers to the strength of the acid. (Kb refers to strength of base)
For Ka and Kb, how do you tell whether or not something is a strong acid/base?
If kb/ka > 1 : strong base/acid
If kb/ka < 1: weak base/acid
You are given a compound and asked to find its conjugate acid. How is this done?
Add 1 hydrogen and increase the charge by one
Do the opposite for conjugate bases
Rule of 1000
If you divide the initial concentration by the kps and the product is more than 1000, the change is negligible, relative to the concentration and you can omit the change to simplify the equation.
Ex. 0.5M weak acid changes by x. Ka is k. 0.5M/k… if the result is greater than 1000, the change is negligible
What is titration?
When equal moles of a strong acid and strong base are mixed together, they neutralize each other (pH=7) to form water and an ionic compound.
Weak base and strong acid mixed together (equal amounts), what happens?
Slightly acidic. And vice versa.
How can you use titration to determine the concentration of an acid/base?
If one is known, you can calculate the concentration of the unknown. Use CaVa=CbVb
How do you mark the equivalence point in titration?
You use an indicator.
Titration calculation formula
(Ca)(Va)(nb)=(Cb)(Vb)(na) Remember to balance your equations. na and nb are the coefficients of the acids and bases in the balanced reaction.
What should you do before any equation?
Balance! Always balance!
What should you remember about keq equations?
Remember balanced equations when solving, squares and multiples, etc
What should you remember about the rule of 1000?
It is relative. x change alone is relevant. N+-x, x may be negligible.
Initial concentration over ksp
ICE calculations, what should you remember?
BALANCE. Remember double arrows
What are indicators?
Dyes that change colour under varying pH levels
Difference between titration and neutralization
Titration involves a known concentration in neutralization
Neutralization is just that
What is a standard solution?
A solution with known concentration
What is the equivalence point
The point at which the solution is neutral
