Unit 5- Acid- Base Equilibria Flashcards
What are the PH ranges for acidic, neutral, and basic (alkaline) solutions?
- Acidic: 0-6.9
- Neutral: 7.0
- Basic: 7.1- 14.0
What were acids and bases traditionally thought of?
- Acids: Anything that was sour (ex. lemons contain citric acid, vinegar is diluted acetic acid)
- Bases: Bitter taste and slippery feel (ex. soap)
Explain the traditional/ Arrhenius Theory
- The properties of acids were due to the presence of hydrogen ions, H+. Thus, acids were defined as compounds that produce H+ ions in aqueous solution.
- The properties of bases were due to the presence of hydroxide ions. OH-. Thus, bases were defined as compounds that produce OH- ions in aqueous solution.
- The theory explained a lot of acid-base chemistry but was limiting because it only describes one type of base - those containing the hydroxide ion.
What does it mean for a compound to be polyprotic?
The compound has the ability to donate more than 1 proton (H+)
Explain the Bronsted-Lowry Theory
- Is said to be the better explanation of acid-base chemistry. It applies to Arrhenius acids and bases plus others.
- An acid is a proton donor
- A base is a proton acceptor
What is an amphiprotic substance?
Substances that can be classified as a Bronsted Lowry acid or base depending on the reaction. Ex) The bisulfate ion, HSO4-, Water
Explain Strong/ Weak Acids and Bases
-Strong acids produce many H+ ions (or H30+ ions): weak acids produce few H+ ions. The stronger the acid, the more H+ ions are produced.
-Strong bases produce many OH- ions: weak bases produce few OH- ions. The stronger the base, the more OH ions are produced.
- Strong acids and bases are essentially one way reactions- The acid or base breaks down completely to produce ions.
- Weak acids and bases, however, do not ionize completely. For weak electrolytes, equilibrium lies to the left side of the equation (the reactant side). The double arrow is commonly used to indicate the partial ionization of the solution.
Explain what different values of Ka and Kb can mean.
- A large value of Ka means there are many H+ ions in solution- in other words, a strong acid. There are many products.
- A large Kb value indicates many OH- ions- a strong base. There are many products
Explain the Key points about Kw
- We usually do not think of water as dissociating/ ionizing, but it does, just not very well
- As long as temperature remains constant, Kw does not change
- A small Kw value means that very few ions are present and most of the water remains “intact” as H20, and few ions form
What does PH stand for?
The potential of hydrogen, that is, the concentration of hydrogen ions in solution.
Explain the PH scale.
Ranges from 0-14 to represent how acidic or basic a solution is
- Acids have a PH <7
- The lower the PH, the stronger the acid
- A neutral solution has a PH of 7
- Bases have a PH >7
- The higher the PH, the stronger the base
The scale is logarithmic meaning that every change of one unit on the scale represents a 10-fold change in concentration (10^1)
What is titration?
Titration is a process where a known property of one solution is used to infer an unknown property of another solution
What is acid-base Titration?
- In an acid-base titration, the sample in the receiving flask may be an acid or a base. If the sample is the base , the titrant is an acid (or vice versa). ( This applies most of the time)
- The goal of the acid-base titration is to add enough acid to neutralize the base (or vice versa)
What is neutralization?
- A special type of double displacement reaction
- strong acid + strong base > water (l) + salt
- After the reaction, the salt solution is neutral, meaning it contains equal moles of H+ and OH- ions
What is the equivalence point?
- The point in which the acid and base are mixed in exactly the right proportions to neutralize each other is known as the equivalence point
- The equivalence point occurs when the number of moles of base is neutralized by equal number of moles of acid
