CHAPTER 4: ACIDS AND REDOX Flashcards
What are acids?
Proton donors that release H+ ions in aqueous solution.
What are alkalis?
Proton acceptors that release OH– ions in aqueous solution.
What are common acids?
- Hydrochloric acid, HCl
- Sulphuric acid, H2SO4
- Nitric acid, HNO3
- Ethanoic acid, CH3COOH
What are common alkalis?
- Sodium hydroxide, NaOH
- Potassium hydroxide, KOH
- Ammonia, NH3
What is a strong acid?
Strong acids fully dissociate, and protons are easily lost.
What is a weak acid?
Weak acids only partially dissociate, and protons are not easily lost.
What is a strong base?
Strong bases fully dissociate, and hydroxide ions are easily lost.
What is a weak base?
Weak bases only partially dissociate, and hydroxide ions are not easily lost.
What is the method for titration?
- A measured volume of x is added to a conical flask using a pipette, along with a suitable indicator to the flask, e.g. phenolphthalein, methyl orange
- The burette is filled with the other solution, y, which is of a known concentration
- A small quantity of y flows into the flask with x. This is allowed to occur until the end point is reached, indicated by a colour change
- The volume of y that has been added is measured and unknowns can then be calculated
What is a standard solution?
Standard solutions are solutions of a known concentration.
What is the method for a standard solution?
- A known mass of the solute is dissolved in
a chosen solvent in a beaker - The solution is transferred into a volumetric flask. Several washings are also made and transferred to the volumetric flask
- More solvent is added to the volumetric flask until the level is nearly at the graduation line
- The solvent is then added drop by drop until the bottom of the meniscus is sitting on the graduation line. Do not allow the solution to fill above the line
- The volumetric flask is sealed and the solution mixed thoroughly by inverting it multiple times
What is neutralisation?
acid + base ➡️ salt + water
H+ +OH- ➡️ H2O
What are salts?
Salts are ionic compounds in which the H+ ion of an acid has been replaced by a metal ion or another positive ion. Salts are made up of a cation — the positive ion, usually a metal ion or ammonium ion and an anion — the negative ion, usually derived from an acid.
What an acid and an alkali make?
acid + base ➡️ salt + water
What does an acid and a metal make?
acid + metal ➡️ salt + hydrogen (gas)
What does a metal oxide and an acid make?
acid + metal oxide ➡️ salt + water
What does an acid and a metal carbonate make?
acid + metal ➡️ salt + water + carbon dioxide
What is oxidation and reduction?
Oxidation is gain of electrons and reduction is loss of electrons.
What is an oxidation number?
A number representing the number of electrons that an atom uses to bond with atoms of another element.
What are the rules of oxidation?
- An element has an oxidation number of 0
- A simple ion (of a single element) has an oxidation number equal to the charge on the ion
- The sum of oxidation numbers of the elements in a compound is equal to the overall charge of the compound
- The charge on a complex ion, e.g. NH4+, is equal to the sum of the oxidation numbers
- The most electronegative element in a compound always has a negative oxidation number
What is an oxidising agent?
• Cause oxidation of other species,
and so are themselves reduced
• Reduction is the gain of
electrons — oxidising agents gain electrons
What is a reducing agent?
• Cause reduction of other species,
and so are themselves oxidised
• Oxidation is the loss of electrons — reducing agents donate electrons
