C4 - Acids and Redox Flashcards
What happens when an acid dissolves in water?
It releases hydrogen ions as protons, H+, into the solution.
What is a strong acid?
An acid which completely dissociates and releases all of its hydrogen atoms into a solution as H+ ions and completely ionises.
E.g. HCl
What is a weak acid?
One which partially dissociates and doesn’t release all of its hydrogen atoms as H+ ions. It doesn’t ionise completely.
E.g. CH3COOH
What is a base?
A metal oxide, hydroxide or carbonate
What is an alkali?
A base which dissolves in water, releasing OH- ions into the solution.
What is produced in the reaction of an acid and an alkali?
A salt and water
What is produced in the reaction of an acid and a base?
oxide/hydroxide
A salt and water
What is produced in the reaction of an acid and a carbonate?
A salt, water and carbon dioxide
What is a titration?
A method used to measure the volume of one solution that reacts exactly with another solution, used for finding the concentration of a solution, identification of an unknown chemical or finding the purity of a substance.
What is a standard solution?
How is it prepared?
A solution with a known concentration.
The solid is weighed accurately then dissolved in a beaker using less distilled water than will be needed to fill the volumetric flask.
Transfer the solution into the flask and rinse the final traces into the flask.
Fill the flask to the graduation line so the bottom of the meniscus lines up to the mark.
Invert it several times to mix it thoroughly.
How is the acid-base titration procedure carried out?
Add a measured volume of one solution to a conical flask using a pipette and the other solution in the burette and record the initial reading.
Add a few drops of indicator to the flask solution.
Run the solution in the burette into the flask and swirl the flask until the colour changes to mark the end point.
The titre (volume of solution added) is calculated
A trial is carried out to find the approximate titre.
Repeat to find concordant results.
How are titration calculations carried out?
Work out the amount, in moles, of the solute in the solution for which you known both the concentration and volume.
Use the equation to work out the number of moles of solute in the other solution.
Work out unknown info about the solute in the other solution.
What is the oxidation number?
A measure of the number of electrons that an atom uses to bond with atoms of another element.
It is derived from a set of rules.
What is the oxidation number for elements?
Always zero
What are the oxidation rules for compounds and ions?
Each atom in a compound has an oxidation number
An oxidation number has a sign placed before the number
The sum of oxidation numbers = total charge
The most electronegative element is given their oxidation number first
