2.4 Acids and Redox Flashcards
What do all acids contain ?
Contain H+ ions, which are released when dissolved.
What do all alkali’s contain ?
Contain OH- ions, which are released when dissolved.
What is a strong acid ?
Fully dissociates all of the H+ ions in a solution. E.g. Hydrochloric acid (HCl)
What is a weak acid ?
Partially dissociates, so only releases a few H+ ions in. solution. E.g. Ethnic acid (CH3COOH)
What does a metal base produce when reacting with an acid ?
Metal + acid = salt + hydrogen
What does a metal oxide/hydroxide produce when reacting with an acid ?
Metal oxide/hydroxide + acid = salt + water
What does a metal carbonate produce when reacting with an acid ?
Metal carbonate + acid = salt + water + carbon dioxide
What does an alkali produce when reacting with an acid ?
Alkali +acid = salt + water
What is a neutralisation reaction ?
When an acid and a base react to form a salt and water. The H+ ions are replaced with metal or ammonium ions.
Example of neutralisation reaction
HCl + NaOH = NaCl + H20
Ionic equation for neutralisation reaction
H+ + OH- = H20
What is oxidation ?
Oxidation is the loss of electrons /gain on oxygen.
What is reduction ?
Reduction is gain of electrons / loss of oxygen.
Oxidation number rule 1: in terms of atoms
An atom in an element has an oxidation number of 0. (Na = 0)
Oxidation number rule 2: in terms of simple ions.
In all simple ions, the oxidation number is always the charge of the ion. (Cl- = -1)
Oxidation number rule 3: in terms of compounds
In a compound, the sum of the oxidation numbers is 0. (MgO=0)
Oxidation number rule 4: in terms of fluorine
Fluorine in a compound has an oxidation number of -1. (KF= -1)
Oxidation number rule 5: in terms of hydrogen
Hydrogen in a compound has an oxidation number of +1 unless it is in a metal hydride, where it is -1.
Oxidation number rule 6: in terms of oxygen
Oxygen in a compound has an oxidation number of -2, unless it is bonded to fluorine or in a peroxide. (F20, H2O2)
Oxidation number rule 7: in terms of charge of ions in a compound
The sum of the oxidation numbers in a compound ion equals the charge of the ion. (CO3 2- = -2)
Oxidation number rule: roman numerals
Roman numerals indicate the oxidation number of the element but no sign is displayed. (Cu (II)SO4)
How to work out percentage error ?
Error/ Amount x 100
Need to multiply by 2 is there is two measurements.
What is a redox reaction ?
Redox reactions involve reduction and oxidation together. If one happens so does the other.
What is a titration reaction used for ?
Used to measure volume of one solution that reacts with exactly with another solution. Used to find the concentration of a solution, identify unknown chemicals and find the purity of a substance.
What is a standard solution ?
Standard solution is a solution of a known concentration. A volumetric flask is used to make a standard solution accurately.
How to calculate mean titre ?
Only use concordant results (0.1 difference). This keeps the mean accurate to the titration.
How to calculate titration ?
1) Find amount, in mol, of solute. (c x v =n)
2) Use equation to find mol of other solute of solution using empirical formula.
3) Work out unknown information about solutes in other solution.
What are some disadvantages of the upward delivery tube ?
-Cant measure volume of gas.
-Gas can escape as air is displaced out of bottom of delivery tube.
-Gas must be less dense than air so floats to top of delivery tube.
What are some disadvantages of the downward delivery tube ?
-Cant measure volume of gas.
-Gas can escape as it is an upward displacement of air.
-Gas must be denser than air so it stays in the tube.
How does the displacement of water gas collecting method work ?
Gas fills the tube and pushes (displaces) water out of the tube. You can measure the volume of gas through displacement of water.
What is a disadvantage of the displacement of water method ?
Can only work for collecting gases that are insoluble in water.
How does the gas syringe collecting method work ?
Allows you to measure volume of gas as it pushes syringe outward due to pressure build up in apparatus. The syringe move to keep pressure the same throughout.
What is an advantage for the gas syringe method ?
All gases can be collected using the syringe method.
What is a disproportionation reaction ?
When an element is both oxidised and reduced in the same reaction.
What happens to the oxidation number if an element has been oxidised ?
The oxidation number goes up if an element has been oxidised as it has lost electrons.
What happens to oxidation number if an element has been reduced ?
The oxidation number goes down if the element has been reduced as it has gained electrons.
