Chapter 4 - Acids and redox Flashcards
What is a Bronsted- Lowry Acids
They are defined to be proton donors.
What is a Bronsted-Lowry Base
They are defined to the proton acceptors
Give 3 examples of strong acids
Sulfuric acid (H2SO4) Hydrochloric acid (HCl) Nitric acid (HNO3) Because they are all inorganic acids (or minerals)
Give an example of a weak acid
Ethanoic acid (CH3COOH) Just carboxylic acids in general because they are organic acids.
What is the difference between an alkali and a base
An alkali is any soluble base.
3 examples of strong alkalis
NaOH
KOH
Ca(OH)2
1 example of a weak acid
NH4OH
acid + alkali –>
salt and water
acid + carbonate –>
salt + water + carbon dioxide
Ionic equation for neutralisation
H+(aq) + OH-(aq) –> H20 (l)
Explain sulfuric acid’s strength
It has 2 hydrogen atoms, but it is only strong for one of them. So it fully dissociates with 1, and then partially dissociates in the other.
H2SO4(aq) –> H+(aq) + HSO4-(aq)
HSO4-(aq) H+(aq) + SO4 2- (aq)
ionic equation for acid and oxides
2H+ + O2- –> H20
ionic equation for acid and carbonates
2H+ + CO3 2- –> H2O + CO2
ionic equation for when water mixes with hydrogen
H+(aq) + H2O(l) –> H3O+(aq)
This happens by a dative covalent bond because the oxygen had 2 lone pairs, one of which it now shares with this third hydrogen.
The new compound is called hydroxonium.
What is titration
A technique used to accurately measure the volume of an unknown solution that reacts exactly with another known solution.
What can titrations be used for
finding the concentration of a solution
identification of unknown chemicals
finding the purity of a substance
Explain diprotic molecule
It is a molecule that has 2 hydrogens. Immediately, this is the stronger acid because it has more hydrogen ions to release and carry the charge.
As a solution is diluted, what happens to its current flow
If a solution is diluted, the concentration of H+ ions decreases. If there is less ions to carry the charge, the electrical conductivity will decrease.
Why does a stronger acid have a higher electrical conductivity?
A stronger acid can ionise fully and release more ions per unit of volume of solution to carry the charge through the electrolyte.
Rule for halogens
They are usually -1.
But they are positive with oxygen and fluorine
Rule for hydrogen with metals
-1 oxidation number
Rule for hydrogen with non- metals
+1 oxidation number
Rule for oxygen
Usually -2
But -1 is peroxide (H2O2)
Rule for fluorine
Always -1
How to calculate percentage uncertainty
uncertainty/ capacity * 100%
What is the % uncertainty on a 100cm3 volumetric flask
+- 0.20cm3
What is the % uncertainty on a 250cm3 volumetric flask
+- 0.30cm3
Effect on titre if the pipette has an air bubble
creates a smaller titre because there is actually less volume
Effect on the titre if the burette reading are taken from the top, rather than the bottom of the meniscus
Wouldn’t be affected because the change in volume would still be the same.
when do you multiply the number by 2 when calculating the % uncertainty
if you have used that object twice
Uncertainty of a 10cm3 pipette
+- 0.04 cm3
Uncertainty of a 25cm3 pipette
+- 0.06cm3
Uncertainty of a 50cm3 pipette
+- 0.10cm3 (0.05 * 2 because its read twice)
oxidation numbers:
reduction
decrease in oxidation number
oxidation numbers:
oxidation
increase in oxidation numbers
H in metal hydrides
-1
O in peroxide (H2O2)
-1
O is bonded to F
+2
nitrite
no2 +3
nitrate
no3 +5
