Module 2 Reactions And Calcualtions Flashcards
What is the oxidation number
Value given to an element in a chemical species which represents number of electrons lost/gained
How is the oxidation number written
-2 not 2-, that’s charge
What do the Roman numerals show
Oxidation state of transition metals and other elements
What are the first 8 Roman numerals
1=l 2=ll 3=lll 4=lv 5=v 6=vl 7=vll 8=vlll
What is the oxidation number of c in CO
O is -2 due to rule 6 so to cancel out +2
What is the oxidation number of S in S2O3^2-
(-2)3=-6-2=-4 so opposite which is +4 then half as it goes from s2 and you want s, so +2
What is the name of SnO2
(-2)2=-4 so Tin (lv) oxide
What is the name of FeCl3
(-1)3=-3 so iron (lll) chloride
What are the 7 rules for assigning oxidation numbers
- Oxidation number of a neutral element is O eg Na=O 2. Oxidation of a monoatomic ion is same as charge eg Na+=+1 3. In compounds, group 1 is +1, group 2 is +2, group 3 is +3. 4. Hydrogen in a compound, usually +2 except hydrides eg NaH. 5. Fluorine always -1 in compounds. 6. Oxygen in compounds usually -2 except peroxides eg H2O2. 7. Cl, Br,I usually -1 except ocl2 and NaclO3. 8. Sum of all oxidation numbers in a neutral compound=0. 9. Sum of all oxidation numbers in a poly atomic ion=charge
What is water of recrystallisation
Some solid ionic compounds have trapped water in then when they are formed from their aqueous solutions.
What is a hydrated salt
A solid salt containing water of crystallisation
What is a anhydrous salt
Doesn’t contain water of crystallisation
What is the oxidation state of P in P4
0
Give range of oxidation state of phosphorus
+5 to -3
Define half equation
Shows 1 element/ion and movement of electrons
What does OILRIG stand for
Oxidation is loss of electrons/gain of oxygen and reduction is gain of electrons/loss of oxygen
Define oxidising agent
Species that causes another species to be oxidised (reduced itself)
Define reducing agent
Species that causes another species to be reduced (oxidised itself)
What does an increase in oxidation number mean
Oxidised
What does a decrease in oxidation number mean
Reduced
Define a disproportionation reaction
One element has been both oxidised and reduced in a reaction
What steps do you follow to make a half equation
Balance number of atoms on each side, work out charge on each side, add e- to more positive side to balance charge
What is a redox equation
When oxidation and reduction happen at the same time in a reaction
