Redox 1 Flashcards
What is an oxidation number?
The number of electrons an atom uses to bond with any other atom
What is the oxidation number of an uncombined element such as C, H, O2?
0
What is the oxidation number of combined oxygen such as in H2O?
-2
Oxidation number of oxygen in peroxides
-1
What is the oxidation number of combined hydrogen such as in NH3, H2S
+1
What is the oxidation number of combined hydrogen such as in metal hydrides, LiH
-1
Oxidation number of a simple ion
Charge on the ion.
Na=+1
Cl=-1
What is the oxidation numberNof combined fluorine such as in NaF, CaF2
-1
When an element has more than one stable oxidation number how is it indicated?
Written as a roman numeral
What is the oxidation number of Fe in iron (Ill) chloride?
+3
What are oxyanions
Negative ions that have an element along with oxygen
Oxidation number of S in SO4 2-
+6
Because, combined oxygen has an oxidation number of -2.
4 X-2 =-8.
The charge on the compound is -2. Sum of oxidation numbers must
equal -2
SO, -2-(-8) = +6
Define oxidation in terms of electron transfer and oxidation number
Oxidation is
- loss of electrons
- increase in oxidation number
Define reduction in terms of electron transfer and oxidation number
Reduction is
-gain of electrons
- decreased oxidation number
What is a redox reaction
A reaction where both oxidation and reduction take place
Oxidation number of a metal
0 because it is an element
What is an oxidising agent
Species that gains electrons
What is a reducing agent
Species that loses electrons
Oxidation state of chlorine in NaClO
+1
Define disproportionation
same species undergoes oxidation and reduction simultaneously
Ocidation state of P in PCl5
+5
Oxidation state of nitrogen in ammonia
+3
Oxidation state of arsenic in AsO4 3-
+5
Oxidation state of iron in K4Fe(Cn)6
2+
6 type of ionic equations
Dissociation into ions
Displacement reactions
Redox
Metal reacts with acid
Neutralisation
Precipitation
What is dissociation
Particles in a substance spread out when heated or dissolved
Ionic compounds are always ….. but ……. In water
Solid
Dissolve
Ionic equation for barium chloride dissociation into ions
BaCl2(aq)+aq—> Ba2+(aq) + 2Cl-(aq)
Ionic equation of magnesium and copper sulfate displacement reaction
Mg(s) + CuSO4(aq)—> MgSO4 (aq) + Cu(s)
Mg(s) + Cu2+(aq)—> Mg2+ + Cu(s)
Ionic equation of sodium chloride and silver nitrite redox reaction
NaCl(aq) + AgNO3(aq)—> NaNO3 (aq) + AgCl(s)
Cl- + Ag+ —> AgCl(s)
Ionic equation of magnesium and sulfuric acid metal reacts with acid
Mg(s) + 2H+ —> Mg2+(aq) + H2(g)
Ionic equation sodium hydroxide and sulfuric acid neutralisation
2OH-(aq) + 2H+ —> 2H2O(l)
Ionic equation of lead nitrate and potassium iodide precipitation reaction
Pb2+(aq) + 2I- —> PbI2(s)
Oxidation agent
Species that accepts electrons, undergoes reduction
Reducing agent
Gives away electrons, undergoes oxidation
Oxidation number rules
Uncombined elements=0
Ions made of just one atom = charge on the ion
Sum of all oxidation states in a compound= 0
Sum of oxidation states of a complex ion = charge on ion
Acids we must know
HCl hydrochloric acid
H2SO4 sulfuric acid
HNO3 nitric acid
Alkalis we must know
NaOH
KOH
Ca(OH)2
What is disproportionation reaction
Same species is oxidised and reduced at the same time
Oxidation state of iron in Fe2O3
+3
Oxidation state of chromium in Cr2O7 2-
+6
Balance this redox reaction
H2SO4–>H2S
H2SO4 + 8e- + 8H+ —>H2S + 4H20
Balance this redox reaction
NO3 - —> NO2
NO3- + 2H+ +e- —> NO2 + H2O
