1.7- Redox

Question 1

What are the rules for assigning oxidation numbers

Answer 1

. All uncombined elements have an oxidation number of zero

. The oxidation number of the elements in a compound add up to zero

. The oxidation number of a monoatomic ion is equal to the ionic charge

Question 2

What are the invariable oxidation states for Group 1 and 2 metals, Al, H, F, 3 halogens, and O

Answer 2

.Group 1 metals = +1
. Group 2 metals = 2+
.Al = 3+
. H = +1
. F = -1
. Cl, Br, I = -1, except in compounds with oxygen and flourine
. O = -2 , except in peroxides (H2O2) where it is -1 and also in compounds with flourine

Question 3

What are reducing and oxidising agents

Answer 3

. Reducing agents are electron donors
. Oxidising agents are electron acceptors

Question 4

How do you balance a redox equation

Answer 4

. Work out oxidation numbers for element being oxidised/reduced
. Add electrons equal to the change in oxidation number
. Check to see that the sum of the charges of the reactant side is the same as the charges on the product side

Question 5

How do you balance a more complex half equation that contains a varying amount of O

Answer 5

.First write out the half equation with the ion changing oxidation states
. Balance the charge in O with electrons
. Add H20 in products to balance O’s in MnO4-
. Add H+ in reactants to balance the H’s in H2O
. Check to see that the sum of the charges on the reactant side equals the sum of the charges on the products side

Question 6

How do you combine half equations

Answer 6

You have to make sure the amount of electrons in both of the equations in the same amount, after you have balanced them then you must add the equations with the electrons each being in the opposite side of the equations, then cancel the electrons and other common products