Answer:
Step-by-step explanation:
1)The oxidation state of an element in elemental form is zero. * True*
Hint: The oxidation state of an element in its elemental form is zero, The charging present on an ion is same as the oxidation number of the ion, for instance an ion may have oxidation number of +3 or a -3 oxidation number therefore, the statement is true
2)Oxygen must be present in order for oxidation to occur. * False*
Hint: Oxidation can also be loss of electron by a substance. therefore, it's not a must for oxgen to be present for oxidation to take place,
3)When an atom gains electrons its charge decreases. * True*
Hints: whenever there is a an equal number of protons and electrons, by an atom its net charge become zero 0. Then If it gains an electron, it becomes negatively charged i.e an anion. However, If it loses an electron, itbecomes positively charged i.e cation.
4)Redox reactions include combustion reactions and decomposition reactions
Hint: There are 5 main types of redox reactions, which are
combination, disproportion reaction decomposition and displacement, combustion
5)Nickel metal can replace or "push out" cobalt in a reaction according to the Activity of metals listing
Hints: on the reactivjty series of metal chart Cobalt comes before Nickel, and a more reactive metal will only displace a less reactive metal from a compound.
6)
The rusting or corrosion of iron can be represented by 4Fe + 3O2 --> 2Fe2O3. Which atom is reduced?
Fe Oxygen itself need not be involved in an oxidation reaction. * True
Hint Oxygen is reduced, iron is oxidized
7)
In a reduction half reaction electrons are a reactant. * True*
Hints: in all reduction half-reactions we have electrons always appear as reactants on the left side.