Which of the following are redox reactions? For those that are, indicate which element is oxidized and whisch is reduced. For those that are not, indicate whether they are precipitation or neutralization reactions.
(a) P4(s) + 10HClO(aq) + 6H2O = 4H3PO4(aq) + 10HCl(aq)
(b) Br2(l) + 2K(s) = 2KBr(s)
(c) CH3CH2OH(l) + 3O2(g) = 3H2O(l) + 2CO2(g)
(d) ZnCl2(aq) + 2NaOH(aq) = Zn(OH)2(s) + 2NaCl(aq)
a,b,c
A,B,C
I'm lost on the entire part. I did not understand this part of the chapter at all and I'm using this problem out of the book to study for the test.
(a) This is a redox reaction. Phosphorus (P) is oxidized from an oxidation state of 0 in P4 to +5 in H3PO4, and chlorine (Cl) is reduced from +7 in ClO to -1 in HCl.
(b) This is a redox reaction. Bromine (Br) is reduced from 0 in Br2 to -1 in KBr, and potassium (K) is oxidized from 0 to +1.
(c) This is a redox reaction. Carbon (C) in ethanol is oxidized from -2 in CH3CH2OH to +4 in CO2, and oxygen (O) is reduced from 0 to -2 in H2O.
(d) This is not a redox reaction. It is a precipitation reaction. Zinc (Zn) is still in the +2 oxidation state before and after the reaction, and chlorine (Cl) is also in the -1 oxidation state before and after the reaction. The reaction can be represented as: ZnCl2(aq) + 2NaOH(aq) → Zn(OH)2(s) + 2NaCl(aq).
To determine if a reaction is a redox reaction, you need to compare the oxidation states of the elements in the reactants and products. If there is a change in the oxidation state of an element, it indicates a redox reaction.
Let's analyze each reaction:
(a) P4(s) + 10HClO(aq) + 6H2O = 4H3PO4(aq) + 10HCl(aq)
In this reaction, the oxidation state of phosphorus (P) changes from 0 in P4(s) to +5 in H3PO4(aq). This indicates that phosphorus is oxidized. The oxidation state of chlorine (Cl) changes from +1 in HClO(aq) to -1 in HCl(aq), indicating that chlorine is reduced.
So, reaction (a) is a redox reaction, and phosphorus is oxidized while chlorine is reduced.
(b) Br2(l) + 2K(s) = 2KBr(s)
In this reaction, the oxidation state of bromine (Br) in Br2(l) remains 0, and the oxidation state of potassium (K) in 2K(s) also remains 0. Therefore, there is no change in the oxidation states, indicating that it is not a redox reaction.
So, reaction (b) is not a redox reaction.
(c) CH3CH2OH(l) + 3O2(g) = 3H2O(l) + 2CO2(g)
In this reaction, the oxidation state of carbon (C) in CH3CH2OH(l) changes from -2 to +4 in CO2(g), indicating that carbon is oxidized. The oxidation state of oxygen (O) changes from 0 in O2(g) to -2 in H2O(l) and +4 in CO2(g), indicating that oxygen is both reduced and oxidized.
So, reaction (c) is a redox reaction, and carbon is oxidized while oxygen is both reduced and oxidized.
(d) ZnCl2(aq) + 2NaOH(aq) = Zn(OH)2(s) + 2NaCl(aq)
In this reaction, the oxidation state of zinc (Zn) in ZnCl2(aq) remains +2, and the oxidation state of oxygen (O) in NaOH(aq) remains -2. Therefore, there is no change in the oxidation states, indicating that it is not a redox reaction.
So, reaction (d) is not a redox reaction.
To summarize:
(a) Redox reaction: Phosphorus is oxidized, and chlorine is reduced.
(b) Not a redox reaction.
(c) Redox reaction: Carbon is oxidized, and oxygen is both reduced and oxidized.
(d) Not a redox reaction.
a,c
I could write a book (well, maybe only a short one) about this. Exactly where are you having trouble.
1. You need to know how to determine the oxidation states of each element. I can give you a link for that.
2. You need to know which are oxidized and which reduced. Remember this definition. Oxidation is the loss of electrons.
3. For pptn reactions you need to know solubilities. I can give you a link for that.