
What is a half-reaction? Why must the number of electrons lost in the oxidation half-reaction equal the number of electrons gained in the reduction half-reaction? Summarize briefly the steps in the half-reaction method for balancing redox reactions. What two items must be

Interpretation:
The definition for half reaction and balancing of a redox reaction using half-reaction method is to be stated.
Concept introduction:
A redox reaction consists of two parts, one is oxidation and the other is reduction. These two reactions are called half reactions and they are involved in the change of oxidation number of the atoms present in the reaction.
To determine: The definition for half reaction and the steps involved in the balancing of a redox reaction using the half-reaction method; the reason behind the loss and gain of equal number of electrons in the oxidation and reduction half-reaction respectively; the steps involved in the half-reaction method for balancing the redox reaction and the two items that must be balanced in a redox reaction (or any chemical reaction).
Answer to Problem 1RQ
A half reaction is that type of reaction that involves either oxidation or reduction of a redox reaction.
It occurs because of the change in the oxidation number of the atoms involved in the reaction.
The number of electrons lost in the oxidation half-reaction must be equal to the number of electrons gained in the reduction half-reaction, to balance the charge of the overall reaction.
The number of electrons and atoms must be balanced in a redox reaction (or any reaction)
Explanation of Solution
The half reaction consists of either oxidation half or reduction half of a redox reaction.
The reaction in which transfer of electrons occur from one species to another is called redox reaction. The species which lose electron is said to be oxidized while the species which gain electron is reduced.
So, a redox reaction consists of two reactions, one is the oxidation half and the other is reduction half.
A half reaction can be either oxidation one or reduction one and it occurs because of the change on the oxidation number (state) of the species involved in the reaction.
The number of electrons lost during oxidation and those gained during reduction must be equal to maintain the overall charge of the redox reaction.
The equal gain and loss of electrons can be explained as follows,
Cu(s)→Cu2+(aq)+2e- (1)
2Ag+(aq)+2e-→2Ag(s) (2)
Adding the above two equations
Cu(s)+2Ag+(aq)→Cu2+(aq)+2Ag(s) (3)
To balance the overall charge and mass, the equation (2) is multiplied by 2 that gives the final equation (3) that satisfies both the required conditions.
The steps involved in the balancing of redox reaction by half-reaction method can be summarized as follows.
In acidic medium, the reaction of reaction of Fe(II) with potassium permanganate is,
FeSO4+KMnO4+5H2SO4→Fe2(SO4)3+MnSO4+H2O+K2SO4 (4)
The ionic reaction can be represented as,
Fe2++MnO-4+H+→Fe3++Mn2++H2O (5)
- The oxidation half and reduction half of the reaction, respectively, is,
Fe2+→Fe3+ (6)
MnO-4→Mn2+ (7)
- Balance the oxidation half-reaction by the addition of one electron to the right hand side of the reaction.
Fe2+→Fe3++e- (8)
- Balance the reduction half-reaction. As the oxygen atoms are not balanced, try to balance them by adding equal number of water molecules on the opposite side.
MnO-4→Mn2++4H2O (9)
- Balance the hydrogen atoms by adding equal number of H+ on the opposite side.
MnO−4+8H+→Mn2++4H2O (10)
- The charge on Mn at left side is +7 while on right side is +5 Balance the charge on both sides by adding 5 electrons on the left hand side.
MnO-4+8H++5e-→Mn2++4H2O (11)
- To balance the overall charge, multiply equation (8) by 5.
5Fe2+→5Fe3++5e- (12)
- Add equation (11) and (12).
MnO-4+8H++5Fe2++5e-→Mn2++4H2O+5Fe3++5e- (13)
- To write the final equation, cancel out the electrons on both the sides.
MnO-4+8H++5Fe2+→Mn2++4H2O+5Fe3+ (14)
The number of atoms and electrons must be balanced in a redox reaction (or any chemical reaction).
According to the law of conservation of mass, mass can neither be created nor destroyed in a chemical reaction. Therefore mass of every species must be conserved in the reaction. Therefore to balance mass, the number of atoms must be balanced in a chemical equation. Besides this the charge on both the sides of the reaction must be balanced to maintain the overall charge of the reaction.
The redox reaction consists of the reduction half-reaction and oxidation half-reaction. The reaction must be properly balanced to maintain the law of conservation of mass and overall charge
Want to see more full solutions like this?
Chapter 18 Solutions
Chemistry
- Fina x | Sign X Sign X lab: X Intro X Cop) X a chat x My x Grad xLaur x Laur x a sheg X S Shoj XS SHE X acmillanlearning.com/ihub/assessment/f188d950-dd73-11e0-9572-0800200c9a66/d591b3f2-d5f7-4983-843c-0d00c1c0340b/f2b47861-07c4-4d1b-a1ee-e7db27d6b4ee?actualCourseld=d591b3f2- 5 © Macmillan Learning Organic Chemistry Maxwell presented by Macmillan Learning For the dehydrohalogenation (E2) reaction shown, draw the Zaitsev product, showing the stereochemistry clearly. H H KOH Br EtOH Heat Select Draw Templates More Erase // C H Q Search hp Q2 Q Δ קו Resouarrow_forwardIs the structural form shown possible given the pKa constraints of the side chains?arrow_forwardon x Fina X Sign X Sign x lab X Intro X Cop X chat X My x Grac x Laur x Laur x ashes x S Shox S SHE x a eve.macmillanlearning.com/ihub/assessment/f188d950-dd73-11e0-9572-0800200c9a66/d591b3f2-d5f7-4983-843c-0d00c1c0340b/f2b47861-07c4-4d1b-a1ee-e7db27d6b4ee?actualCourseld=d591b3f2-c stions estion. ct each urces. +95 Macmillan Learning Draw the product formed by the reaction of potassium t-butoxide with (15,25)-1-bromo-2-methyl-1-phenylbutane (shown). Clearly show the stereochemistry of the product. H BH (CH3)3CO-K+ +100 H3CW (CH3)3COH +85 H3CH2C +95 ossible ↓ Q Search Select Draw Templates More C H 0 bp A Erase 2Q 112 Resouarrow_forward
- Identify the structure of the PTH derivative generated after two rounds of Edman degradation.arrow_forwardUse the data below from an electron impact mass spectrum of a pure compound to deduce its structure. Draw your structure in the drawing window. Data selected from the NIST WebBook, https://webbook.nist.gov/chemistry/ m/z Relative intensity 31 0.5 30 26 29 22 28 100 27 33 26 23 15 4 • You do not have to consider stereochemistry. You do not have to explicitly draw H atoms. • In cases where there is more than one answer, just draw one. 妊 n ? Previous Nextarrow_forwardfor this question. Write the molecular formula for a compound with the possible elements C, H, N and O that exhibits a molecular ion at M+ = 98.1106. Exact Masses of the Most Abundant Isotope of Selected Elements Isotope Natural abundance (%) Exact mass 1H 99.985 1.008 12C 98.90 12.000 14N 99.63 14.003 160 99.76 15.995 Molecular formula (In the order CHNO, with no subscripts)arrow_forward
- PLEASE READ!!! I DONT WANT EXAMPLES, I DONT WANT WORDS OR PARAGRAPHS!!! PLEASE I UNDERSTAND THE BASICS BUT THIS IS AN EXCEPTION THAT EVEN THE INTERNET CANT HELP!!!! THIS IS THE THIRD TIME I'VE SENT THOSE QUESTIONS SO PLEASE DONT RESEND THE SAME STUFF, ITS NOT HELPING ME!!! I ALSO ALREADY TRIED TO DRAW THE MECHANISM MYSELF, SO IF ITS RIGHT PLEASE TELL ME OR TELL ME WHAT I HAVE TO CHANGE!!! First image: I have to SHOW (DRAWING) the mechanism (with arows and structures of molecules) NOT WORDS PLEASE! of the reaction at the bottom. Also I have to show by mecanism why the reaction wouldn't work if the alcohol was primary Second image: I have to show the mechanism (IMAGE) (with arrows and structures of the molecules) NOT WORDS PLEASE !! for the reaction on the left, where the alcohol A is added fast in one portion HOMEWORK, NOT EXAM!! ALL DETAILS ARE IN THE IMAGES PLEASE LOOK AT THE IMAGES, DONT LOOK AT THE AI GENERATED TEXT!!!arrow_forwardWrite the molecular formula for a compound with the possible elements C, H, N and O that exhibits a molecular ion at M+ = 85.0899. Exact Masses of the Most Abundant Isotope of Selected Elements Isotope Natural abundance (%) Exact mass 1H 99.985 1.008 12C 98.90 12.000 14N 99.63 14.003 160 99.76 15.995 Molecular formula (In the order CHNO, with no subscripts)arrow_forwardUse the data below from an electron impact mass spectrum of a pure compound to deduce its structure. Draw your structure in the drawing window. Data selected from the NIST WebBook, https://webbook.nist.gov/chemistry/ m/z Relative intensity 59 3.0 58 64 43 100 15 23 • You do not have to consider stereochemistry. •You do not have to explicitly draw H atoms. • In cases where there is more than one answer, just draw one. + n[] 85 // ? CH4 Previous Nextarrow_forward
- Write the molecular formula for a compound with the possible elements C, H, N and O that exhibits a molecular ion at M* = 128.0632. Exact Masses of the Most Abundant Isotope of Selected Elements Isotope Natural abundance (%) Exact mass 1H 99.985 12C 98.90 14N 99.63 160 99.76 Molecular formula 1.008 12.000 14.003 15.995 (In the order CHNO, with no subscripts)arrow_forwardCan I please get help with this? And can I please the lowest possible significant number?arrow_forwardWhat is the molar mass of a gas that takes three times longer to effuse than helium?arrow_forward
- Chemistry: Matter and ChangeChemistryISBN:9780078746376Author:Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl WistromPublisher:Glencoe/McGraw-Hill School Pub CoChemistry: Principles and ReactionsChemistryISBN:9781305079373Author:William L. Masterton, Cecile N. HurleyPublisher:Cengage Learning
- Living By Chemistry: First Edition TextbookChemistryISBN:9781559539418Author:Angelica StacyPublisher:MAC HIGHERChemistry & Chemical ReactivityChemistryISBN:9781337399074Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781133949640Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage Learning



