Name: oxidation states in redox reactions
Uploaded: 2020-03-26T07:22:24.000Z
Duration: 4 min 56 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.9

CHEM.9.B

Redox Reactions

İndirgeme-oksidasyonun kısaltması olan redoks, elektronların net transferi ile sınıflandırılan bir kimyasal reaksiyon türüdür. Bu reaksiyonda bir molekül oksidasyon adı verilen elektron kaybeder ve diğer molekül indirgeme adı verilen elektron kazanır.
İkisi arasında ayrım yapmanıza yardımcı olması için, 'oksidasyon kaybediyor, indirgeme kazanıyor' anlamına gelen 'OIL-RIG' ifadesini hatırlayın. Oksitlenen molekül, diğer reaktanı indirgediği için indirgeyici ajan olarak adlandırılır. Benzer şekilde, indirgenen molekül, diğer molekülü oksitlediği için oksitleyici ajan olarak adlandırılır.
Artık terminolojiyi çözdüğümüze göre, bir redoks reaksiyonu örneğine, mineral magnezyum oksit oluşumuna bakalım. Reaksiyon sırasında, her magnezyum atomu iki elektron kaybeder. Böylece magnezyum oksitlenir. Her oksijen atomu iki elektron kazanır; Böylece oksijen azalır.
Bununla birlikte, tüm reaksiyonlar redoks reaksiyonları değildir. Örneğin, kalsiyum oksidin kalsiyum karbonat oluşturmak için karbondioksit ile reaksiyonu bir redoks reaksiyonu değildir. Peki, bir redoks reaksiyonunu nasıl tanımlayabiliriz?
Bunu yapmak için, reaktandan ürüne geçerken her bir elementin oksidasyon sayısını takip ediyoruz. Oksidasyon sayısı, bir atomun farklı elementlere olan bağları iyonik olsaydı sahip olacağı varsayımsal yüktür, yani elektronlar daha elektronegatif atoma atanmıştır. Bir moleküldeki oksidasyon sayılarının toplamı, toplam yüküne eşittir.
Magnezyum okside geri dönelim. Nötr bir bileşiktir, bu nedenle magnezyum ve oksijen için oksidasyon sayılarının toplamı sıfıra eşittir. Magnezyum iki elektron verebilir, bu nedenle oksidasyon sayısı artı ikidir. Oksijen iki elektron kabul edebilir, bu nedenle oksidasyon sayısı eksi ikidir.
Tepkiler nasıl? Saf nötr elementel bileşiklerin oksidasyon sayısı sıfırdır. Böylece hem magnezyum hem de oksijen sıfır oksidasyon sayıları ile başlar. Reaksiyon sırasında hem magnezyum hem de oksijenin oksidasyon sayıları değişti, bu yüzden bu bir redoks reaksiyonudur.
Şimdi, daha önce gördüğümüz kalsiyum karbonat reaksiyonuna bakalım. Her iki reaktan da nötrdür, bu nedenle her iki bileşik için oksidasyon sayılarının toplamı sıfırdır. Magnezyum oksit ile gördüğümüz gibi, kalsiyumun oksidasyon sayısı artı iki ve oksijen eksi ikidir. Daha sonra, karbondioksit molekülündeki karbonun oksidasyon sayısı artı dört ve her oksijen eksi ikidir.
Ürüne ne dersiniz? Kalsiyum artı iki ve karbon artı dört, tıpkı reaktanlarda olduğu gibi. Her oksijen eksi iki, toplam eksi altıdır ve net oksidasyon sayısı sıfırdır. Oksidasyon sayılarının hiçbiri değişmediğinden, bu bir redoks reaksiyonu değildir.
Şimdi dört tür redoks reaksiyonunu tanıtalım. Birincisi, bir atomun diğerinin yerini aldığı tek bir yer değiştirme reaksiyonudur. Bunu, bir metalin indirgendiği ve diğer metalin oksitlendiği bir termit reaksiyonunda göreceksiniz.
Bir sonraki tip, oksitlenmiş ürünler ve ısı oluşturmak için bir yakıt ve oksidan arasında meydana gelen bir yanma reaksiyonudur. Bunu laboratuvarda bir Bunsen brülörü kullanırken metanın oksijenle yanması sırasında görürsünüz.
Üçüncüsü, nitrojenin amonyak oluşturmak için hidrojen ile birleştirildiği amonyak sentezinde olduğu gibi, iki reaktanın tek bir ürün oluşturmak üzere birleştiği bir sentez reaksiyonudur.
Son olarak, dördüncü tip, bir reaktanın daha küçük bileşikler oluşturmak için bağlarını kırmak için yeterli enerjiyi emdiği bir ayrışma reaksiyonudur. Potasyum kloratın ısıtıldıktan sonra potasyum klorür ve oksijene ayrıştığı havai fişeklerde olan budur.
Bu laboratuvarda, katı bakırı bakır okside dönüştüren ve ardından tekrar katı bakıra dönüştüren çeşitli redoks reaksiyonlarını gerçekleştirecek ve tanımlayacaksınız.

redoks reaksiyonları

<h4>Oksidasyon ve İndirgeme</h4>
Bazı kimyasal reaksiyonlar, indirgeme-oksidasyon reaksiyonları veya redoks reaksiyonları olarak sınıflandırılabilir. Oksidasyon, bir atom veya iyonik molekül gibi maddenin bir veya daha fazla elektron kaybetme sürecidir ve indirgeme, maddenin bir veya daha fazla elektron kazanma sürecidir.
<h4>Oksidasyon Durumları</h4>
Bir moleküldeki her atomun kendi oksidasyon durumu veya oksidasyon numarası vardır. Oksidasyon durumu, bir molekülün serbest element formuna göre ne kadar oksitlendiğini tanımlar. Oksidasyon durumu, bir atomun diğer elementlere olan bağlarının her birinin tamamen iyonik olması durumunda sahip olacağı yük olarak ifade edilir. Bu, bağdaki elektronların daha elektronegatif atoma atandığı anlamına gelir. Serbest element formundaki bir atomun oksidasyon durumu 0 olarak tanımlanır.
Oksidasyon durumunu belirlemek için izlenen birkaç kural vardır. Grup I ve Grup II'deki elementler tipik olarak sırasıyla +1 ve +2 oksidasyon durumlarına sahiptir. Hidrojen ve oksijen tipik olarak sırasıyla +1 ve -2 oksidasyon durumlarına sahiptir ve halojenler genellikle -1 oksidasyon durumuna sahiptir. Ek olarak, bir moleküldeki atomların oksidasyon durumları her zaman molekül üzerindeki yüke eklenir. Bu nedenle, yukarıda listelenmeyen bir atomun oksidasyon durumu genellikle çıkarılabilir. Örneğin, nötr bir molekül olan karbondioksiti (CO2) düşünün. İki oksijen molekülünün her biri -2'ye katkıda bulunuyorsa, oksijenlerden -4'ü iptal etmek için karbonun oksidasyon durumu +4 olmalıdır.
Daha genel bir yaklaşım için, molekülün Lewis yapısını çizin, farklı atomlar arasındaki bağları tanımlayın ve her bağı daha elektronegatif atoma atayın. Ardından, her bir atomdaki elektron sayısını sayın, her bağ iki elektrona katkıda bulunur. Oksidasyon sayısını elde etmek için o atomun standart değerlik elektron sayısından şu anda atom üzerinde bulunan elektron sayısını çıkarın.
Tekrar karbondioksiti düşünün. Her oksijenin iki yalnız elektron çifti vardır ve merkezi karbona bir çift bağ ile bağlanır. Oksijen, karbondan daha elektronegatiftir, bu nedenle dört elektronu oluşturan her C=O bağı, oksijenine atanır. Böylece, her oksijene toplam sekiz elektron atanır (dördü yalnız çiftlerden ve dördü çift bağdan) ve karbona hiçbiri atanır. Oksijen için varsayılan değerlik elektron sayısı altıdır, bu nedenle her oksijen için oksidasyon sayısı 6 – 8 = -2'dir. Karbon için varsayılan değerlik elektron sayısı dörttür, bu nedenle karbon için oksidasyon sayısı 4 – 0 = +4'tür.
<h4>Redoks Reaksiyonları</h4>
Tüm kimyasal reaksiyonlar redoks reaksiyonu olarak sınıflandırılmaz. Redoks reaksiyonu, bir atomun oksidasyon durumunda bir değişikliğin olduğu herhangi bir reaksiyondur. Bu nedenle, bir reaksiyonun bir redoks reaksiyonu olup olmadığını kontrol etmek için, reaktanlar ve ürünlerdeki her bir atomun oksidasyon durumlarını belirleyin ve herhangi bir değişiklik olup olmadığına bakın.
Birçok redoks reaksiyonu, elektronların doğrudan bir molekül veya atomdan diğerine transferini içerir. Bu reaksiyonlarda, bir molekül veya atom bir elektron kazanırsa, başka bir molekül veya atom bir elektron kaybetmek zorundadır. Oksidasyon ve indirgeme tanımlarını hatırlamanın basit bir yolu, şu anlama gelen OIL-RIG ifadesidir: Oxidation Is Losing – Reduction Is Gaining.
Elektron kazanan molekül indirgenmektedir, ancak diğer molekülü oksitlediği için oksidan veya oksitleyici ajan olarak adlandırılır. Benzer şekilde, bir elektron kaybeden molekül oksitlenir, ancak diğer molekülü indirgediği için indirgeyici veya indirgeyici ajan olarak adlandırılır.
Tipik olarak redoks işlemlerini içeren dört ana reaksiyon türü vardır.
<ol>
	<li style="font-size:17px">Tek Yer Değiştirme Reaksiyonu: Bir atom, bir bileşiğin parçası olan başka bir atomun yerini alır ve onun yerini alır.</li>
	<li style="font-size:17px">Yanma Reaksiyonu: Bir bileşik, güçlü bir oksidan, tipik olarak oksijen gazı ile indirgenir. Hidrokarbonlar ve organik bileşikler arasında meydana gelen yanma reaksiyonları tipik olarak karbondioksit ve su üretir.</li>
	<li style="font-size:17px">Sentez Reaksiyonu: İki reaktan tek bir ürün oluşturur.</li>
	<li style="font-size:17px">Ayrışma Reaksiyonu: Tek bir reaktan iki veya daha fazla ürüne ayrılır.</li>
</ol>
<h4>Başvuru</h4>
1. Harris, DC (2015). Kantitatif Kimyasal Analiz. New York, NY: W. H. Freeman ve Şirketi.

Redoks Reaksiyonları

Oksidasyon ve İndirgeme
Bazı kimyasal reaksiyonlar, indirgeme-oksidasyon reaksiyonları veya redoks reaksiyonları olarak sınıflandırılabilir. Oksidasyon sürecidir ...

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JoVE Lab Manual

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oxidation states in redox reactions

Oxidation states help identify redox reactions. In a redox reaction, oxidation is the loss of one or more electrons, and reduction is the gain of one or more electrons. These reactions are often tracked by changes in oxidation state, also called oxidation number.

Each atom in a molecule has an oxidation state. This number shows how oxidized an atom is compared with its free elemental form. It is written as the charge an atom would have if every bond were purely ionic. In that model, bonding electrons are assigned to the more electronegative atom. An atom in its elemental form has an oxidation state of 0.

Several rules help determine oxidation states. Group I elements usually have +1, and Group II elements usually have +2. Hydrogen is typically +1, oxygen is typically -2, and halogens usually are -1. The oxidation states in a molecule or ion must add up to the total charge, so unknown values can often be found from the rest.

Carbon dioxide is a clear example. CO2 is neutral, so its total oxidation states must add to zero. Each oxygen is usually -2, so carbon must be +4 to balance the two oxygens. Another way to find oxidation numbers is to draw the Lewis structure, assign each bond to the more electronegative atom, and count electrons on each atom.

In CO2, oxygen is more electronegative than carbon, so each C=O bond is assigned to oxygen. Each oxygen gets eight electrons total, including lone pairs and bonding electrons. Oxygen has six valence electrons by default, so its oxidation number is 6 - 8 = -2. Carbon has four valence electrons by default and is assigned none, so its oxidation number is 4 - 0 = +4.

A reaction is a redox reaction when an atom’s oxidation state changes from reactants to products. To check for redox, compare oxidation states on both sides of the reaction. Many redox reactions also involve direct electron transfer between atoms or molecules. If one species gains an electron, another must lose one.

The phrase OIL-RIG helps remember the process: oxidation is losing, and reduction is gaining. The species that gains electrons is reduced, but it is also called the oxidizing agent or oxidant because it oxidizes the other species. The species that loses electrons is oxidized, but it is also called the reducing agent or reductant because it reduces the other species.

Four major reaction types often involve redox processes. In single displacement reactions, one atom replaces another atom in a compound. In combustion reactions, a compound is reduced by a strong oxidant, usually oxygen gas, and hydrocarbons or other organic compounds often produce carbon dioxide and water. In synthesis reactions, two reactants form one product. In decomposition reactions, one reactant breaks into two or more products.

Oxidation States in Redox Reactions

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Alcohol tests can help sort alcohols by structure and reactivity. Alcohols are organic molecules with a hydroxyl group attached to an alkyl or aryl group, written as ROH. If the carbon with the hydroxyl group has one R group, the alcohol is primary. If it has two R groups, it is secondary. If it has three R groups, it is tertiary. Alcohols can also be aromatic when they contain a benzene ring. Phenol is the simplest aromatic alcohol. To identify an alcohol, chemists can use its chemical...

chemistry

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Learn how oxidation states reveal redox reactions, how to assign oxidation numbers, and why oxidation, reduction, and agents matter in chemistry.

Oxidation States in Redox Reactions | JoVE K12

Florida Department of Education

Physical Science

SC.912.P.8

SC.912.P.8.10

Georgia Standards of Excellence

9-12

SC3.

Indicators of Chemical Reactions

Redoks Reaksiyonları öğretimine bu 6 dakikalık eğitmen rehberiyle hazırlanın. JoVE Lab Manual üzerindeki Chemistry laboratuvarı için temel hazırlık adımlarını kapsar.

Chemistry içinde Redoks Reaksiyonları Eğitmen Hazırlığı - 4.9K+ Görüntülenme | JoVE Lab Manual

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Chemistry içinde Redoks Reaksiyonları Öğrenci Protokolü - 28K+ Görüntülenme | JoVE Lab Manual

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CHEM.9.C

Science concepts. The student understands how matter is accounted for in chemical reactions. The student is expected to:

Oxidation States in Redox Reactions

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