Name: reading chemical equations and balancing them
Uploaded: 2020-09-03T13:38:26.000Z
Duration: 3 min 10 s
Channel: JoVE

K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.4.2

Chemical Equations

Химические реакции включают химические превращения одного или нескольких веществ в другие вещества. Реакцию обычно представляют с помощью химического уравнения, в котором используются химические формулы для представления участвующих атомов, молекул или соединений. Вещества, присутствующие в начале реакции и расходуемые в процессе, называются реагентами.Реагенты указаны в левой части уравнения. Вещества, образующиеся в ходе реакции, называются продуктами и указываются в правой части уравнения. Стрелка, разделяющая реагенты и продукты, показывает направление реакции.Различные состояния вещества изображены с помощью сокращений в скобках. Химическая реакция подчиняется закону сохранения массы, при котором сохраняются общие массы всех участвующих элементов. Следовательно, совокупное количество атомов каждого элемента будет совпадать как в реагентах, так и в продуктах.Химические уравнения уравновешиваются с использованием числовых коэффициентов, отражающих фактическое количество атомов, участвующих в реакции. При балансировании любого химического уравнения важно изменять только числовые коэффициенты, а не числовые индексы, которые определяют идентичность соединения. Общие рекомендации помогают эффективно проиллюстрировать и скорректировать химическое уравнение.Например, сгорание жидкой бензойной кислоты с образованием газообразного диоксида углерода и воды первоначально представляют с использованием скелетного химического уравнения. Затем уравновешивают атомы, сначала в соединениях, а затем атомы свободных элементов. Включение коэффициентов семь и три перед формулами для углекислого газа и воды уравновешивает атомы углерода и водорода.Дробный коэффициент пятнадцать вторых уравновешивает атомы кислорода. Дробные коэффициенты преобразуются в целые числа путем умножения всего уравнения на знаменатель. Суммарное число атомов каждого элемента равно с обеих сторон сбалансированного уравнения.В химических уравнениях, представляющих реакции с участием ионных соединений, сначала уравновешивают катионы, а затем анионы. Многоатомные ионы всегда уравновешивают как единое целое. Например, водный сульфат алюминия реагирует с водным гидроксидом кальция с образованием твердого гидроксида алюминия и твердого сульфата кальция.Используя скелетное уравнение, уравновешивают катионы алюминия и кальция, за ними следуют анионы многоатомного гидроксида и сульфат-ионов. Наконец, коэффициенты корректируются для получения общего сбалансированного уравнения.

Химические уравнения

Химические уравнения представляют собой идентичность и относительные количества веществ, участвующих в химической реакции. Вещества, проходящие реакцию, называются реагентами, а их формулы размещены на левой стороне уравнения. Вещества, образуемые в результате реакции, называются продуктами, а их формулы размещены в правой части уравнения. Знак плюс (+) отделяет отдельные формулы восстановителя и продукта, а стрелка (→) разделяет сторону восстановителя и продукта (левую и правую) уравнения. Относительные числа реактанта и видов продукции представлены численными коэффициентами, размещенными сразу слева от каждой формулы. Коэффициент 1 обычно не отображается. Наименьшие возможные коэффициенты целого числа обычно используются в химическом уравнении, и они интерпретируются как коэффициенты. Например, метан и кислород реагируют на выбросы углекислого газа и воды в соотношении 1:2:1:2.  
 
 <img alt=""Eq1"" src=""https://www.jove.com/files/core/CDNSource/lessons/1019/1019_Equations-01.png"" style=""height: 40px;"" />
 
 Это соотношение указывает на то, что наименьшие возможные коэффициенты метана, кислорода, углекислого газа и воды составляют 1, 2, 1 и 2 соответственно. Коэффициенты могут быть интерпретированы в отношении любой единицы количества (числа), поэтому это уравнение можно правильно прочитать многими способами, включая: 
 
 i. Одна молекула метана и две молекулы кислорода реагируют с выходом одной молекулы углекислого газа и двух молекул воды. 
 
 ii. Один моль молекул метана и 2 моля молекул кислорода реагируют производят 1 моль молекул углекислого газа и 2 моля молекул воды.  
 
 Физические состояния реагентов и продуктов в химических уравнениях очень часто обозначаются аббревиатурой в скобках после формул. Стандартные сокращения включают & lsquo; s & rsquo; для твердых веществ & lsquo; l & rsquo; для жидкостей & lsquo; g & rsquo; для газов и & lsquo; водный & rsquo; для веществ, растворенных в воде. 
 
 <h4>Уравнения балансировки </h4>
 
 В сбалансированном уравнении количество атомов для каждого элемента, участвующего в реакции, одинаково на стороне восстановителя и продукта, тем самым удовлетворяя закон сохранения материи. Сбалансированное уравнение можно подтвердить, добавив числа атомов по обеим сторонам стрелки и сравнив эти суммы, чтобы обеспечить их равенство. Обратите внимание, что количество атомов для данного элемента рассчитывается путем умножения коэффициента любой формулы, содержащей этот элемент, на индекс элемента в формуле. Если элемент появляется в нескольких формулах на заданной стороне уравнения, то число атомов, представленных в каждом из них, должно быть вычислено, а затем добавлено вместе. 
 
 Для балансировки уравнения коэффициенты уравнения можно изменить по мере необходимости. Иногда удобно использовать дроби вместо целых чисел в качестве промежуточных коэффициентов в процессе балансировки химического уравнения. После достижения баланса все коэффициенты уравнения могут быть умножены на целое число, чтобы преобразовать дробные коэффициенты в целые числа без увеличения баланса атома.  
 
 Например, реакция этана (C2Р6) с кислородом дает воду и углекислый газ, которые могут быть представлены следующим несбалансированным уравнением: 
 
 <img alt=""Eq2"" src=""https://www.jove.com/files/core/CDNSource/lessons/1019/1019_Equations-02.png"" style=""height: 40px;"" />
 
 Несбалансированное уравнение содержит:  
 <table style="margin-left: auto; margin-right: auto;">
 <tbody style="border: 1px solid black;">
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">Атомы</td>
 <td style="color: black; border: 1px solid black; text-align: center;">Реагент</td>
 <td style="color: black; border: 1px solid black; text-align: center;">Продукт</td>
 <td style="color: black; border: 1px solid black; text-align: center;">Сбалансированы?</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">C</td>
 <td style="color: black; border: 1px solid black; text-align: center;">2</td>
 <td style="color: black; border: 1px solid black; text-align: center;">1</td>
 <td style="color: black; border: 1px solid black; text-align: center;">Нет</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">H</td>
 <td style="color: black; border: 1px solid black; text-align: center;">6</td>
 <td style="color: black; border: 1px solid black; text-align: center;">2</td>
 <td style="color: black; border: 1px solid black; text-align: center;">Нет</td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">O</td>
 <td style="color: black; border: 1px solid black; text-align: center;">2</td>
 <td style="color: black; border: 1px solid black; text-align: center;">3</td>
 <td style="color: black; border: 1px solid black; text-align: center;">Нет</td>
 </tr>
 </tbody>
 </table>
 
 Чтобы сбалансировать количество атомов углерода и водорода, умножьте значение CO2 на коэффициент 2 и умножьте значение H2О на коэффициент 3, соответственно. Это изменяет общее количество атомов кислорода на продукте на 7. Чтобы сбалансировать количество атомов кислорода, умножьте кислород на дробный коэффициент 7/2. Это первоначальное равновесие атомов углерода, водорода и кислорода путем изменения коэффициентов реактантов и продуктов дает временное сбалансированное уравнение:  
 
 <img alt="Eq3" src="https://www.jove.com/files/core/CDNSource/lessons/1019/1019_Equations-03.png" style="height: 40px;" />
 
 Обычное сбалансированное уравнение с целочисленными коэффициентами вычисляется путем умножения каждого коэффициента на 2 для создания уравнения: 
 
 <img alt="Eq4" src="https://www.jove.com/files/core/CDNSource/lessons/1019/1019_Equations-04.png" style="height: 40px;" />
 
 Этот текст адаптирован из <a href="https://openstax.org/books/chemistry-2e/pages/4-1-writing-and-balancing-chemical-equations">Openstax, Химия 2е изд., раздел 4.1: Написание и балансировка химических уравнений</a>.

Химические уравнения представляют собой тождество и относительное количество веществ, участвующих в химической реакции. Вещества, участвующие в реакции, являются ...

Education

JoVE Core

Химия

Один

Molecules, Compounds, and Chemical Equations

Молекулы, соединения и химические уравнения

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ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

reading chemical equations and balancing them

Chemical equations show the identities and relative amounts of substances in a chemical reaction. The substances that react are called reactants, and their formulas are written on the left side of the equation. The substances formed are called products, and their formulas are written on the right side. A plus sign (+) separates formulas on the same side, and an arrow (→) shows the change from reactants to products.

The numbers in a chemical equation are shown with coefficients. A coefficient is the number written in front of a formula. A coefficient of 1 is usually not written. The smallest whole-number coefficients are commonly used, and they work as ratios. For example, methane and oxygen react to form carbon dioxide and water in a 1:2:1:2 ratio.

That ratio can be read in more than one way. It can mean 1 methane molecule and 2 oxygen molecules make 1 carbon dioxide molecule and 2 water molecules. It can also mean 1 mole of methane molecules and 2 moles of oxygen molecules make 1 mole of carbon dioxide molecules and 2 moles of water molecules. Chemical equations may also include physical states after the formulas. Common state labels are s for solid, l for liquid, g for gas, and aq for substances dissolved in water.

A balanced chemical equation has the same number of atoms for each element on both sides. This follows the law of conservation of matter. To check balance, count the atoms on the reactant side and the product side and compare the totals. To find the number of atoms in a formula, multiply the coefficient by the subscript. If an element appears in more than one formula on one side, add all of those atoms together.

Balancing a chemical equation means changing coefficients, not the formulas themselves. Fractions can be used as temporary coefficients during balancing. For the reaction of ethane with oxygen, carbon and hydrogen are balanced first by placing 2 in front of carbon dioxide and 3 in front of water. That leaves 7 oxygen atoms on the product side, so oxygen gets a fractional coefficient of 7/2. The final equation is then multiplied by 2 to turn all coefficients into whole numbers without changing the balance.

Reading Chemical Equations and Balancing Them

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chemical equations

Chemical equations show the identities and relative amounts of substances in a chemical reaction. The substances that react are called reactants, and their formulas are written on the left side of the equation. The substances formed are called products, and their formulas are written on the right side. A plus sign (+) separates formulas on the same side, and an arrow (→) shows the change from reactants to products. The numbers in a chemical equation are shown with coefficients. A coefficient...

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Reading Chemical Equations and Balancing Them

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