A substitution reaction occurs when an exchange of elements in the reactants takes place. The initial reactants are transformed or 'swopped around' to give a final product. A simple example of a reaction like this is shown below:
Some simple examples of substitution reactions are shown below:
In this example, a chlorine atom and a hydrogen atom are exchanged to create a new product.
In this example, four waters and four chlorines are exchanged to create a new product.
Addition, substitution and elimination reactions
Refer to the diagram below and then answer the questions that follow:
Is this reaction an example of substitution, elimination or addition?
Give a reason for your answer above.
The following diagram shows the reactants in an addition reaction.
Draw the final product in this reaction.
What is the chemical formula of the product?
The following reaction takes place:
Is this reaction a substitution, addition or dehydration reaction? Give a reason for your answer.
Consider the following reaction:
Which one of the following best describes the type of reaction which takes place?
Redox reaction
Acid-base reaction
Dehydration reaction
Summary
There are many different
types of reactions that can take place. These include acid-base, acid-carbonate, redox, addition, substitution and elimination reactions.
The
Arrhenius definition of acids and bases defines an acid as a substance that increases the concentration of hydrogen ions (H
or H
O
) in a solution. A base is a substance that increases the concentration of hydroxide ions (OH
) in a solution. However this definition only applies to substances that are in water.
The
Bronsted-Lowry definition is a much broader one. An
acid is a substance that
donates protons and a
base is a substance that
accepts protons .
In different reactions, certain substances can act as both an acid and a base. These substances are called
ampholytes and are said to be
amphoteric . Water is an example of an amphoteric substance.
A
conjugate acid-base pair refers to two compounds in a reaction (one reactant and one product) that transform or change into the other through the loss or gain of a proton.
When an acid and a base react, they form a
salt and water. The salt is made up of a cation from the base and an anion from the acid. An example of a salt is sodium chloride (NaCl), which is the product of the reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl).
The reaction between an acid and a base is a
neutralisation reaction.
Titrations are reactions between an acid and a base that are used to calculate the concentration of one of the reacting substances. The concentration of the other reacting substance must be known.
In an
acid-carbonate reaction , an acid and a carbonate react to form a salt, carbon dioxide and water.
A
redox reaction is one where there is always a change in the oxidation numbers of the elements that are involved in the reaction.
Oxidation is the loss of electrons and
reduction is the gain of electrons.
When two or more reactants combine to form a product that contains all the atoms that were in the reactants, then this is an
addition reaction . Examples of addition reactions include the reaction between ethene and bromine, polymerisation reactions and hydrogenation reactions.
A reaction where the reactant is broken down into one or more product, is called an
elimination reaction . Alcohol dehydration and ethane cracking are examples of elimination reactions.
A
substitution reaction is one where the reactants are transformed or swopped around to form the final product.
Summary exercise
Give one word/term for each of the following descriptions:
A chemical reaction during which electrons are transferred
The addition of hydrogen across a double bond
The removal of hydrogen and halogen atoms from an alkane to form an alkene
For each of the following, say whether the statement is true or false. If the statement is false, re-write the statement correctly.
The conjugate base of NH
is NH
.
The reactions
and
are examples of redox reactions.
For each of the following questions, choose the one correct statement from the list provided.
The following chemical equation represents the formation of the hydronium ion:
In this reaction, water acts as a Lewis base because it...
accepts protons
donates protons
accepts electrons
donates electrons
(IEB Paper 2, 2005)
When chlorine water (Cl
dissolved in water) is added to a solution of potassium bromide, bromine is produced. Which one of the following statements concerning this reaction is correct?
Br
is oxidised
Cl
is oxidised
Br
is the oxidising agent
Cl
is the oxidising agent
(IEB Paper 2, 2005)
The stomach secretes gastric juice, which contains hydrochloric acid. The gastric juice helps with digestion. Sometimes there is an overproduction of acid, leading to heartburn or indigestion. Antacids, such as milk of magnesia, can be taken to neutralise the excess acid. Milk of magnesia is only slightly soluble in water and has the chemical formula Mg(OH)
.
Write a balanced chemical equation to show how the antacid reacts with the acid.
The directions on the bottle recommend that children under the age of 12 years take one teaspoon of milk of magnesia, whereas adults can take two teaspoons of the antacid. Briefly explain why the dosages are different.
Why is it not advisable to take an overdose of the antacid in the stomach? Refer to the hydrochloric acid concentration in the stomach in your answer.
In an experiment, 25.0 cm
of a standard solution of sodium carbonate of concentration 0.1 mol.dm
was used to neutralise 35.0 cm
of a solution of hydrochloric acid.
Write a balanced chemical equation for the reaction.
Anatomy is the study of internal structure of an organism while physiology is the study of the function/relationship of the body organs working together as a system in an organism.
It depends on the type of infection. Bacterial, fungal, parasitic or viral?
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if you can share the sign ad symptoms of the skin infection then u geh the treatment cox they're different sign ad symptoms of skin infection with different treatment
The lymphatic system plays several crucial roles in the human body, functioning as a key component of the immune system and contributing to the maintenance of fluid balance. Its main functions include:
1. Immune Response: The lymphatic system produces and transports lymphocytes, which are a type of
asegid
to transport fluids fats proteins and lymphocytes to the blood stream as lymph
Adama
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