The Reactivity Series

The reactivity series is a way of ranking elements, usually metals, according to their reactivity. This is useful because it allows us to work out which elements will displace others in compounds, and has uses in other parts of chemistry such as resistance to corrosion through the use of sacrificial metals. This post details the different reaction types that can be analysed using the reactivity series.

Chemistry - reaction types - reactivity

    High reactivity
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Hydrogen
Copper
Silver
Gold
Low reactivity  

The reactivity series is used to predict the outcome of displacement reactions. In a displacement reaction, there is more than one element of a certain 'type' available to be in the compound. To explain what I mean by 'type', consider this:

Magnesium + copper oxide ---> Magnesium oxide + Copper

The copper is paired with the oxygen, but the magnesium could also bond with the oxygen. There are two elements competing for a place, and so the more reactive element will take that place. It does this by displacing the less reactive element.

Oxidation and reduction
Oxidation and reduction are ways of describing what has happened to an element or ion during a reaction. It is, as the name suggests, relevant to oxygen, but not exclusively.

• A substance has been oxidized if it gains oxygen. Oxidation is gain of oxygen.
•  A substance has been reduced if it loses oxygen. Reduction is loss of oxygen.
• A reducing agent is something that reduces something else.
• An oxidizing agent is something that oxidizes something else.

It can refer to the gain or loss of electrons as well. This is important to know and understand when you study the industrial chemistry topic. 

• Loss of electrons is oxidation.
• Gain of electrons is reduction

You can use the memory aid 'OIL RIG' to help you remember. Oxidation Is Loss, Reduction Is Gain. This is not to be confused with the gain or loss of oxgyen, because the gain of oxygen is oxidation, but the gain of electrons is reduction.


A REDOX reaction is one in which one element or ion is reduced, and another, different element or ion is oxidised.

Reactions of metals with water or acids uses the same rule, but instead of a metal displacing a metal it may displace hydrogen or carbon in the water or acid. Hydrogen and carbon have their places in the reactivity series too.

Reactions of metals with water -  Metals above hydrogen in the reactivity series react with water or steam to produce hydrogen.  Metals below hydrogen in the reactivity series don’t react with water or steam - they cannot displace the hydrogen.

Reactions of metals with dilute acids -  The pattern is the same as for the reaction between metals and water, except In each case the reaction is more vigorous

    We can use the reactivity series to make predictions about the results of a reaction. Given the opportunity and the right conditions, a more reactive element will always displace a less reactive one in a compound, but a less reactive one will not naturally displace a more reactive one.

Oxygen and Oxides

Oxygen is quite a common element - it occurs naturally in the atmosphere. It combines with many other elements to make compounds that have very different properties. This post details the properties of oxygen and its compounds, and how the compounds can be tested for, identified or made.

Chemistry - Oxygen and Oxides


Unpolluted, dry air is made up of approximately 78.1% Nitrogen, 21% Oxygen, 0.9% Argon and 0.04% Carbon Dioxide. Oxygen is very easy to test for as it relights a glowing splint.

Identifying and testing for oxide compounds
There are two types of oxide compounds: metal oxides and non-metal oxides.
Most Metals Oxides don’t either react with, or dissolve in, water – those that do tend to form alkaline solution. Non-metal oxides often react with water to form acidic solutions – common exceptions are water and carbon monoxide.


Carbon Dioxide
Oxygen and carbon can form the covalent compound carbon dioxide. It can be made using the reaction  between dilute hydrochloric acid and calcium carbonate (also known as marble chips).
Carbon dioxide can be tested for with lime water. When mixed, the lime water turns a milky colour. Alternatively, you can test for it using a glowing splint. While oxygen alone will fuel a fire, carbon dioxide makes a glowing splint go out. Carbon dioxide is is used in fizzy drinks because it dissolves in water under pressure, and to put out electrical fires where using water could cause problems.






This article is due to be added to shortly.

RAMS and Moles

Chemistry - RAMS and Moles

A Mole is a unit of measurement used to express the amount of a substance. It is equal to the number of atoms or molecules in 12g of Carbon-12 (6.023×10^23). -1 This unit of measurement is used instead of grams because one mole of any substance contains the same number of molecules, regardless of its density.

The Relative Atomic Mass of an element is the weighted average mass of the isotopes of the element. It is measured on a scale on which a Carbon – 12 atom has a mass of exactly 12 units.

Relative Formula Mass is the term used to describe the RAM of a compound.

Number of Moles = mass (g)/mass of 1 mole (g)

Percentage Mass of an   = RAM × Number of that element/RFM of compound × 100                               element in a compound

Finding the Empirical Formula of a Compound

1.     List all the elements in the compound

2.     Underneath them, write their experimental masses or percentages

3.     Divide each mass or percentage by the RAM for that particular element

4.     Turn the results into a ratio (by dividing them all by the same number)

5.     Simplify the Ratio until you have it in its simplest form

Empirical Formula Calculations involving hydrated salts

When some substances crystallize from a solution, water becomes chemically bonded to the salt. The salt is said to be hydrated.

Finding the n in BaCl2.nH2O

To find n, the number of water molecules, you have to find the ratio of BaCl2 to the number of moles of water. It’s just another empirical formula!

1.     Find out the masses of water and the other substances in the solution

2.     Divide these by the respective RFM/RAM’s

3.     Turn the results into a ratio

4.     Find the Ratio in its simplest form

Moles in a Solution

A 1M Solution contains 1 Mole per litre; a 2M Solution contains 2 Moles per Litre etc. 

Number of Moles = Volume in Litres × Moles Per Litre of Solution

Making salts of different solubility

Chemistry - Acids, bases and salts - Salts of different solubility

This post is about how to make salts of different solubility through mixing compounds. Different methods are required for different levels of solubility and there are three categories namely: Insoluble salts, Soluble salts of low reactivity and Soluble salts of high reactivity. 

Insoluble salts

To make a pure sample of an insoluble salt, a precipitation reaction is used. A precipitate is a fine solid that is formed by a chemical reaction involving liquids or gases.

Two ionic solutions come together. In either of the pairs the attractions aren’t strong enough for the ions to stick together but now a pair is formed through strong bonds – the precipitate. The other ions have not changed at all, and are therefore spectator ions.

To choose what to mix, take one solution that has the appropriate positive ion and one solution that contains the negative ion.

To claim the salt, ‘filter, wash and dry the precipitate’.

Making Sodium, Potassium and Ammonium salts

This is why you can’t add an excess solid to a solution: the solid would react with the solution, but the excess would just dissolve in the water present, making it impossible to filter.

This problem is solved by doing a titration. Usually, sodium, potassium hydroxide and ammonia solution would be used, but their carbonates can also be used. These solutions are alkaline so the end-point can be determined with an indicator. Usually methyl orange is used. Yellow indicates too little acid and red too much, making orange the endpoint.

The experiment is run twice with indicator to find the correct volumes of each, and then it is performed again without the indicator with the correct volumes.

Finish by evaporating the water until crystals form upon cooling, and then leave the solution to crystallise on its own.

Making other soluble salts

This technique is used with

·       Acid + metal

·       Acid + metal oxide or hydroxide

·       Acid + carbonate

You add the solid to the acid in excess to ensure all the acid is used up, and then filter off the excess solid. The rest is heated until crystals form upon cooling.

You will usually heat the reaction unless it is a carbonate or magnesium.