main Chemical reactions

Chemical Names

In most cases the name of a chemical tells you precisely which elements are present.

When non-metal atoms are combined with metals their name changes slightly in the name of the compound.

For example, calcium combined with oxygen will give calcium oxide. Whenever you come across a compound where the name finishes with -ide you know that this is, in fact, a combined non-metal atom.

Image	Name
	sodium chloride
	calcium oxide
	iron II sulphide

Some chemical names are more difficult to understand. The names of these chemicals need to be learned and remembered!

Image	Name	Notes
	ammonia gas	Made from nitrogen and hydrogen (Ratio 1:3)
	nitric acid	Hydrogen combined with a nitrate radical (Ratio 1:1)
	water	Its correct chemical name is hydrogen oxide! Atoms are re-arranged during a chemical reaction, they are not changed by the reaction. A chemical reaction is shown like this: .... reactant(s) product(s)   The arrow represents the reaction taking place.   The reaction shown below represents the element carbon burning in air. It combines with the oxygen gas in the air to make carbon dioxide gas. + HEAT One atom of carbon (4 bonding arms) reacts with one molecule of oxygen gas) The carbon and oxygen gas need to be heated together for this reaction to proceed. During the reaction the two oxygen atoms were separated and then joined to the carbon atom. In the next example nitrogen gas reacted with hydrogen gas to form ammonia gas.     +     HEAT One molecule of nitrogen gas reacts with three molecules of hydrogen gas. These gases need to be heated together for the reaction to proceed. The reaction produces two molecules of ammonia gas. + HEAT     +     HEAT "Matter can neither be created nor destroyed by chemical means" This is a really important rule to remember when you are making chemical equations. You must always make sure that you have the same number of each type of atom on either side of the chemical equation. You cannot lose or gain any atoms! Take another look at the two equations above: In the first equation you will find one carbon atom and two oxygen atoms on either side of the reaction arrow. In the second equation there are two nitrogen atoms and six hydrogen atoms on the reactants' side of the equation. There are the same numbers on the products' side. Atoms have neither been created or destroyed, they have simply been rearranged to make different molecules. Chemists find the identity of the products of a reaction by experimentation and observation. Study the reaction below: ..... In this reaction hydrogen sulphide gas is burnt in oxygen gas. The products of this reaction are sulphur and water. If hydrogen sulphide gas and oxygen gas are mixed in a gas jar and a burning match or taper is placed near the mouth of the gas jar. A bright, blue flame can be seen that moves down the gas jar. When the reaction is finished you can see a yellow powder on the inside of the gas jar as well as condensation. This yellow powder is the element sulphur. The arrow in the equation tells you that a solid has been made during the reaction. The condensation can be proved to be water by testing with cobalt II chloride paper which turns from blue to pink only in the presence of water. The equation below shows what happens when chalk (calcium carbonate) is heated ..... This reaction is an example of chemical decomposition by heat. The two products are calcium oxide and carbon dioxide gas. The gas can be proved to be carbon dioxide by bubbling it through lime water. Lime water is a specific test for carbon dioxide gas. No other gas will make the lime water turn "cloudy" or "milky". Most metals will react with dilute acids to give a salt and hydrogen gas. Reaction 1 Metal + acid salt + Hydrogen gas Reaction 2 In these reactions the metal replaces the hydrogen. Hydrogen gas is liberated (this is shown by the arrow pointing upwards). The other product is a salt which is formed from the chemical bonding of a metal with a non-metal component. You will notice that the type of salt produced depends on the acid used. Can you identify the reactants and the products shown in the equations above? Note: Dilute acid will have no effect on copper. Copper is not reactive enough to replace the hydrogen in this type of reaction. Sodium and potassium are far too reactive to use safely in the laboratory as the metal reactant.