However, it must be remembered that the pure acids contain covalently bonded molecules. Exercise 1-B Ionically bonded compounds are named according to the two ions involved, the cation being given first, so that Al2O3 is aluminum oxide and Cr OH 3 is chromium III hydroxide. Note that the bracketed Roman numerals are used for metals, which have multiple oxidation states, to give the oxidation number of the metal in the compound, which is usually equal to the charge on the cation. The ending of the names of ions often indicate their composition.
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However, it must be remembered that the pure acids contain covalently bonded molecules. Exercise 1-B Ionically bonded compounds are named according to the two ions involved, the cation being given first, so that Al2O3 is aluminum oxide and Cr OH 3 is chromium III hydroxide. Note that the bracketed Roman numerals are used for metals, which have multiple oxidation states, to give the oxidation number of the metal in the compound, which is usually equal to the charge on the cation.
The ending of the names of ions often indicate their composition. For example the ending —ide usually indicates just the element with an appropriate negative charge sulfide is S The ending -ate usually indicates the ion contains the element and oxygen atoms sulfate is SO The ending —ite, also indicates an ion containing oxygen, but less oxygen than the —ate e. The formula for glucose, which is a molecular covalent compound, is C6H12O6.
This tells us that a molecule of glucose contains six carbon atoms, twelve hydrogen atoms and six oxygen atoms. Sometimes brackets are used in molecular formulas to indicate the way in which the atoms are bonded together. Formulas of this type are know as structural formulas and are discussed in much more detail in Section The formulas of covalent compounds have to be memorised, though in some cases it is possible to deduce the formula from the name and vice versa; for example dinitrogen pentoxide N2O5.
Sometimes compounds are hydrated, that is they contain water molecules chemically bonded into the structure of the crystals. This is known as water of crystallisation or hydration and it is indicated by the formula for water following the formula of the substance and separated from it by a dot.
When the crystals are heated this water is frequently given off to leave the anhydrous salt Na2SO4. Determine the formula of cadmium benzoate. Analysis shows that calcium and phosphorus are present in a mole ratio of Which of the following best represents the composition of the ore?
If the formula of praseodymium oxide is PrO2, Determine the formula of praseodymium sulfate. Write the formulas of the following common compounds: a Sulfuric acid b Sodium hydroxide c Nitric acid d Ammonia e Hydrochloric acid f Ethanoic acid g Copper II sulfate h Carbon monoxide i Sulfur dioxide j Sodium hydrogencarbonate 5.
Write the formulas of the following substances: a Sodium chloride b Copper II sulfide c Zinc sulfate d Aluminium oxide e Magnesium nitrate f Calcium phosphate g Hydroiodic acid h Ammonium carbonate i Methane j Phosphorus pentachloride Stoichiometric Relationships A chemical equation is a record of what happens in a chemical reaction.
It shows the formulas molecular formulas or formula units of all the reactants on the left hand side and all the products on the right hand side. It also gives the number of each species that are required for complete reaction.
The example below shows the reaction of hydrogen and oxygen to produce water. Hence hydrogen gas is H2 not H and chlorine gas is Cl2 not Cl. The two non-gaseous halogens are also diatomic and so bromine is always written as Br2 and iodine as I2.
The first stage in producing an equation is to write a word equation for the reaction. These multiply the number of atoms of the substances in the formula by that factor and represent the number of moles of the species required. In the example above, there are two chlorines on the right hand side, but only one on the left hand side. Similarly the hydrogen atoms do not balance. Scaling this up means that one mole of calcium carbonate reacts with two moles of hydrochloric acid to produce one mole of calcium chloride, one mole of carbon dioxide and one mole of water.
The amounts of substances in a balanced equation are known as the stoichiometry of the reaction, hence these equations are sometimes referred to as stoichiometric equations. One corollary of balancing chemical equations is that as a result mass is conserved. Note that the formulas of compounds can never be changed, so balancing the equation by altering the subscripts, for example changing calcium chloride to CaCl3 or water to H3O, is not allowed. It is sometimes helpful to show the physical state of the substances involved and this can be done by a state symbol placed after the formula.
The state symbols used are s solid, l - liquid, g - gas and aq - aqueous solution. State symbols should be used as a matter of course as it gives more information about a reaction and in some cases, such as when studying thermochemistry, where their use is vital because state changes involve the gain or loss of energy. This is particularly true for precipitation reactions, acid-base reactions see Section 8. An example would be the reaction between aqueous lead nitrate and aqueous sodium chloride to precipitate lead chloride and leave a solution of sodium nitrate.
The hydrated nitrate ions and sodium ions are present in both the reactants and products and so do not take part in the reaction; they are known as spectator ions.
The examples and questions do not necessarily reflect the views of the official senior examining team appointed by the International Baccalaureate Organisation. In writing this book the authors hope to share material that they have found useful over the years with other Chemistry teachers in the context of the revised International Baccalaureate Chemistry syllabus. Those familiar with this course will find a close correlation between the order in which the book deals with topics and the order in which they appear in the syllabus. The text is accompanied by a series of exercises, most of which have accompanying answers on the CD, making this a useful resource for self-study to reinforce normal classroom teaching. The arrangement of material according to the IBO syllabus guide is clearly indicated in the Table of Contents, the topic lists on the chapter title pages and also with side tabs for Core, AHL, Options and Extended.
IB Higher Level Chemistry Paper Analysis
The most widely used biology textbook worldwide for high school and universities. The only downside is its price and weight, however definitely worth the price. An excellent summary of the course, but which will need to be augmented by your teacher over the two years. It provides brief and easy to understand explanations of concepts and information.