Tiêu đề EDX Topic 4 stiochemistry .pdf ✅

Topic 5 Formulae, Equations & Calculations 1
Topic 5 2 Stoichiometry: is the part of chemistry that deals with amounts of substance involved in chemical reactions. Molecular Formula: of a compound shows the number and type of different atoms in one molecule. Example: Water is a compound, its molecular formula is H2O 1) The formula shows that water is made up of - Hydrogen & Oxygen 2) It also shows that water contains - 2 Hydrogen atoms & 1 Oxygen atom 3) The total no. of atoms forming water is 3 Na+ Cl- Ratio 5 5 Ratio 1 1 Empirical Formula NaCl How can we deduce the formula of a compound? 1) From a model or diagrammatic representation 2) Using Valencies 1) Deducing the formula from a model or a diagram A) In a giant structure, the diagram shows the ration between ions or atoms in the compound. Empirical Formula: it’s a formula that shows that simplest whole number ratio of the different atoms or ions in a compound. No. of atoms H O No. of atoms 2 1 Molecular Formula B) In molecular compounds, the diagram tells the exact no. of atoms in the compound.
3 No. of atoms N H No. of atoms 1 3 Molecular Formula No. of atoms C O No. of atoms 1 2 Molecular Formula Group 1 Group 2 Group 3 Transition Metals Group 4 Group 5 Group 6 Group 7 Group 8 Valency 1 Valency 2 Valency 3 More than one valency Valency 4 Valency 3 Valency 2 Valency 1 Valency 0 2) Deducing the formula using valencies Valency = Valency e- (They lose e-) Valency = 8 - Valency e- (They gain e-) N H 3 1 NH3 Ca Cl 2 1 CaCl2 Na CO3- 1 1 NaCO3 Place the valency under the symbol and cross multiply. Or in case of polyatoms (radicals) place the charge and cross multiply. Topic 5