Chemistry: Writing and Balancing Equations?

firstly, in writing up a chemical equation, you must know the type of reation that takes place. for example, metals + acid = salt + hydrogen gas, acid+base=salt and water,etc.secondly,know with subtances you want to react. thirdly know the symbol of the element or the chemical formula ofthe compound.below are the balanced chemical equations to your questions 1) AL2(SO4)3+6NAOH=2AL(OH)3+3NA2SO4. (notice the nubers before the formulae of the compounds).in balancing chemical equations,make sure that the numbers of atoms on one side of the equation is equal to the # of atoms on the other side of the equation. 2) Mg + 2H2O =Mg(OH)3 + H2 3) 3K2HCO3 + 3H3PO4= 3K2HPO4 + 3CO2+ 3H2O