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Chemical Equations
Things you should already know…
Elements from the periodic tableYour polyatomic ionsTheBrINClHOF’sHow to write ionic and covalent compounds namesThe symbols for solid, liquid, gas, and aqueousHowto interpret word problems
Other Things to Know
Whenmetals are just named (i.e. Lead) this is simply the solid pure element ( i.e.Pb(s))When you are told something is “bubbled in” that means a gas form of that element is being addedEx. “hydrogen is bubbled into a solution of…”Is written as: H2(g) + … …
More Things You Should Know
Solutionsare all aqueous (aq)Ex: “a solutions of lead (II) chloride…”PbCl2(aq)Acids are all aqueous
Rules for Writing Chemical Equations
Figure out which are reactants and which are products.Write chemical formulas for all substances, separated by theAdd state of matter to each substanceBalance equation
Chemical Equations Examples
Zinc and aqueous lead(II)nitrate are combined in an aqueous solution to produce zinc nitrate and a lead precipitate.zinc and lead(II)nitrate are reactants; zinc nitrate and lead are productsZn +Pb(NO3)2 Zn(NO3)2 +PbZn(s)+Pb(NO3)2(aq) Zn(NO3)2(aq)+Pb(s)Balance: coming right up!
Chemical Equation Examples
Carbon tetrachloride may be prepared by the reaction of natural gas, methane, and chlorine in the presence of ultraviolet light. Hydrochloric acid (HCl) is also a product of this reaction.methane and chlorine are the reactants; carbon tetrachloride and hydrochloric acid are the productsCH4 + Cl2 CCl4 +HClCH4(g) + Cl2(g) CCl4(s) +HCl(aq)To Balance
Balancing Chemical Equations
Big Idea: Law of Conservation of MatterMatter cannot be created or destroyedNumber of atoms of a certain element must be equal on reactant and product side.A balanced chemical equation shows the ratio of elements from one side to other
Rules for Balancing Equations
Write unbalanced equationOnce unbalanced equation is written, NEVER CHANGE THE SUBSCRIPTSOnly add coefficients to front of compoundCoefficients multiply everything in the compound by that amountWork with most complex molecule first, and save simplest for lastIf you have an odd # of elements on one side, multiply entireeqnby 2, and continue
Review: Reading Molecular Numbers
How many oxygen atoms?
O2H2OPO43-2H2SO42Ca(OH)23Ca3(PO4)2
2148424
Balancing Examples
O3 O2You need the same number of O’s on both sides2O3 3O26 = 6Balance: H2+ O2 H2O2H2+ O2 2H2OH’s : 4 O’s : 2
Relating to Types Chemical Reactions
Combustion of ethaneC2H6+ O2 CO2+ H2OWhich is most complex?Ethane – so balance those elements firstC2H6+ O2 2CO2+ 3H2ONow you have odd number of O’sMultiply entireeqnby 22(C2H6+ O2 2CO2+ 3H2O)2C2H6+ 2O2 4CO2+ 6H2OBalance O’s2C2H6+ 7O2 4CO2+ 6H2OMake a T chart to double check balance of all elements on both sides

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Chemical Equations - lhsblogs.typepad.com