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Chemical Equations

Chemical Equations. Things you should already know…. Elements from the periodic table Your polyatomic ions The BrINClHOF’s How to write ionic and covalent compounds names The symbols for solid, liquid, gas, and aqueous How to interpret word problems. Other Things to Know.

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Chemical Equations

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  1. Chemical Equations

  2. Things you should already know… • Elements from the periodic table • Your polyatomic ions • The BrINClHOF’s • How to write ionic and covalent compounds names • The symbols for solid, liquid, gas, and aqueous • How to interpret word problems

  3. Other Things to Know • When metals 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 added • Ex. “hydrogen is bubbled into a solution of…” • Is written as: H2(g) + …  …

  4. More Things You Should Know • Solutions are all aqueous (aq) • Ex: “a solutions of lead (II) chloride…” • PbCl2 (aq) • Acids are all aqueous

  5. 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 substance • Balance equation

  6. 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 products • Zn + Pb(NO3)2  Zn(NO3)2 + Pb • Zn(s) + Pb(NO3)2(aq) Zn(NO3)2(aq) + Pb(s) • Balance: coming right up!

  7. 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 products • CH4 + Cl2  CCl4 + HCl • CH4(g) + Cl2(g)  CCl4(s) + HCl(aq) • To Balance

  8. Balancing Chemical Equations • Big Idea: Law of Conservation of Matter • Matter cannot be created or destroyed • Number 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

  9. Rules for Balancing Equations • Write unbalanced equation • Once unbalanced equation is written, NEVER CHANGE THE SUBSCRIPTS • Only add coefficients to front of compound • Coefficients multiply everything in the compound by that amount • Work with most complex molecule first, and save simplest for last • If you have an odd # of elements on one side, multiply entire eqn by 2, and continue

  10. Review: Reading Molecular Numbers How many oxygen atoms? 2 1 4 8 4 24 • O2 • H2O • PO43- • 2H2SO4 • 2Ca(OH)2 • 3Ca3(PO4)2

  11. Balancing Examples • O3  O2 • You need the same number of O’s on both sides • 2O3  3O2 • 6 = 6 • Balance: H2 + O2  H2O • 2H2 + O2  2H2O • H’s : 4 O’s : 2

  12. Relating to Types Chemical Reactions • Combustion of ethane • C2H6 + O2 CO2 + H2O • Which is most complex? • Ethane – so balance those elements first • C2H6 + O2 2CO2 + 3H2O • Now you have odd number of O’s • Multiply entire eqn by 2 • 2(C2H6 + O2 2CO2 + 3H2O) • 2C2H6 + 2O2 4CO2 + 6H2O • Balance O’s • 2C2H6 + 7O2 4CO2 + 6H2O • Make a T chart to double check balance of all elements on both sides

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