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Steps for Balancing Equations 1.Write the skeleton equation Use arrows, +/- & physical states of matter 2. Count the atoms of the reactants 3. Count the.

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Presentation on theme: "Steps for Balancing Equations 1.Write the skeleton equation Use arrows, +/- & physical states of matter 2. Count the atoms of the reactants 3. Count the."— Presentation transcript:

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2 Steps for Balancing Equations 1.Write the skeleton equation Use arrows, +/- & physical states of matter 2. Count the atoms of the reactants 3. Count the atoms of the products 4. Change the coefficients to make the number of atoms of each element equal on both sides of the equation 5. Write the coefficients in their lowest possible ratio NEVER, NEVER CHANGE THE SUBSCRIPT

3 Count the reactants & products Balance the H & O atoms with coefficients for the reactants to = the products

4 Add the physical states of the elements Now you have a happy equation

5 A chemical reaction in which 2 or more reactants produce 1 product General form A + B AB In the cartoon, the skinny bird (reactant) and the worm (reactant) combine to make one product, a fat bird.

6 Examples -2Na + Cl 2 2NaCL - 2Mg + O 2 2MgO - 4Al + 3O 2 2Al 2 O 3 - H SO 3 H 2 SO 4 (this is one cause of acid rain) - H 2 0 +CO 2 H 2 CO 3 (this is why rainwater is naturally acidic) - H 2 O + MgO Mg(OH) 2

7 Special CASE Scenarios for these RXNs Metallic oxide + Water Base Na 2 O + H 2 O 2NaOH Non-Metallic oxide + Water Acid SO 3 + H 2 O H 2 SO 4

8 Special CASE Scenarios for these RXNs Metallic oxide + CO 2 Metal carbonate Metal chloride + Oxygen Metal chlorate CaO + CO 2 CaCO 3 2KCl + 3O 2 2KClO 3

9 A chemical reaction where 1 compound, breaks apart into 2 or more simpler products General form AB A + B In this cartoon the egg (the reactant), which contained the turtle at one time, now has opened and the turtle (product) and egg shell (product) are now two separate substances.

10 Examples - 2 H 2 O 2H 2 + O 2 - 2HgO 2Hg + O 2 - 2Ag 2 O 4Ag + O 2 - CaCO 3 CaO + CO 2 - H 2 CO 3 H 2 O + CO 2 - Decomposition reactions often require an energy source: Heat Light Electricity

11 Special CASE Scenarios for these RXNs Heating an acid non metallic oxide + water Heating a carbonate oxide + CO 2 Heating a base metallic oxide + water Heating a metal chlorate chloride + O 2 Heating a metallic oxide Metal + O 2 These are just the reverse of their synthesis RXNs Heating a sulfite Metal oxide + SO 2

12 A reaction in which atoms of one element replace the atoms of another element that is part of a compound Notice, the guy in the orange shirt steals the date of the other guy. So, a part of one of the reactants trades places and is in a different place among the products

13 2. Anions replace Anions 1. Cations replace Cations General Form AB + C CB + A C would be the cation/metal and so replaced A, which would have to be a cation General Form DE + F DF + E F would be the anion/non-metal and so replaced E, which would have to be a anion

14 Examples: a.Cu + AgNO 3 Cu(NO 3 ) 2 + Ag Cation replaces Cation b.NaI + Cl 2 NaCl + I 2 Anion replaces Anion

15 Special situations for SR RXNs 1. Activity Series Definition A list of metal/cations in order of decreasing reactivity Used to determine if one metal can replace another in a RXN The higher its position on chart the more metals it can replace Ex: sodium will replace aluminum The lower its position on the chart the less metals it can replace Ex: zinc will not replace magnesium

16 3.Halogens The halogens also have a series; As you go down group 17 they decrease in reactivity Ex: Chlorine cannot replace fluorine but it can replace bromine Special situations for SR RXNs 2.Water for writing RXNs it may be useful to write water as H(OH). Why?

17 Special situations for SR RXNs Do the following reactions occur? Explain. Zn + H 2 SO 4 H 2 + ZnSO 4 Sn + 2NaNO 3 Sn(NO 3 ) 2 + 2Na 2NaCl + F 2 2NaF + Cl 2 CaCl 2 + I 2 CaI 2 + Cl 2

18 A reaction where there is an exchange of cations between 2 ionic compounds Notice how the first guy exchanged hats with the second guy, so they are both wearing each other's hat.

19 General Form AB + CD AD + CB ** Make sure of cation and anion placement Ex: BaCl 2 + K 2 CO 3 BaCO 3 + 2KCl 3KOH + H 3 PO 4 3H(OH) + K 3 PO 4

20 Driving Forces in double replacement RXNs One of three things must form for these RXNs to occur 1. A molecular compound like water forms 2.A gas forms that bubbles out i.e. (H 2, CO 2, H 2 S, CO, etc.) 3. A precipitate forms Driving Forces allow a RXN to take place Use your net ionic equation to see if one of the following are formed

21 How do you know if something is a precipitate? 1. It is insoluble or slightly soluble in water 2. Check your solubility chart Examples: will these RXNs occur? Explain BaCl 2 AgCl Ca 3 (PO 4 ) 2 NaNO 3 Soluble….NR Insoluble….Yes Soluble….NR

22 Examples: will these RXNs occur? FeS (s) + HCl (aq) FeCl 2(aq) + H 2 S Pb(NO 3 ) 2 (aq) + 2KI (aq) 2KNO 3 (aq) + PbI 2 FeCl 3 (aq) + Al(NO 3 ) 3 (aq) Fe(NO 3 ) 3 (aq) + AlCl 3 (aq) Yes No…soluble … no driving force present

23 Definition: Oxygen reacts with another substance often producing energy in the form of heat and light Types: 1. Complete combustion Hydrocarbons combine with oxygen to produce carbon dioxide and water Definition: If sufficient oxygen is present to burn completely General form: C x H y + O 2 CO 2 + H 2 O

24 Definition: 2. Incomplete combustion Insufficient oxygen is present to burn completely Hydrocarbons combine with oxygen to produce poisonous carbon monoxide and solid elemental carbon as well as carbon dioxide and water Examples:

25 Extra Special RXNs Reactive metals and water (SR) Group 1 and 2 metals react to form a metal hydroxide and hydrogen gas Acid and a Base React to form a salt (ionic compound composed of the anion of the acid and the cation of the base) and water

26 Aqueous SLN When two (aq) solutions that contain ions as solutes combine…. The ions may react with one another The H 2 0 molecules dont usually react The three types of products can form aka driving forces …. Gas, water, or precip Chemical equations do not always show all that happens in a RXN

27 Solutions are composed of Solute Solvent Aqueous SLN Is a sln in which the solvent is water Net Ionic Equations

28 Substances that are ions in a solution and are written as such These equations show all of the particles in a solution as they really exist Some ions are in both the RXT & PROD, these are called… SPECTATOR IONS

29 Net Ionic Equations SPECTATOR IONS - dissociation only occurs if it is in an aqueous solution S, L, G are not ions see your solubility chart

30 Net Ionic Equations Regular equation 2NaOH (aq) + CuCl 2 (aq) 2NaCl (aq) + Cu(OH) 2 (s) Ionic equation 2Na + (aq) + 2OH - (aq) + Cu +2 (aq) + 2Cl - (aq) 2Na + (aq) + 2Cl - (aq) + Cu(OH) 2 (s)

31 Net Ionic Equations Net Ionic equation 2OH - (aq) + Cu +2 (aq) Cu(OH) 2 (s) Net ionic equation is formed when all of the spectator ions are cancelled


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