Chapter 10 Chemical Reactions

Must Know Diatomic molecules – H 2 – N 2 – O 2 – F 2 – Cl 2 – Br 2 – I 2 Common Allotropes – P 4 – S 8

State of Element or Compound Aqueous – (aq) – Dissolved in water Solid – (s) Gas – (g) Liquid – (l)

Writing Chemical Equations You will have word problems that you must write the skeleton equation for. – Be able to write formulas for ionic compounds, covalent compounds, acids, and bases. You should know how to balance equations Must be organized Do it exactly how I do it

Examples ___KClO 3  ___KCl + ___O 2 Pg 282 #4 - 6

Types of Chemical Reactions Synthesis reactions – A + B  AB – 2K + Br 2  2KBr Decomposition Reactions – AB  A + B – Ni(OH) 2  NiO + H 2 O

Combustion Reactions – Always contains oxygen – Oxygen combines with another substance to release huge amounts of energy and/or light – Usually have to put energy in in order to initiate the reaction. Get huge gains of energy out of the reaction. – Usually occurs with a hydrocarbon. C x H y Gasoline is a hydrocarbon – When a hydrocarbon is completely combusted your products will always be CO 2 + H 2 O. Example: __C 2 H 6 + __O 2  __CO 2 + __H 2 O You balance

Replacement Reactions – 2 Types 1.Single Replacement Reactions – A + CB  AB + C – Determined by reactivity Use the reactivity chart If element A is more reactive than element C then the reaction will occur. If it is not then N.R. – __K + __ZnCl 2  __KCl + __Zn (You balance)

Single Replacement Reactions Practice Determine if the reaction will occur and balance the equations. RbI (aq) + F 2(g)  Fe + Na 3 PO 4 

Double Replacement Reactions – AB + CD  AD + CB – 2NaOH + CuCl 2  2NaCl + Cu(OH) 2 – Double Replacement Reactions forms A solid (precipitate) A liquid (H 2 O) A gas

Prediction Sheet Examples 1)CaCO 3  CaO + CO 2 2)2Na + 2H 2 O  2NaOH + H 2 3)SrO + H 2 O  Sr(OH) 2 4)Ba(OH) 2  BaO + H 2 O 5)2KClO 3  2KCl + 3O 2 6)C 6 H 8 + 8O 2  6CO 2 + 4H 2 O

Terminology to Know Soluble – Dissolves in a solution Dissociate – Comes apart

Rules for forming a precipitate in double replacement reactions Solubility rules – Strong acids dissociate in water – HCl, HBr, HI, H 2 SO 4, HNO 3, HClO 4, HClO 3 – Example: HClO 3  H + and ClO 3 - – Strong bases dissociate in water – LiOH, NaOH, KOH, RbOH, CsOH – Example: LiOH  Li + and OH -

Soluble Salt Rules – Ionic compounds (metal/nonmetal) -Soluble salts dissociate

Soluble Salt Rules Always soluble in a cpd. 1)Group 1 metals, NH 4, NO 3, ClO 4, ClO 3, C 2 H 3 O 2 2)Cl -, Br -, I - 3)SO 4 2- Exceptions 1)None 2)Ag, Pb, Hg )Ag, Pb, Hg 2 2+, Ca, Sr, Ba

If the salt falls under one of the exceptions then it is insoluble and forms a precipitate. Examples – NaCl – Rule 1. Soluble. – Fe(C 2 H 3 O 2 ) 2 – Rule 1. Soluble. – ZnCl 2 – Rule 2. Soluble. – AgBr – Rule 2. Insoluble (forms precipitate) – MgSO 4 – Rule 3. Soluble. – CaSO 4 – Rule 3. Insoluble (forms precipitate)

Remember that in a double replacement reaction 1 of 3 things must form or the reaction does not occur. At this point we have only looked at formation of precipitates. Pg. 294 #33 – Will this happen? – Write the balanced chemical equation, complete ionic equation, and net ionic equation. You will be required to write all 3.

D.R.R. Practice Problems (precipitate)) Determine if the reaction will occur. If the reaction occurs write the balanced chemical equation, complete ionic equation, and the net ionic equation. Aqueous solutions of ammonium phosphate and sodium sulfate are mixed. Aqueous solutions of lithium sulfate and calcium nitrate are mixed.

Acid Base Reactions Water forming 1 of the 3 things that must happen in a double replacement reaction. HCl (aq) + KOH (aq)  H 2 O (l) + KCl (aq) Write the complete ionic equation and net ionic equation. Diprodic reactions – Contains 2 hydrogen; also water forming – H 2 SO 4(aq) + 2KOH (aq)  2H 2 O (l) + K 2 SO 4(aq)

Acid Base Reactions Practice Problem (liquid) Pg. 296 # 40

Production of gases Final result used to determine double replacement reactions – Acid + carbonate (CO 3 2- )  CO 2(g) + H 2 O + ions – Acid + cyanide (CN - )  HCN (g) + ions – Acid + sulfide (S 2- )  H 2 S (g) + ions Example: – 2HClO 4(aq) + K 2 CO 3(aq)  CO 2(g) + H 2 O (l) + 2KClO 4(aq)

D.R.R. Practice Problems (gas) Pg. 299 # 44

Homework Pg