Chemical Reactions Chapter 11
How to Make a Cake 1. Add flour and eggs and milk, put in the oven for 20 minutes at 450oF and you will have yourself a cake. 2. Flour(s) + eggs(s) + milk(l) → cake(s)
Word Equation: uses names of the reactants and products. Ex:aluminum plus copper (II) chloride yields aluminum chloride and copper REPLACE THE PLUS WITH A (+) AND THE YIELD WITH AN () ALUMINUM + COPPER (II) CHLORIDE ALUMINUM CHLORIDE AND COPPER • Skeleton Equation: uses chemical symbols with no relative amounts. Ex: Al(s) + CuCl2(aq) → AlCl3(aq) + Cu(s)
NOTE!!!!!!! • Make sure compounds are written properly. • Remember to put up the charges and use criss-cross method if needed. • *** Remember the diatomic molecules.
3. Phases: s - solid phase l - liquid phase g - gaseous phase aq – aqueous phase (exists in a water solution) EX: NaCl(aq) = solid NaCl dissolved in H2O
NOTE!!!!!!! • Balanced Formula Equation: shows the relative amounts of the atoms on each side of the equation. EX: 2Al(s) + 3CuCl2(aq)→ 2AlCl3(aq) + 3Cu(s) LAW OF CONSERVATION OF MATTER • To balance equations use ONLY coefficients. • NEVER, NEVER change a subscript
Types of Reactions • Combination (Synthesis) • Decomposition • Single Replacement • Double Replacement • Combustion
1. Combination (Synthesis): Ex: A + B → AB Ex: 2H2 + O2 → 2H2O 2. Decomposition: Ex: AB → A + B Ex: 2H2O → 2H2 + O2 (electrolysis)
3. Single Replacement: Ex: A + BC → C + BA Ex: Zn + Cu(NO3)2 → ? Like replaces likeUSE ACTIVITY SERIES Is Zn higher than Cu on the list?
Activity Series of Metals Decreasing Activity Use for single replacement Reactions Li K Ba Sr Ca Na Mg Al MnZn Zn + Cu(NO3)2 → Zn(NO3)2 + Cu Fe Cd Co Ni Sn Pb HCu Ag Hg Au
4. Double Replacement: Ex: AB + CD → AD + CB Ex: HCl + NaOH → H(OH) + NaCl 5. Combustion: Ex: hydrocarbon + O2 → CO2 + H2O Ex: CH4 + 2O2 → CO2 + 2H2O This is an example of complete combustion.
Ionic Equations • These beakers contain 0.1 M solutions of silver nitrate, AgNO3, and iron (III) chloride, FeCl3. Since we can not see solid particles in these beakers we conclude that silver nitrate and iron (III) chloride are soluble in water. • Let's check the conductivity of these solutions to be sure these salts form ions when they dissolve in water. AgNO3 FeCl3
To test for ions we will dip the two wires into a solution. If ions are present, the solution will conduct electricity and the bulb will light.
The wires that complete the electrical circuit to the light bulb have been dipped into a solution of FeCl3. Does FeCl3 form ions when it dissolves in water? YES NO
The wires that complete the electrical circuit to the light bulb have been dipped into a solution of FeCl3. Right, when FeCl3 dissolves in water it forms Fe+3 and Cl-1 ions. Next let's test silver nitrate.
The wires that complete the electrical circuit to the light bulb have been dipped into a solution of AgNO3. Does AgNO3 form ions when it dissolves in water? YES NO
The wires that complete the electrical circuit to the light bulb have been dipped into a solution of AgNO3. Right, when AgNO3 dissolves in water it forms Ag+1 and NO3-1 ions.
The conductivity experiments established that silver nitrate and iron (III) chloride form ions in aqueous solution. • The ions conduct electricity so the bulb lights.
Let's mix the solution of AgNO3 with the solution of FeCl3. Mixing yields a white precipitate and a brown solution. What precipitated?
This is a double replacement rxn Either AgCl or Fe(NO3)3 formed the ppt See Table 11.3 on page 344
Fe(NO3)3 -Nitrate salts are soluble (dissolve and therefore don’t form precipitates) AgCl -THIS IS THE PPT
We now know the phases: AgNO3(aq) + FeCl3(aq)→ AgCl(s) + Fe(NO3 )3(aq) Let's look at the ions formed in the solutions. Not every ion formed is directly involved in the reaction.
We mixed a solution that contained Fe+3 and Cl-1 ions with one that contained Ag+1 and NO3- ions.
AgNO3(aq) + FeCl3(aq)→ AgCl(s) + Fe(NO3 )3(aq) The Ag+1 and Cl-1 ions reacted to form the ppt, AgCl Are Fe3+ & NO-3 directly Involved in the formation of AgCl?
Net Ionic Equations • Shows what happens to the ions that take part in chemical reactions. • Shows dissolved ionic compounds as their free ions. AgNO3(aq) + FeCl3(aq)→ AgCl(s) + Fe(NO3 )3(aq) 1st BALANCE THE EQUATION: 3AgNO3(aq)+FeCl3(aq)→ 3AgCl(s)+Fe(NO3 )3(aq)
3AgNO3(aq)+FeCl3(aq)→ 3AgCl(s)+Fe(NO3 )3(aq) 2nd WRITE THE IONIC EQUATION: Only for aqueous solutions 3Ag+ +3NO3- + Fe+3 +3Cl-→3AgCl(s)+Fe+3+3NO3-
3rd CANCEL OUT THE SPECTATOR IONS: • Ions that undergo no chemical change & aren’t directly involved during a chemical reaction. • Appear on both sides of the chemical reaction. 3Ag+ +3NO3- + Fe+3 +3Cl-→3AgCl(s)+Fe+3+3NO3- Cancel out all spectator ions
4th WRITE THE NET IONIC EQUATION: Rewrite equation leaving out spectator ions. 3Ag+ +3NO3- + Fe+3 +3Cl-→3AgCl(s)+Fe+3+3NO3- 3Ag+(aq) + 3Cl-(aq)→3AgCl(s) Reduce coefficients Ag+(aq) + Cl-(aq)→AgCl(s) So, Fe+3 &NO3-1 weren’t directly involved in the formation of AgCl.
EX: Cl2(g) + NaBr(aq) → Br2(l) + NaCl(aq) 1st: write ionic eq Cl2(g) + Na+ + Br -→ Br2(l) + Na+ + Cl – 2nd: cancel out spectator ions Cl2(g) + Na+ + Br -→ Br2(l) + Na+ + Cl – 3rd: write net ionic eq Cl2(g) + Br -→ Br2(l) + Cl – 4th: balance final net ionic eq Cl2(g) + 2Br -→ Br2(l) + 2Cl –
Practice on Your Own Do question #32 a On page 344