Chemical Reaction Predictions

A brief review….

Types of Chemical Reactions Single Displacement Double Displacement Decomposition Synthesis Combustion

Single Displacement A +BC  AC + B One element shoves the other element out! Ex. Ca + AlCl3  CaCl2 + Al

Double Displacement AB + CD  AC + BD Elements switch partners ! Ex. Na3PO4 + BaCl2  Ba3(PO4)2 + NaCl

Decomposition AB  A + B Breaking chemical compound up, going from BIG to SMALL ! Ex. Au2O3  Au + O2

Synthesis A + B  AB Joining! Making new chemical compound ! Mg + N2  Mg3N2

Combustion HYDROCARBON (compound made up of just Cs and Hs) + O2  CO2 + H2O Chemical reactions involve a compound burning. Ex. C2H6 + O2  CO2 + H2O

Practice Zinc metal combines with hydrochloric acid (HCl). Sodium sulfide combines with magnesium oxide. Sodium metal combines with sulfur. Calcium oxide breaks down. C4H8 burns Gandalf combines aluminum metal with sodium hydroxide in solution. What does he produce?]

Aqueous Solutions Compounds dissolved into water. Can contain molecules or ions in a solution. How do you distinguish between ion or molecule?

DISSOCIATION !! The ability of a compound to breakdown in a solution into individual ions Ionic Compounds Break down into cations and anions Electrical conductors—ions flow through solution Molecular Compound Compound remains intact as “molecules,” no breakdown Generally NOT electrical conductors

Dissociation Reactions NaCl CaCl2

Nonelectrolyte NO dissociation of the compound into anions and cations Compound remains in its molecular form when dissolved in a solution No conduction of electricity Ex. Pure water, molecular compounds, organic compounds

Electrolytes Compound dissolved in a solution that breaks down into cations and anions. Dissociates into enough ions to conduct electricity. Strong vs. weak—dependent on the amount of ions in the solution

Strong Electrolyte LOTS of ions present in solution Light bulb burns brightly ! Complete dissociation of the compound into ions Good electrical conductor Ex. NaCl, all soluble ionic compounds, very few molecular compounds

Weak Electrolyte Compound is at a crossroads part dissociates into ions—partial ionization part still exists in the molecular form Some electrical conduction but poor Dimly lit light bulb Ex. Acetic acid, carboxylic acid/amines

What is the concentration ([ ]) of a particular ion in solution? Sometimes [ion] = [compound], but not always An ion can have only ONE concentration in a solution May have multiple sources for one ion. What do you do then? (add them up)

Example 1: Hercules has obtained an aqueous solution of 0.00384 M Na2SO4 and 0.00202 M NaCl. What is the concentration (in molarity) of each ion present in the solution? Total ion concentration? [Na+] = 0.00970 M [Cl-] = 0.00202 M [SO4-2] = 0.00384 M Total ion concentration = 0.01556 M

Example 2: Oral Rehydration Therapy (ORT) is an electrolyte solution containing 3.5 g NaCl, 1.5 g KCl, 2.9 g sodium citrate (Na3C6H5O7) and 20.0 g glucose (C6H12O6) in 1 liter. What is the molarity of each ion/molecule in a solution of ORT? Hint: sodium citrate is a strong electrolyte, glucose is a nonelectrolyte [Na+] = 0.093 M [K+] = 0.020 M [Cl-] = 0.080 M [C6H5O7-3] = 0.011 M

Solubility How much solute dissolves in a solution to produce a saturated solution Temperature and Pressure dependent Increase with increasing temperature Increases with decreasing temperature (ex. Water in lake) Pressure increases, solubility increases (ex. Soda can) TEMPERATURE: Solubility increase with increasing temperature—applies for most substances, good for liquids Solubility increases with decreasing temperature—applies to gases (talk about how this applies to aquatic life—eutrophic vs. anoxic conditions with oxygen in water supporting organisms) PRESSURE: -not a big influence for solids/liquids -huge influence on gases -increased solubility of gas when partial pressure increases in area above solution (p. 476) **Soft Drinks**--gas escapes from soda as pressure decreases and causes solubility to decrease

Particles move back and forth from being dissolved to leaving a solution—equilibrium is reached when this movement is balanced. A point is reached where adding more solute to a solution will prevent the solute from dissolving in the solution. Dump a lot of salt into a beaker of water. Have a student continue to stir the solution as much as they can…tell them every salt particle has to dissolve.

Types of Solutions 1) Saturated Maximum amount of solute that can be dissolved in a solvent Certain temperature and pressure 2) Unsaturated Solution with LESS solute than the maximum solute amount at a certain temperature and pressure More solute can be added and dissolved in the solution 3) Supersaturated Contains MORE solute than the maximum solute amount At saturated point, any more solute added will fall out of solution…cannot be dissolved. Saturated solutions are at equilibrium—bath tub is filled to the brim with water, any more would cause overflow and any less would decrease the amount. Think of tea—ask students about what they consider supersaturated/unsaturated/saturated tea.

Solubility Diagrams

How much sugar is dissolved at 50 degrees Celcius? Salt?

Same as with the simple one just have to look at one line for the correct chemical compounds. NH4Cl—how much is dissolved at 50 degrees Celcius? NaCl?

Solubility Rules How do we determine which compounds will dissolve in water or not? Based on data, patterns have been observed and helped develop the rules we follow Look in your reference packet!!!!

Which compounds are soluble in water Which compounds are soluble in water? 1) BaCl2 2) Pb (NO3)2 3) Na2S 4) BaCO3 5) PbS Soluble Insoluble

Your Turn……. NaCl KBr KNO3 p. 73 of Merrill textbook Teacher’s Ed.

Homework Read pp. 125-129, 136-137 Problems p. 160 # 25, 29, 31, 53, 57 Read pp. 1-3 of Reaction Type handout and make notes Finish solubility worksheet

AP Question Snow White conducts a complete combustion of a hydrocarbon with excess oxygen. This combustion produces equimolar quantities of carbon dioxide and water. What is a possible molecular formula for the compound? A) C2H2 B) C2H6 C) C4H8 D) C6H6 C