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Chem I Mon, Nov 15 th, 2010 Return Daily Quiz & Grade in Class Lab Tomorrow, Weds, Fri-Long Pants and Closed Toed Shoes Quiz on Thursday WebAssign Due Thursday Test of Monday Visitor Tomorrow
Chem I Tues, Nov 16 th, 2010 Lab Weds & Fri-Long Pants and Closed Toed Shoes Quiz on Thursday-Review PPTS. WebAssign Due Thursday at 11:59 pm Test of Monday
Double-Replacement Reactions What will I see? …Predicting Products
Double-Replacement Reactions when 2 aqueous ionic compounds exchange ions AX + BY AY + BX What are the metals? What are the nonmetals? A & B X & Y
Steps for predicting products: Write the components of the reactants in a skeleton equation Al(NO 3 ) 3 + H 2 SO 4 Identify the cations & anions in each compound Al(NO 3 ) 3 has Al +3 and NO 3 - H 2 SO 4 has H + and SO 4 -2 Pair up each cation with the anion from the other compound Al +3 pairs with SO 4 -2 H + pairs with NO 3 -
Steps for predicting products: Write the formulas for the products using the pairs from previous step Write the complete equation for the double- replacement reaction Balance the equation Al +3 SO 4 -2 Al 2 (SO 4 ) 3 Al(NO 3 ) 3 + H 2 SO 4 H+H+ NO 3 - HNO 3 Al 2 (SO 4 ) 3 +HNO 3 236
Lets practice… Aqueous lithium iodide and aqueous copper (II) nitrate react to produce what? What is the formula for lithium iodide & copper (II) nitrate? Li + I-I- LiI Cu +2 NO 3 - Cu(NO 3 ) 2
Steps for predicting products: Write the components of the reactants in a skeleton equation LiI + Cu(NO 3 ) 2 Identify the cations & anions in each compound LiI has Li + and I - Cu(NO 3 ) 2 has Cu +2 and NO 3 - Pair up each cation with the anion from the other compound Li + pairs with NO 3 - Cu +2 pairs with I -
Steps for predicting products: Write the formulas for the products using the pairs from previous step Write the complete equation for the double- replacement reaction Balance the equation Li + NO 3 - Li NO 3 Cu +2 I - Cu I2I2 LiI + Cu(NO 3 ) 2 LiNO 3 +CuI 2 22
What do we mean when we say something is soluble? Is salt soluble in water? Yes Is a sugar cube soluble in water? Yes Is iron (ex. a nail) soluble in water? No
Will the products be soluble or precipitate out? Look at the solubility table on the back of your periodic table For each compound formed: 1. first look up the anion on the table 2. select the cation category 3. if the compound formed is insoluble it will precipitate: label (s) after the formula 4. if soluble label (aq) after the formula
Solubility Rules 1. Compounds containing Group I ions and ammonium are soluble. 2. Nitrates, acetates and chlorates are soluble. 3. Chlorides, bromides and iodides are soluble except with lead, silver, copper(II), and mercury ions. Fluorides are soluble except with Group II and lead ions. 4. Sulfates are soluble except those containing barium, strontium, calcium, lead and silver ions. 5. Carbonates, chromates, phosphates, hydroxides are insoluble except with those cations in rule Sulfides are insoluble except for calcium, barium, strontium, magnesium, sodium, potassium, and ammonium ions.
What will you see? For the first product: What is the anion in LiNO 3 ? NO 3 - nitrate What is the cation? Li + lithium Is the anion/cation combination soluble or insoluble? soluble = (aq)
What will you see? For the second product: What is the anion in CuI 2 ? What is the cation? Is the anion/cation combination soluble or insoluble? I - iodide Cu +2 copper (II) not soluble = (s)
Write the balanced equation with descriptors: (s) (l) (g) or (aq) Reminder: All reactants are aqueous. LiI + Cu(NO 3 ) 2 LiNO 3 +CuI 2 22 (aq) (s)
Solubility Rules Solubility Rules are used to give us a general idea of whether or not an ionic compound will dissolve in water to form an aqueous solution These are very useful in determining states of matter for your compounds in reactions, especially double replacement precipitation reactions.
What Solubility Rules Mean Solubility Rules give you general guidelines based on cations and anions present in an ionic compound. For each compound you have in the presence of water, look for a rule that will describe it.
How to use the Solubility Rules If the compound is insoluble in water, it will not dissolve and will fall out as a solid precipitate. If the compound is soluble in water, it will dissolve and form an aqueous solution.
General Solubility Rules 1. Most nitrate salts are soluble. 2. Most salts of Na +, K +, and NH 4 + are soluble. 3. Most chloride salts are soluble; notable exceptions are Ag +, Pb 2+, and Hg Most sulfate salts are soluble; notable exceptions are Ba 2+, Pb 2+, and Ca Most hydroxide compounds are mostly insoluble; the important exceptions are Na + and K + and Ba 2+ and Ca 2+ are mostly soluble. 6. Most sulfide, carbonate, and phosphate salts are mostly insoluble except Na +, K +, and NH Most dichromate salts are soluble except Ag + and Pb +2. * insoluble compounds will fall out of solutions as precipitates