Chem IMon, Nov 15th, 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 ITues, Nov 16th, 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(NO3)3 + H2SO4

Identify the cations & anions in each compound

Al(NO3)3 has Al+3 and NO3-

H2SO4 has H+ and SO4-2

Pair up each cation with the anion from the other compound

Al+3 pairs with SO4-2

H+ pairs with NO3-

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 SO4-2 Al2

(SO4)3

Al(NO3)3 + H2SO4

H+ NO3- HNO3

Al2 (SO4)3 + HNO32 3 6

Let’s 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- LiI

Cu+2 NO3- Cu(NO3)2

Steps for predicting products: Write the components of the reactants in a

skeleton equation

LiI + Cu(NO3)2

Identify the cations & anions in each compound

LiI has Li+ and I-

Cu(NO3)2 has Cu+2 and NO3-

Pair up each cation with the anion from the other compound

Li+ pairs with NO3-

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+ NO3- Li NO3

Cu+2 I- CuI2

LiI + Cu(NO3)2 LiNO3 + CuI22 2

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 Rules1. 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 1.6. 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 LiNO3?

NO3- 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 CuI2?

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(NO3)2 LiNO3 + CuI22 2(aq) (aq) (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 NH4

+ are soluble.

3. Most chloride salts are soluble; notable exceptions are Ag+, Pb2+, and Hg2

2+.

4. Most sulfate salts are soluble; notable exceptions are Ba2+, Pb2+, and Ca2+.

5. Most hydroxide compounds are mostly insoluble; the important exceptions are Na+ and K+ and Ba2+ and Ca2+ are mostly soluble.

6. Most sulfide, carbonate, and phosphate salts are mostly insoluble except Na+, K+, and NH4

+.

7. Most dichromate salts are soluble except Ag+ and Pb+2. 

* insoluble compounds will fall out of solutions as precipitates