Double Replacement Reactions (p.7-8 in your notes) In a double replacement reaction, both reactants are ionic compounds, and in the course of the reaction the cations and anions trade partners. The generic equation for this is: AX + BY  AY + BX

Please find Table E in your Data Book Notice there are two parts to Table E, we will be using both the top and bottom tables. On the top table, where are the cations? Where are the anions? On the top table, find one cation that always makes soluble compounds. Note! Hydrogen as a cation makes compounds soluble! Find one anion that always makes soluble compounds. Find one anion that often makes insoluble compounds. What is one compound that is slightly soluble? How do you think slightly soluble compares to soluble?

Double Replacement Reactions (p.7-8 in your notes) Double Replacement reactions occur in solution (there is water around). Think about what you know about how aqueous compounds behave (what are the ions doing?). How does this allow a reaction to occur? For a Double Replacement reaction to occur, this first condition MUST be met… Both of the reactants are soluble in water (aq)! … AND …

… AND one of these statements is true.  A precipitate (new solid) is formed. This will be a compound that is not soluble (or only slightly soluble). It will look foggy/cloudy. A gas or new covalent compound is produced (CO2, H2, H2O, etc). Heat or light is produced.

A note about bubbles and H2CO3… Find the note about H2CO3 on p.7 in your notes. What is really produced if you predict H2CO3 as a product? What would you call the process by which H2CO3 becomes H2O and CO2? What would you see in a reaction like this?

Notice! Insoluble things are SOLID = (s) Try one! AgNO3 (___) + NaCl (__) AgCl (__)+ NaNO3 (___) Use Table E to determine the state of matter for each compound (assume there is water around – if something is soluble, it is aqueous). AgNO3 (aq) + NaCl (aq)  AgCl (s) + NaNO3 (aq) Are both reactants soluble? YES Is one of the products a solid, liquid, or gas? YES The reaction happens! Notice! Insoluble things are SOLID = (s)

Try one! 3KOH (__) + Al(NO3)3 (___)  3KNO3 (__)+ Al(OH)3 (___) Use Table E to determine the state of matter for each compound (assume there is water around – if something is soluble, it is aqueous). Are both reactants soluble? Is one of the products a solid, liquid, or gas? Does the reaction happen?

Predicting Products If you are only given the reactants, you have to predict the products. Trade partners to create two new real, neutral compounds. Potassium chromate is mixed with iron (II) nitrate. K2CrO4 (__) + Fe(NO3)2 (__)  K2CrO4 (__) + Fe(NO3)2 (__)  KNO3 (__) + FeCrO4 (__) Balance the reaction, then decide if the reaction happened (Are both reactants soluble? Is one of the products a solid, liquid or gas?) K2CrO4 (aq) + Fe(NO3)2 (aq)  2KNO3 (aq) + FeCrO4 (s)