1. Warmup 1/7/16 What does the term "precipitation" mean? What might this mean in chemistry? Objective Tonight’s Homework To define a precipitate and see a few examples Finish the worksheet from today

2. Notes on Precipitates We’re going to skip a couple chapters (as they contain mostly side stuff), but there’s one concept that we want to make sure we cover.

3. Notes on Precipitates We’re going to skip a couple chapters (as they contain mostly side stuff), but there’s one concept that we want to make sure we cover. Take a look at the following image: What appears to be happening here?

4. Notes on Precipitates We’re going to skip a couple chapters (as they contain mostly side stuff), but there’s one concept that we want to make sure we cover. Take a look at the following image: What appears to be happening here? Two liquids are being combined and something yellow is appearing. This yellow substance is a solid.

5. Notes on Precipitates When we mix two liquid chemicals and get a solid, we call that solid a precipitate. Given enough time, the solid will settle down to the bottom as seen here. If two substances stay liquid when combined, we say that the substances are soluble. They dissolve in water. Something that is insoluble is a precipitate or solid.

6. Notes on Precipitates So how do we show something like this as part of a chemical equation? Let’s look at an example: AgNO 3 (aq) + KCl (aq) → AgCl (s) + KNO 3 (aq)

7. Notes on Precipitates So how do we show something like this as part of a chemical equation? Let’s look at an example: AgNO 3 (aq) + KCl (aq) → AgCl (s) + KNO 3 (aq) Right away you’ll see something new. The letters in parenthesis after each chemical. These letters tell us what state the chemical is in. i.e. solid, dissolved, gas, etc. Chemicals can have the following codes: (s) - solid(l) – liquid(g) - gas (aq) – “aqueous”. This means dissolved in water, but can be solid if dried out

8. Notes on Precipitates How do we know if combining chemicals will yield a precipitate? There are a series of terrible rules to help you remember. (They have a lot of exceptions, sorry.)

9. Notes on Precipitates Solubility Rules: 1) Salts containing Li, Na, K, Cs, Rb are soluble. Salts containing the ammonium ion (NH 4 ) are also soluble. 2) Salts containing nitrate(NO 3 ) are generally soluble. 3) Salts containing Cl, Br, and I are generally soluble. Important exceptions to this rule are halide salts of Ag, Pb, and (Hg 2 ) 4) Most silver salts are insoluble. AgNO 3 and Ag(CH 3 COO) are exceptions 5) Most sulfate (SO 4 ) salts are soluble. Exceptions to this rule include BaSO 4, PbSO 4, Ag 2 SO 4 and SrSO 4 6) Except for rule 1, carbonates (CO 3 ), hydroxides (OH), oxides, silicates, and phosphates (PO 4 ) are insoluble 7) Sulfides (S # ) are insoluble except for calcium, barium, strontium, magnesium, sodium, potassium, and ammonium 8) Chromates (CrO 4 ), phosphates (PO 4 ), and fluorides (F) are frequently insoluble.

10. Precipitate Practice Those rules are somewhat of a handful. Let’s practice. CHEMICAL FORMULA NAMESOLUBLE? NH 4 CH 3 COO Ba(OH) 2 Iron (II) Carbonate NaOH RbNO 3 Cesium Sulfate MgSO 4 ZnCl 2 Zinc Hydroxide Zn 3 (PO 4 ) 2 AgBr KNO 3 CHEMICAL FORMULA NAME SOLUBLE? Al 2 S 3 Silver Acetate Sr 2 CrO 4 Aluminum Phosphate BaSO 4 Ca(OH) 2 BaCO 3 MgCrO 4 Iron (III) Sulfide NH 4 CN Silver Iodide Hg 2 SO 4 Lithium Chloride

11. Precipitate Practice Those rules are somewhat of a handful. Let’s practice. CHEMICAL FORMULA NAMESOLUBLE? NH 4 CH 3 COO Ammonium Acetate Y Ba(OH) 2 Barium Hydroxide N FeCO 3 Iron (II) Carbonate N NaOH Sodium Hydroxide Y RbNO 3 Rubidium NitrateY Cs 2 SO 4 Cesium SulfateY MgSO 4 Magnesium Sulfate Y ZnCl 2 Zinc ChlorideY Zn(OH) 2 Zinc HydroxideN Zn 3 (PO 4 ) 2 Zinc PhosphateN AgBrSilver BromideN KNO 3 P otassium Nitrate Y CHEMICAL FORMULA NAME SOLUBLE? Al 2 S 3 Aluminum Sulfide N AgCH 3 COOSilver AcetateY Sr 2 CrO 4 Strontium Chromate N AlPO 4 Aluminum Phosphate N BaSO 4 Barium SulfateN Ca(OH) 2 Calcium Hydroxide N BaCO 3 Barium Carbonate N MgCrO 4 Magnesium Chromate N Fe 2 S 3 Iron (III) SulfideN NH 4 CN Ammonium Cyanide Y AgISilver IodideN Hg 2 SO 4 Mercury SulfateY LiClLithium ChlorideY

12. Exit Question What is the precipitate in the following reaction? LiBr (aq) + AgNO 3 (aq)  LiNO 3 (?) + AgBr (?) a) LiNO 3 b) AgBr c) Both are precipitates d) Neither are precipitates