Double Displacement Reactions Experiment 10 General Form AY

Double Displacement Reactions Experiment 10

General Form AY + BZ AZ + BY • Where A and B are cations and Y and Z are anions • The anions swap places in double displacement reactions.

Lets look at some reactions • Aqueous solutions of calcium nitrate and sodium hydroxide are mixed together. A white precipitate is formed. Ca(NO 3)2(aq) + Na. OH(aq)

Solubility Rules • Alkali metals and NH 4+ compounds are soluble. • Nitrates(NO 3 ), acetates (CH 3 CO 2 ), chlorates (Cl. O 3 ), perchlorates(Cl. O 4 ), and sulfates(SO 4 2) are generally soluble (except for Sr+2, Ca+2, Ba+2, Pb+2, and Hg 2+2 sulfates). • Chlorides(Cl ), bromides(Br ), iodides(I ), are soluble (except for Silver(Ag+), mercury(I)(Hg 2+2), and lead(II)( Pb+2) halides). • Most compounds not included above are not soluble. – i. e. Sulfides(S 2), carbonates(CO 3 2), phosphates(PO 3), chromates(Cr. O 2), Oxides

Reaction Analysis • The reaction formed a precipitate. Is there an insoluble product? Calcium hydroxide is not a soluble substance. Ca(NO 3)2(aq) + 2 Na. OH(aq) Ca(OH)2 + 2 Na. NO 3

Lets look at some reactions • Aqueous solutions of phosphoric acid and potassium carbonate are mixed together. Bubbles begin to form. K 2 CO 3(aq) + H 3 PO 4(aq)

Evidence of reaction 1. Formation of a precipitate – Look formation of an insoluble substance. Refer to the solubility tables. 2. Formation of a gas – Look for H 2 CO 3, H 2 SO 3, or NH 4 OH • • • H 2 CO 3 H 2 O + CO 2 (g) H 2 SO 3 H 2 O + SO 2 (g) NH 4 OH H 2 O + NH 3 (g) 3. Formation of a slightly ionized substance • H 2 O, HC 2 H 3 O 2, H 3 PO 4, H 2 C 2 O 4, H 2 CO 3, H 2 SO 3, NH 4 OH, HF, CH 3 NH 2

Reaction Analysis • The reaction formed a gas. Is there a product that might form a gas? Carbonic acid will decompose to form water and carbon dioxide. 3 K 2 CO 3(aq) + 2 H 3 PO 4(aq) 2 K 3 PO 4 + 3 H 2 CO 3 Or 3 K 2 CO 3(aq) + 2 H 3 PO 4(aq) 2 K 3 PO 4 + 3 H 2 O + 3 CO 2

Lets look at some reactions • Aqueous solutions of oxalic acid and lithium hydroxide are mixed together. The test tube feels warm Li. OH(aq) + H 2 C 2 O 4(aq)

Reaction analysis • The reaction generated heat, so we look for the formation of a slightly ionized product. H 2 O, HC 2 H 3 O 2, H 3 PO 4, H 2 C 2 O 4, H 2 CO 3, H 2 SO 3, NH 4 OH, HF, CH 3 NH 2 2 Li. OH(aq) + H 2 C 2 O 4(aq) Li 2 C 2 O 4 + 2 HOH Water is a slightly ionized substance.

Lets look at some reactions • Aqueous solutions of potassium nitrate and cesium bromide are mixed together. No evidence of reaction is detected. KNO 3(aq) + Cs. Br(aq)

Reaction analysis • There was no visible evidence of reaction. Looking for indication of substances that would precipitate, form a gas, or a slightly ionized substance. KNO 3(aq) + Cs. Br(aq) no reaction

Evidence of reaction 1. Formation of a precipitate – Look formation of an insoluble substance. Refer to the solubility tables. 2. Formation of a gas – Look for H 2 CO 3, H 2 SO 3, or NH 4 OH • • • H 2 CO 3 H 2 O + CO 2 (g) H 2 SO 3 H 2 O + SO 2 (g) NH 4 OH H 2 O + NH 3 (g) 3. Formation of a slightly ionized substance • H 2 O, HC 2 H 3 O 2, H 3 PO 4, H 2 C 2 O 4, H 2 CO 3, H 2 SO 3, NH 4 OH, HF, CH 3 NH 2