Double Displacement Chemical Reactions PDF

Double Displacement Reactions Objectives for today: ◻ What is a double displacement reaction ◻ Predict the solubility of a product and if precipitate is formed using solubility information ◻ Predict weather a reaction occurs ◻ Write a complete balanced equa...

Double Displacement Reactions Objectives for today: ◻ What is a double displacement reaction ◻ Predict the solubility of a product and if precipitate is formed using solubility information ◻ Predict weather a reaction occurs ◻ Write a complete balanced equation for a double displacement reaction Double displacement reactions A double displacement reaction generally occurs between compounds that are in aqueous solution. The general form is AX +BY → AY + BX A and B are positively charged ions and X and Y are negatively charged ions Types of DD reactions There are different types of DD reactions. We will learn three types: A reaction that forms a solid A reaction that forms a gas A reaction that forms water Determining the products of a DD reaction To do that you must first determine the ions that make up the reactants Ex LiCl (aq) + Pb (NO3)2 (aq) →  1. Reaction that form a solid and Solubility The solubility of a solute is the amount that can be dissolved in a given quantity of solvent at a given temperature. e.g. Pb(NO3)2 is 56 g/100 mL H2O at 20°C. It is temperature and pressure dependent Three categories: soluble, slightly soluble, and insoluble.  Solubility Rules and Double Displacement Reactions A double displacement reaction occurs if a precipitate forms, a gas is produced or a molecular compound like water is created. Solubility rules can used to determine if a reaction will occur in a double displacement reaction. If both the products are soluble (form ions in solution), then no reaction has occurred.  Double Displacement Reaction 3CoCl2(aq) + 2Na3PO4(aq) 🡪 Co3(PO4)2(s) + 6NaCl(aq) Will this reaction occur? A reaction will occur only if the following will be produced 1) Gas 2) Solid precipitate Solubility table Forming an Insoluble Product Pb(NO3)2(aq) + 2KI(aq) 🡪 PbI2(s) + 2KNO3(aq) Solubility Rules (common ionic compounds in water at 25 °C) Verifying Solubility Use your solubility chart to verify if the compound is soluble in water? a) MgCO3 b) AgNO3 c) MgCl2 d) Na3PO4 e) KOH Solubilities Not on the Table! Gases only slightly dissolve in water Strong acids and bases dissolve in water ◻ Hydrochloric, Hydrobromic, Hydroiodic, Nitric, Sulfuric, Perchloric Acids ◻ Group I hydroxides (should be on your chart anyway) Water slightly dissolves in water! (H+ and OH-) There are other tables and rules that cover more compounds than your table! Solubility Table  2. Double Displacement Reactions that Produce a Gas One product of the double displacement decomposes to give WATER and a GAS This type has two steps: 1. The double displacement 2. The decomposition of one of the products of double displacement to form water and a gas. Steps to solving double displacement reactions that produce a gas 1. Perform the double displacement: Na2CO3(aq) + HCl(aq) 🡪 NaCl(aq) + H2CO3(aq) (Very unstable so it decomposes). 2. Perform the decomposition: convert the unstable compound* into water and a gas. H2CO3(aq) 🡪 H2O (l) + CO2(g) (Recall from decomposition reactions: Acid 🡪 Non-metal oxide and water.) Trick: 1st subtract water from the formula of the acid: H2CO3 – H2O = CO2 (take out 2 H and one O) 3. Rewrite the original reaction and replace the acid in the original equation by water and the gas produced. Na2CO3(aq) + HCl(aq) 🡪 NaCl(aq) + H O (l) + CO (g) Double Displacement & Neutralization Neutralization Reaction: A special type of double displacement reaction that produces water and a salt. General Equation: Acid (Usually has H) + Base (usually has OH) 🡪 Water + Ionic Comp. (a salt: ionic compound produced by a neutralization reaction) Sample Problems: e.g. NaOH(aq) + HCl(aq) 🡪 NaCl(aq) + H2O(l) HNO3(aq) + NaOH(aq) 🡪 _______________________ KOH(aq) + H2SO4(aq) 🡪________________________ SrO(s) + HBr(aq) 🡪 ____________________________  Predicting the Products for a Chemical Reaction H2 O 2 🡪 ? 2) Is there only ONE reactant? If yes, then this reaction is a DECOMPOSITION REACTION So there should be two products, each being a separate element (i.e. Na, Ca, O2, I2, Br2) although that is not always the case 2H2O2 🡪 2H2O + O2  Predicting the Products for a Chemical Reaction Zn + SnCl2 🡪 ? 3) If there are 2 reactants, is one of them a pure metal on its own? If yes, then this reaction is a SINGLE DISPLACEMENT REACTION So the metal that is on its own must take the place of the other metal that is in the larger compound Zn + SnCl2 🡪 ZnCl2 + Sn  Predicting the Products for a Chemical Reaction NaCl + AgNO3 🡪 ? 4) Are both of the reactants compounds? If yes, then this reaction is a DOUBLE DISPLACEMENT REACTION So the two metals must switch places with one another, forming two new compounds NaCl + AgNO3 🡪 NaNO3 + AgCl  Predicting the Products for a Chemical Reaction C8H18 + O2 🡪 ? 5) Is one of the reactants oxygen gas? If yes, then this reaction is a COMBUSTION REACTION (as well as a SYNTHESIS REACTION) So the products must be an oxide and energy. If one of the reactants is a hydrocarbon, then CO2 + H2O are the products. 2C8H18 + 25O2 🡪 16CO2 + 18H2O + energy