The displaced element (hydrogen) will be a product in its elemental form. Since zinc ions have a +2 charge, the formula for the zinc chloride product is ZnCl 2. In the above example, Zn atoms are displacing H atoms from HCl. ![]() The metals become ions with the charge shown on the table when they displace a cation.Įxample 1: Zn (s) + 2HCl (aq) → ZnCl 2(aq) + H 2(g) Additionally, a more active metal (higher in the table) can displace a less active metal (lower on the table) from a compound. The activity series will tell you which metals are sufficiently active to displace hydrogen from an acid. The higher a metal is on the activity series, the more active the metal. The activity series of metals can be used to predict whether a single replacement reaction involving metal atom (or hydrogen) replacement will occur.Īctive metals are effective at displacing cations from compounds. A metal will replace another metal (or hydrogen cation), and a nonmetal will replace another nonmetal. Both metals and nonmetals can be replaced in this manner. The displaced element B is a product in its elemental form. ![]() In the general form shown above, element A is replacing element B in the compound. Net ionic equation: 2H + (aq) + 2OH − (aq) → 2H 2O (l) Molecular equation: H 2SO 4(aq) + 2NaOH (aq) → Na 2SO 4(aq) + 2H 2O (l) An example of a neutralization reaction is the reaction of sulfuric acid with sodium hydroxide. In this type of reaction, the formation of a nonelectrolyte (water) drives the reaction to completion. In a neutralization reaction, an acid and a base reacts to form salt of the acid and water. Net ionic equation : Ca +2 (aq) + CO 3 -2 (aq) → CaCO 3(s)Īnother example of double displacement reaction is neutralization reaction. Spectator ions (Na + and Cl -) are omitted. The third and last type of equation, a net ionic equation is more concise and focuses only on ions that undergo a change. Ions that go through a reaction unchanged and that appear on both sides of the ionic equation are called spectator ions. The ionic equation for the above reaction is as follows. Refer to the rules predicting which salts are soluble in water when determining whether a compound is a weak or strong electrolyte, or a non-electrolyte. It is also necessary to know the formulas and charges of the ions that exist in solution. When writing ionic equations strong electrolytes should be expressed as ions while weak and non-electrolytes are expressed as molecules. Compounds that ionize completely or almost completely in aqueous solutions are called strong electrolytes while those that do not ionize or only ionize slightly are known as non-electrolytes and weak electrolytes respectively. In order to write an ionic equation, we need to be familiar with the way different compounds ionize in aqueous solutions. The second type of equation, the ionic equation, gives a more accurate description of the reaction that is taking place. Molecular equation: CaCl 2 (aq) + Na 2CO 3(aq) → CaCO 3(s) + 2NaCl (aq) We call this equation the molecular equation. The first type of equation we can write for this reaction shows the complete formulas of all reactants and products. After filtering off the solid, the remaining solution, on evaporation, would give a residue (NaCl). ![]() Analysis of the solid formed would reveal CaCO 3 as the precipitate. To demonstrate writing equations in all three forms, we will use the reaction between a solution of calcium chloride (CaCl 2) and a solution of sodium carbonate (Na 2CO 3). For example, stoichiometry problems are most easily solved using a molecular equation. There are situations where it is more convenient to use one of these equation types. There are three types of chemical equations commonly used to describe a double replacement reaction: molecular, ionic and net ionic equations. Reactions between two salt solutions and also acid-base neutralizations are double replacement reactions. \( \newcommand\)Ī double replacement reaction is one in which two compounds, AB and CD, “exchange partners" with each other to form two different compounds.
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