A chemical reaction is the process where new substance(s) with new properties are produced by reacting two or more substances. Based on qualitative observations, conclusions can be drawn if a chemical reaction has occurred. This can be indicated by a change in colour, change in temperature, formation of a precipitate, light emission, or gas.
Two types of chemical reactions investigated this lab are single displacement and double displacement reactions.
A single displacement reaction is a chemical reaction where one element replaces another element in a compound. It can be represented by A + BC à AC + B where A is a metal or D + BC à BD + C where D is a non-metal. The reactants in a single displacement reaction always include a pure element such as oxygen gas or zinc metal along with an aqueous compound. Once the single displacement reaction occurs, the new product is a new aqueous compound and a different pure element. However, not all metals can replace metals, and not all non-metals can replace non-metals. To predict the faith of the reaction, it is important to look at the activity series. The activity series ranks the elements based on their reactivity. Only the more reactive elements on the activity series are able to replace the less reactive elements.
A double displacement reaction is a chemical reaction where the cations (or anions) of two different compounds switch places, resulting in two new compounds. This can be represented by AB + CD à AD + CB. Double displacement reaction can be classified as precipitation reactions, neutralization reactions, or gas forming reactions. Double displacement reaction will result in precipitation if one or more of the products produced is an insoluble ionic compound based on the solubility chart. As well, when an acid and a base react, a displacement reaction results in a neutralization reaction where the products are water and salt (ionic compound). In some double replacement reactions, a gas can be produced as one of the products. An example is the reaction between NaCO3 and HCl producing carbon dioxide gas.