Those electrons flow through the wire to the electrode in solution (Fig. At the negative terminal of the battery, electrons are produced. Demonstration materials and procedure are written in this activity.Įlectrolysis uses electricity to split water into hydrogen and oxygen. Observe a demonstration of a flame test to examine the gaseous products of electrolysis. The stopcocks can be opened or closed to allow the gases to be collected. Platinum electrodes conduct electricity and do not corrode. Platinum electrodes are at the bottom of the cylinders. The markings on the cylinders allow volumes of gases and liquids to be accurately measured. The U-tube consists of two upright cylinders joined by a horizontal tube. The middle tube has a funnel-like section at the top called a thistle tube that is used for filling the apparatus with the water that will be electrolyzed. Parts of a Hoffman Apparatus Labeled parts in Fig. Table 1.5 explains the parts of the Hoffman apparatus. It is a glass U-tube that is filled by a thistle tube (Fig. A circuit can consist of a battery and two wires connected to electrodes that go into a solution.Ī Hoffman apparatus is used for the electrolysis of water. For an electrical current to flow, a circuit has to be complete. In electrolysis, a chemical change is caused by electricity flowing through a chemical compound.Įxplore the composition of water using electrolysis. Electricity is the flow of electrons, the negatively charged particles in atoms. The process of electrolysis uses electricity to break bonds, causing decomposition of matter. Because water is an extraordinarily stable compound it does not decompose easily. Light decomposes hydrogen peroxide into water and oxygen (Fig. For example, calcium carbonate (lime stone) decomposes into calcium oxide (quick lime) and carbon dioxide when heated. Some compounds are decomposed by heating or by exposure to sunlight. The reaction for the decomposition of hydrogen peroxideĬompounds can be decomposed into simpler compounds or their elemental components by breaking bonds. Hydrogen peroxide yields water and oxygen gas The reaction for burning methane (main component of natural gas)Ī reactant breaks down into two or more products Methane plus oxygen yields carbon dioxide and water The subscripts i and j refer to the number of C and H atoms, which are different in different hydrocarbons. The reaction for the neutralization of stomach acid with an antacidĪ reactant made of carbon and hydrogen (a hydrocarbon) reacts with oxygen to form carbon dioxide and water. The reaction for polishing tarnished silver in a bath with aluminum foilĪ double switch is made between components of two reactantsĬalcium hydroxide plus hydrochloric acid yields calcium chloride plus water Silver sulfide plus aluminum yields silver and aluminum sulfide The simplified reaction for rust formationĪ single switch is made between components of two reactants Two or more reactants combine to form a product Types of common chemical reactions, with model reactions and example reactions Type of Reaction Examples of chemical reactions are given in Table 1.4. This reaction reads: calcium hydroxide plus hydrochloric acid yields calcium chloride plus water. The chemical reaction is written in this format: The water is formed from the OH in Ca(OH) 2 and the H in HCl, to make HOH, another way of writing H 2O. When these two reactants combine, they react to yield calcium chloride (CaCl 2) and water (H 2O). The chemical formula of an antacid is Ca(OH) 2. The above statement would be read “reactant plus reactant yields product and product.”Īn example of a chemical reaction is the neutralizing of stomach acid with an antacid. The arrow indicates that a chemical reaction has occurred. A chemical reaction is generally written in this format: The new substance that results from the chemical reaction is the product. The original substances are the reactants. In a chemical reaction, one or more substances undergoes a chemical change to produce a different substance or substances. There are many types of chemical reactions that result in chemical compounds, some of these are described in Table 1.4. Compounds are made of atoms of two or more elements joined chemically.
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