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Experiment No. 4 Stoichiometry and The Laws of Chemical Reactions The law of conservation of mass, the law of definite proportions, and the law of multiple proportions summarize the laws describing chemical change. The law of conservation of mass states that during a chemical reaction, mass is neither created nor destroyed. This means that total weights of substances before they react should be the same as the weights of the products after the reaction. Analysis of compound shows that when elements combine to form a given compound, they always combine in the same ratio by weight. This is known as the law of definite proportions. This does not mean that when any amount of two substances are mixed, all of these would react with each other. A part of either one of the substances could be left unreacted. This means that there is a limit to the amount of the substance that can be chemically combined with a fixed weight of another. The law of multiple proportions states that when elements combine to form more than one compound, the weight of one element combined with a fixed weight of the other elements is in ratios of small whole numbers. Experiment No. 5 Chemical Periodicity I. Introduction The arrangement of elements in the order of increasing atomic number with the elements having similar properties placed in the vertical column is known as the periodic table. The elements that belong to the same group often exhibit similarities in their physical and chemical properties because they have the same type of arrangements of electrons at the periphery of their atoms. Elements found in the same horizontal row have the same number of energy levels that cannot be expected to behave in similar ways. Experiment No. 6 Types of Chemical Reactions and Factors Affecting the Rates of Chemical Reactions I. Introduction Chemical reactions can be classified into four types: 1) direct union or combination, 2) decomposition, 3) single displacement, and 4) double displacement. Direct combination or synthesis involves the union of two or more elements or compounds to produce only one product which is a more complex substance. Decomposition reactions occurs when a single compound decompose, usually upon heating, into two or more elements or compounds as products. In single displacement reactions, a free element replaces an element in a compound forming a new compound and the resulting release of the element displaced. In this type of reaction, a more active element will displace a less active one. In double displacement reactions, both compounds react by exchanging their metallic and nonmetallic part thus forming two new compounds. The rate of a chemical reaction is influenced by many factors, namely the nature or type of reactants involved, the concentration of the reactants, the temperature, the surface area of the solid reactants, and the presence of a catalyst. Experiment No. 7 Chemical Equilibrium I. Introduction Any system at equilibrium represents a dynamic state in which two or more opposing processes are taking place at the same time and at the same rate. A chemical equilibrium is a dynamic system in which two or more opposing chemical reactions are going on at the same time and at the same rate. The concentration of products and reactants seem unchanged and the system appears to be in standstill because products are reacting at the same rate they are formed.