Week 5 Notes (2/16 and 2/18)
Week 5 Notes (2/16 and 2/18) Chem 107
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This 3 page Class Notes was uploaded by Kelly Johnson on Thursday February 18, 2016. The Class Notes belongs to Chem 107 at West Chester University of Pennsylvania taught by Jacqueline Butler in Winter 2016. Since its upload, it has received 54 views. For similar materials see General Chemistry for Health Science in Chemistry at West Chester University of Pennsylvania.
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Date Created: 02/18/16
Chemistry Unit 2- Chapter 4 Notes 1. Chemical Equations and Calculations a. Moles and Molar Mass i. Avogadro’s Number 1. Represents the number of atoms in 1 mole of any substance 2. 1 mole = 6.02 x 10 23 ii. Molar Mass 1. This is equal to one mole of any substance 2. This is also equal to the atomic mass ( LISTED ON THE PERIODIC TABLE) in grams of an element 3. 1 mole= molar mass(g)= 6.02x10 particles/atoms 4. To calculate the mass, add grams to the end of the atomic mass. This represents how many grams make up a mole. iii. Molar mass of a compound 1. To calculate the molar mass of a compound, add the mass of the present elements together. If there are multiple of one element, take this into consideration. **** EXAMPLES PRESENT ON HER D2L PAGE AS WELL AS DONE IN CLASS. CONTACT ME PERSONALLY IF YOU WISH TO GO OVER THESE PROBLEMS IN PERSON. b. Chemical Reactions i. Evidence 1. Releasing of a gas a. Normally appears as bubbling b. Ex. CO 2s released when acid is placed in a solution containing carbonate ions 2. Formation of a solid (precipitate) a. A solid may form when two aqueous solutions are combined + b. Ex. A solution containing Ag ions mixed with a solution of Cl ions form AgCl which is a solid 3. Heat is produced or absorbed a. May feel hot or cold b. Ex. When an acid and base are mixed together 4. Color Changes ii. Writing Chemical Equations 1. Patterns a. Many may follow patterns, and recognizing these patterns will make understanding reactions easier 2. Types a. Combination i. The joining of two or more separate elements/compounds into products of a different composition ii. A + B =AB iii. Ex. 2Na (s) + C2 (g)= 2NaCl(s) b. Decomposition i. A single reactant breaks down to form two or more products ii. Reverse of a combination iii. AB = A + B iv. Ex. 2HgO (s) = 2Hg (l) + O2(g) c. Replacement i. Single replacement 1. One atom replaces another to produce a new compound 2. Swapping partners 3. A+BC=B+AC ii. Double replacement 1. Two compounds switch partners 2. Exchange of atoms to produce a new compound 3. AB+CD=AC+BD d. Precipitation i. Reaction of two aqueous solutions of ionic compounds that produce an ionic compound that is insoluble in water ii. Insoluble product is called the precipitate iii. Simply, something will dissociate from water and reform something else iv. Key to identifying- if you see a solid formed, it is a precipitate reaction iii. Solubility Rules 1. Will not have to know specifics 2. Of ionic compounds a. Some dissolve very well in room temperature water = SOLUBLE b. Others hardly dissolve at all I room temperature water = INSOLUBLE 3. There is a chart if you are interested iv. Ionic equations 1. Equations that describe the chemicals put into water and their products are known as molecular equations 2. Equations that describe the actual dissolved species are known as complete ionic equations a. You need to be able to predict if these will dissociate v. Reaction types 1. Gas Evolving a. A gas will form directly from the ion exchange or by the decomposition of one of the reactants into a gas and water b. These reactants may be unstable which allows them to break down easily 2. Acid-Base a. Will be covered later b. Transfer of a hydrogen ion from an acid to a base, this is known as neutralization as both will lose their charges 3. Oxidation-Reduction a. Will also be covered later b. Transfer of one or more electrons from one reactant to another c. Ex. Occurs in batteries 4. Combustion a. Hydrocarbon and oxygen (O ) com2ine to form carbon dioxide and water vi. Chemical Reaction Equations 1. Definition of a Chemical Reaction equation a. A symbolic representation of a chemical reaction in terms of chemical formulas b. Includes reactants on the left, products on the right, and an arrow which symbolizes yields c. States of matter should be identified in the equation 2. Law of conservation of mass a. The total number of atoms of each element must match on both sides of an equation b. This is known as being balanced 3. Examples of balancing equations were done in class and worksheets are on D2L a. Final answers for class problems i. O + 2PCl 2POCl 2 3 3 ii. P4+ 6N O2 P O4+ 6N 2 iii. 2F2+ 2H O2 4HF + O 2 iv. 2H 3O +43Ca(OH) Ca2PO ) + 6H 4 2 2
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