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CHE 106 Lecture Notes - Lecture 4: Calcium Chloride, Chemical Formula, Chemical Equation

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CHE 106 Full Course Notes

CHE 106 Full Course Notes

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Stoichiometry- the calculation of the quantities of reactants and products involved in a chemical reaction. It is based on balanced chemical equations and on the relationship between mass and moles. Chemical equations are concise representations of chemical reactions. Coefficients are inserted to balance the equation to follow the law of conservation of mass. Na + cl2 nacl not balanced because 2 chlorines on left, only 1 on right. To balance, na+cl2 2 nacl 2na(s)+cl2 2nacl. Two or more substances react to form one product. When one substance breaks down into two or more substances. Generally rapid reactions that produce a flame, most often involve oxygen in the air as a reactant. Ch3oh + o2 co2 + h2o balanced= ch3oh + (3/2)o2 ch2+2h2o. 2ch3oh + 3o2 2co2 + 4h2o. The sum of the atomic weight for the atoms in a chemical formula. The formula weight of cacl2 (calcium chloride) is: (weight of calcium) + 2(weight of chloride)

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Science Tutor: Chemistry Name: Mixtures, Solutions, &Compounds: Chemical Equations Date Chemical Equations If a chemical symbol can be thought of as a letter and a chemical formula as a word in the language of chemistry, then a chemical equation is a statement or sentence. A chemical equation is a shorthand way of describing a chemical reaction between two or more substances. A "+ sign means "combines with." An arrow points away from the reactants and toward the products (See page 10), and an arrow means "yields." 2Na + Cl2 â 2NaCl means sodium combines with chlorine to yield sodiumn chloride (salt) Look closely at the equation above. Notice the "2" in front of NaCI on the right and Na on the left. That 2, called a coefficient, is necessary to make this equation balance. Remember Antoine Lavoisier? (Page 15) Matter is neither created nor destroyed in a chemical reaction. The same number of each kind of atom must be on both sides of a chemical equation. Because chlorine only exists as a molecule consisting of two chlorine atoms, it requires two atoms of sodium to yield two molecules of salt (NaCI). This illustrates another important law stated clearly by the French chemist Joseph-Louis Proust in 1799. Chemical compounds always combine in certain specific fixed proportions. Wherever sodium and chlorine combine, two atoms of sodium will be necessary to react with one molecule of gaseous chlorine. 1 . For the equation 2Mg + O2â 2MgO + energy: A. List the reactant or reactants 2Hato B. List the product or products C. How many atoms of magnesium does it take to combine with one molecule of oxygen? D. How many molecules of magnesium oxide are produced in this reaction? 2. Hydrogen can combine with oxygen to produce water. We could write the equation like this: H2 + O2 â H2O. But this equation is unbalanced! Rewrite this equation with the correct coefficients so that an atom of oxygen doesn't disappear! (Be careful. If you add a coefficient to one side you may have to adjust the other. Count all the atoms.) 3. Now that you have the idea, balance the following equations: A, Pho, â PbO + 02 C. Ca + H2O â Ca(OH)2 + H2 How is following a recipe to mix up a batch of biscuits (or any other food item) similar to Proust's law for chemical reactions? 4. OMark Twain Media, Inc., Publishers 17

Zinc and Copper(II) Sulfate Materials: Two test tube rack, 1 M CuSO_4 (copper(II) sulfate notation). Zn(s) For all the experiments in pans C-F, use small quantities. For solids, use the amount of compound that will fit on the tip of a spatula or small scoop. Carefully pour small amounts of liquids into your own beakers and other container. Measure out 3 ml, of water in a test tube. Use this volume as a reference level for each of the experiments. Do not place droppers or stirring rub into reagent bottles. They may contaminate a reagent for the entire class. Discard unused chemicals as indicated by your instructor. B.l Pour 3 ml. (match the reference volume) of the blue solution. 1 M CuSO_4 (one molar copper(II) sulfate), into each of two test tubes. Obtain a small piece of zinc metal. Describe the appearance of the CuSO_4 solution and the small piece of zinc metal. Add the Zn metal piece to the CuSO_4 solution in one of the test tubes. The CuSO_4 solution in the other test tube it your reference for the initial solution color. Place the test tubes in your test tube rack and observe the color of the CuSO_4 solutions and the Zn piece again at 15 and 30 minutes. Pour the CuSO_4 solutions into the sink followed by a large amount of water. Rinse the piece of zinc with water and place it in a recycling container as directed by your instructor. B.2 Balance the equation given for the reaction. The symbol (aq) means aqueous (dissolved in water). Unbalanced equation: Zn(s) + CuSO_4(aq) rightarrow Cu(s) + ZnSO_4(aq) B 3 Identify the type of reaction that that occurred. Metals and HCl Materials: Three test tubes, test tube rack, small pieces of Cu(s), Zn(s), and Mg(s) metal 1 M HCl Caution: HCl it a carrot ire acid. Handle carefully! C.l Place 3 mL of I M HCl (match your reference volume from part Cu(s) in each of three test tubes. Describe the appearance of each metal. Carefully add a metal piece to the acid in each of the test tubes. Record any evidence of reaction such at bubbles of gas (H_2). Carefully pour off the acid and follow with large quantities of water to dilute. Rinse the metal pieces with water, dry, and return to your instructor C.2 Balance the equation given for each metal that gave a chemical reaction. If there was no reaction, cross out the products and write NR for no reaction. Unbalanced equations: 1.Cu(s) + HCl(aq) rightarrow CuCl_2(aq) + H_2(g) 2. Zn(s) + HCl(aq) rightarrow ZnCl_2(aq) + H_2(g) 3. Mg(s) + HCl(aq) rightarrow MgCl_2(aq) + H_2(g) C.3 Identify the type of reaction for each chemical reaction that occurred. Reactions of Ionic Compounds Materials: Three (3) test tubes, test tube rack Dropper bottle sets of 0.1 M solutions: CaCl_2, Na_3PO_4, BaCl_2, Na_2SO_4, FeCl_3, KSCN For each of these reactions, two substances will be mixed together. Describe your observations of the reactants before you mix them and then describe the products of the reaction. Look for changes in color, the formation of a solid (solution turns cloudy), the dissolving of a solid, and/or the formation of a gas (bubbling). Balance the equations for the reactions. Dispose of the solutions properly. D.1 Place 20 drops each of 0.1 M CaCl_2 (calcium chloride) and 0.1 M Na_3PO_4 (sodium phosphate) into a test tube. Describe any changes that occur. Identify the type of reaction for each chemical reaction that occurred. Unbalanced equation: CaCl_2(aq) + Na_3PO_4(aq) rightarrow Ca_3(PO_4)_2(s) + NaCl(aq).

If you could answer the rest of Question 1 from the 6th and 7th picture and then Question 3 from the 8th and 9th picture

11 Oxidation-Reduction Reactions Introduction We encounter oxi uction reactions every day Examples include the combustion of coal natural gas, oil, and gasoline, the operation of automobile's battery and the sains by a Although there are a variety of oxidation-reduction reactions .when you compare a number of you can some common featu Each these of simultaneous oxidation and reduction because electrons are lost by one atom and gained by another one. Moreover, the reactants include an agent and a reducing agent always lost agent and gained by the oxidizing agent (Ebbing/Gammon, Section 4.5) Purpose You will begin by preparing aqueous solutions of three halogens: Cl2, Bra, and Iz. You will prepare these substances in solution from stoichiometric quantities of certain oxidizing and agents. By observing the effect ofthese halogens on the corresponding halides (CI,Br, and you will be able the halogens according to their oxidizing strengths and the halides according to their reducing strengths. Your subsequent observations on the reactions of two halides, Br and I with two common oxidizing agents will enable you to rank the latter according to their oxidizing strengths. You will also find that the products obtained from an oxidation-reduction reaction in an acidic solution can differ markedly from those obtained in a basic solution. Finally, and most important, you will write a balanced equation for each reaction that you have observed The Halogens and the Halides You will deal with halogens and halides in each part ofthis experiment. A brief description of some of their properties will enable you to understand some of your observations more easily. The halogens are found in Group VIIA of the periodic table. The members of this group are fluorine (F) chlorine (CI, bromine (B), iodine (i) and astatine these elements belong to the same 12, group, have many similar properties. For example, their elemental diatomic (F2.cl. Br2, they Atal, and each of them is an oxidizing agent. This experiment uses only Cl, Bra, and Iz, however, because F is such a strong oxidizing agent that special conditions are required for its study and because astatine is radioactive. Aqueous solutions ofcl, be prepared either by dissolving these elements in water or by generating them in Br, reactions. Aqueous solutions of these halogens are solution as products of certain oxidation-reduction respectively. Each called chlorine water, brominee and iodine thickness solution. has its own characteristic color, depending on the concentration and red-brown to water is colorless to yellow; bromine water is yellow to red-brown; and iodine water is brown These halogens are also soluble in cyclohexane (C6H12, a substance that is itselfinsoluble in water. layer When cyclohexane is added to an aqueous solution of a halogen, two layers are formed. The upper is cyclohexane, because it is insoluble and less dense than water. A portion of the halogen passes from the aqueous layer to the upper cyclohexane layer (a process called extraction). A characteristic color is then imparted to this layer. The color ofa halogen in cyclohexane differs somewhat from its color in an aqueous solution, as you will discover during the experiment. be scanned, copied or duplicated or possed toa publicly accessible webwie, iawhole or in Cengage Leaming All Rights Resened c 2013