Chemical Reaction Model

Chemistry – Unit 7 Review Chemical Reaction Model 1. Describe key characteristics of all chemical reactions, including the role of energy. Explain how a balanced equation represents these features (include an example). All chemical reactions involve the rearrangement of atoms, requiring energy to break bonds and releasing energy when new bonds form, following the law of conservation of mass. A balanced chemical equation represents this by showing the same number of atoms of each element on both sides of the reaction, ensuring that mass is conserved. In chemical reactions, atoms recombine to form new substances in the product. A transfer occurs between the Chemical and thermal energy account. The balanced chemical equation represents the reaction symbolically, showing there are the same amount of atoms in the product as in the reactants In our 2 H? + O? ? 2 H?O + energy note: there are four atoms of H and 2 atoms of O on each side of the eq Applying the Model 2. Balance the reaction below by drawing any additional reactant and/or product molecules that would be needed. Write the balanced equation for this reaction. _________________________________________________________________________ Which of these molecules would be called reactants? ___________________________________________ 3. Balance these reactions. a. ___AgNO3(aq) + ____CaCl2(aq) ____AgCl(s) + ____Ca(NO3)2(aq) b. ____C2H6(g) + ____O2(g) ____CH3COOH(g) + ____H2O(g) c. ____HCl (aq) + ____Ba(OH)2(aq) ____BaCl2(aq) + ____H2O(l) d. ____Na(s) + ____H2O(l) ____NaOH(aq) + ____H2(g) e. When solid potassium chlorate is strongly heated in a flame it forms oxygen gas and solid potassium chloride. ll f. Zinc and lead (II) nitrate react to form zinc nitrate and lead. For the following chemical reactions, write the balanced chemical equation, including the energy term where it belongs. Also, complete the energy bar chart, the chemical potential energy graph and indicate if the reaction is exothermic or endothermic. 4. When 3M HCl is added to solid sodium carbonate, the contents of the test tube immediately starts bubbling and gets warm. Carbon dioxide gas, water vapor and sodium chloride are formed. 5. As solid ammonium nitrate dissolves in water, the resulting solution cools. 6. What type of reactions are the following? a. MnI2(s) Mn(s) + I2(s) ___Decomposition_______________________ b. C2H5OH(l) + 3 O2(g) 2 CO2(g) + 3 H2O(g) Singular Replacement____________________ c. CaCl2(aq) + Na2CO3(aq) CaCO3(s) + 2 NaCl(aq) _Double Replacement_________________________ d. CO(g) + Cl2(g) COCl2(g) ____Synthesis______________________ e. Zn(s) + CuSO4(aq) Cu(s) + ZnSO4(aq) ____Singular Replacement______________________ 7. What evidence do we have that a chemical reaction has occurred? Name 2-3 examples. Change in temperature, change in color, formation of gas, formation of a precipitate (such as a formation of a solid), 8. What observations can be made that would indicate that a reaction is either endo or exothermic? temperature changes: a decrease in temperature suggests an endothermic reaction, while an increase suggests an exothermic one. 9. Review the nail lab and the post lab questions in the lab.