Chemistry Unit 6 Study Guide You may use this study guide to review for your test; practice your new skills or review old concepts. Each topic has several questions relating to it, this should help with giving you plenty of practice.

Exothermic and Endothermic AA B CBC ∆H AA B CBC Characteristics of a Reaction A BA B CC Factors Affecting Equilibrium ABC K eq of reactions- conceptual AA B CBC Activation Energy AA B CBC Equilibrium AA B CBC K eq of reactions- mathematical AA B CBC

Exothermic and Endothermic A In an exothermic reaction is energy one of the products or one of the reactants? It is a reactant

Exothermic and Endothermic B In an endothermic reaction is energy one of the products or one of the reactants? It is one of the reactants

Exothermic and Endothermic C IN the following reaction is it endothermic or exothermic? CH 4 + 2O 2 → CO 2 + 2H 2 O kJ exothermic

∆H A If the H of a reaction is positive is the reaction endothermic or exothermic? endothermic

∆H B ∆H B If E2 < E1 this reaction is endothermic or exothermic? exothermic

∆H C If the H is negative is the reaction endothermic or exothermic, why? Exothermic, because the products have more energy than the reactants

Characteristics of a Reaction A What are the ways that we can identify if a reaction has occurred? Color change, formation of a precipitate, change in temperature, gas given off

Characteristics of a Reaction B When heat is produced as a product, explain on a molecular level what is occurring. The energy required to break the reactants apart is more than the energy given off when the new bonds of the product form and therefore the extra energy is given off as heat.

Characteristics of a Reaction C Why would the formation of a precipitate be a good indicator of a chemical reaction? Because the new compound that is being made is insoluble in the solution and therefore settles out as a solid. The original compounds were soluble so since we saw a change in the solubility there must have been a change in the formula.

Factors Affecting Equilibrium A What are the factors that might affect equilibrium? Change in temperature, change in concentration of reactants or products, pressure of the system

Factors Affecting Equilibrium B If you have an exothermic reaction and you increase the temperature of the system what will happen to the equilibrium and why? The equilibrium will shift to the reactants because the endothermic side of the reaction will be favored.

Factors Affecting Equilibrium C If you increase the pressure in a system how will that affect the equilibrium? The side of the reaction with the fewest number of molecules will be favored.

K eq of Reactions- conceptual A Write the K eq of the following reaction. CuSO 4 + 2HNO 3 → Cu(NO 3 ) 2 + H 2 SO 4 K eq = [Cu(NO 3 ) 2 ] [H 2 SO 4 ] [CuSO 4 ] [HNO 3 ] 2

K eq of Reactions- conceptual B What is the K eq of the following reaction? 3Ca(OH) 2 +2 AlBr 3 → 3CaBr 2 + 2Al(OH) 3 K eq = [CaBr 2 ] 3 [Al(OH) 3 ] 2 [Ca(OH) 2 ] 3 [AlBr 3 ] 2

K eq of Reactions- conceptual C In the following reaction what do the lowercase letters represent? aA + bB → cC + D The coefficients used to balance the reaction.

Activation Energy A What is activation energy? The energy required to start a chemical reaction.

Activation Energy B How can we decrease the activation energy of a reaction? A catalyst will decrease the amount of activation energy required for a chemical reaction without changing the reaction itself.

Activation Energy C Do exothermic reactions have an activation energy? Do spontaneous reactions have a higher or lower activation energy? Exothermic reactions have some form of activation energy but spontaneous reactions have such low activation energies that the energy of the environment is enough to start the reaction.

Equilibrium A What is equilibrium? A situation in which a chemical reaction occurs equally in a forward and backward direction. So we are forming products at the same rate that the products are breaking and forming reactants.

Equilibrium B Do all reactions reach equilibrium? If left long enough all reactions will reach equilibrium.

Equilibrium C What happens if we change an environmental factor such as increasing the temperature or pressure? The equilibrium of the reaction will shift until the new balance is aquired in the new environment.

K eq of Reactions-Mathematical A For the following reaction what is the K eq ? 2H 2 + O 2 → 2H 2 O H 2 = 1.5 M; O 2 = 3 M; H 2 O = 2M K eq = (2 M ) 2 (1.5 M) 2 (3M) = 0.59

K eq of Reactions-Mathematical B Find the K eq for the following reaction. CH O 2 → CO 2 + 2H 2 O CH 4 = 2.1 M; O 2 = 1.1 M; CO 2 = 3.3 M; H 2 O = 1.2 M K eq = (3.3 M)(1.2 M) 2 (2.1M)(1.1 M) 2 = 1.87

K eq of Reactions-Mathematical C Find the K eq for the following reaction. NaCl + HOH → HCl + NaOH NaCl= 9.5 M; HOH = 10.0M ; HCl = 4.00M; NaOH = 4.00M K eq = (4.00M)(4.00M) (9.60M)(10.0) = 0.167