Thermochemistry reveiw assignment answers PDF

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Thermochemi misstry Review True/False 1. A reaction with a negative enthalpy value converts potential energy into kinetic energy. 2. The equation 2H2(g) + ½ O2(g) → 2 H2O(g) + 483.6 kJ is an exothermic reaction. 3. For the reaction:

if the rate of production of H2 is 0.4 mols/sec,

then the rate with respect to HCl r = -0.8 mols HCl/sec 4. The value of the rate constant, k, is valid only for a specific reaction at a specific temperature. 5. If a salt is dissolved in water and the temperature of the water is reduced, the reaction is exothermic. Multiple Choice 6. The diagram to the right shows a. an exothermic reaction b. a reaction with 3 intermediate steps c. a reaction that converts potential energy into kinetic energy d. both a and b are correct e. all of the above 7. If the concentration of a reactant is doubled and the rate increases by a factor of 8, the order of reaction with respect to the reactant is: a. 1 b. 2 c. 3 d. 4 e. 6 8. If ∑∆Hf of a reactants is -437 kJ and the ∑∆Hf of a products is 543 kJ, the ∆H of the reaction is: a. -209 kJ d. +106 kJ b. +980 kJ e. Not enough information to determine c. -106 kJ 9. Which statement best describes 1st order reactants: a. They are the first reactants written in the balanced equations b. They have no effect on the rate of the chemical reaction c. If the concentration of the reactant is doubled, the rate of the reaction will also double. d. Increasing the concentration of a first order reactant will slow down the rate of the reaction e. None of the above statements accurately describe 1st order reactants 10. Which of the following is not a factor that controls the rate of the reaction a. chemical nature of the reactants d. catalyst b. concentration of the reactants e. temperature c. the number of products formed

Shor ortt Answers 1) Calculate ∆H for the following reaction using the thermochemical equations listed below

HCl(g) + NaNO2(s) ----> HNO2(l) + NaCl (s) 1) 2) 3) 4)

2 NaCl(s) + H2O(l) → 2 HCl(g) + Na2 O(s) NO(g) + NO2(g) + Na2O(s) → 2 NaNO 2(s) NO(g) + NO2(g) → N2O(g) + O2(g) 2 HNO2 (l) → N2O(g) + O2(g) + H2 O(l)

∆H1 = +507.3 KJ ∆H2 = -427.1 kJ ∆H3 = -42.6 kJ ∆H4 = +34.3 kJ

2) The initial rate of the reaction has been measured at the reactant concentrations shown Initial rate (mol/(L·s)) Trial [ClO3-] [Cl-] [H+] 1 0.10 0.10 0.10 4.0  10 -5 2 0.20 0.10 0.10 3.2  10 -4 3 0.10 0.20 0.10 4.0  10 -5 4 0.10 0.10 0.20 8.0  10 -5 i) Determine the rate law for this reaction at the experimental temperature.

ii) Calculate the initial rate of the reaction concentrations of all 3 reactants = 0.50 mol/L?

3. Given the following reaction CH 4 + 2O2 → CO2 + 2H2O, determine the avg. rate of H2O(g) production in g/sec if the mass of CH 4 is 16.5 g @ 2 min. and 3.6 g @ 4 min.

4a) Use the Hof on the thermodynamics chart to determine the molar enthalpy change that occurs during the incomplete combustion of glucose,

C6H12O6 (s) + 7O2(g) → 2CO2(g) + 6H2O(g) + 4CO(g)

4b) Determine the enthalpy change that occurs when 500 g of glucose is incompletely combusted.

5) Calculate the molar enthalpy of combustion for C8H18 based on the data below… Volume of Water Mass of Al calorimeter Initial Temp Final Temp I nitial mass of the fuel Final mass of the fuel

750 ml 760 g

12 oC 82oC 25.2 g 19.6 g...