Chapter 6 and 16:

FR17 - e.Using the standard entropy values given in the table above, calculate the standard entropy for the decomposition of sodium bicarbonate.

2(136) + 214+70 - (2(102)) 420 - 204 216 t/MOL =^S

FR17- c.Determine the students experimental value of ^H* for Reaction 1 and 2 in units of KJ/ mol

1) 5.61/54.01 = 0.0668 mol 3.68Kj/ 0.0668 mol = 55.1 KJ/mol • 2)(.47/105.99 = .0893 mol -3.223/ .0893 mol= -36.1 Kj/mol

FR17- b.Calculate the magnitude of the q, the thermal energy of change for reaction 1 and reaction.

1) q= (225.0+5.61)(4.2)(-3.80)= -3680J • 2) q= (224.5+9.47)(4.2)(-3.28)= 3223J

1 Which of the following arranges the above molecules C2H6, C2H4, and C2H2) in order of their carbon to carbon enthalpies from least to greatest.

D. C2H6 < C2H4 < C2H2

The potential energy as a function of internuclear distance for the three carbon to carbon bonds in ethane, ethene and ethyne, is shown in the graph above. Based on the data in the graph, which of the following correctly identifies the carbon to carbon bonds as X, Y, and Z.

X Y Z B. C2H2 C2H4 C2H6

FR17- F.Calculate the standard free energy of the decomposition of sodium bicarbonate

^G-^H-T^S ^G= 146.3 KJ/ mol - (298k)(.216 KJ/mol) ^G= 81.9 KJ/ mol

6 Based on the bond energies shown in the table above, which of the following diagrams best represented the changes in energy as the reaction represented below proceeds?

a THE ANSWER IS GRAPH A

8 A 10 g cube of copper at a temp (t1) is places in an insulated cup containing 10g of water at a temp (T2). If T1>T2 which of the following is true of the system when it has attained thermal equilibrium?

a.The Temp of the copper changed more than the temp of the water

10 The potential energy of the system of two atoms as a function of the internuclear distance is shown in the diagram above. Which of the following is true regarding the forces between the atoms when their internuclear distance is X?

a.The attractive and repulsive forces are balanced, so the atoms will maintain an average internuclear distance x.

11 The synthesis of H20 from O2 and H2 is represented by the equation above. Which of the following statements is true about the bond energies in this reaction?

a.The energy absorbed as the bonds in the reactants are broken is greater than the energy released as the bonds in the product are formed.

5 Which of the followuing is true for the combustion of C3H8 according to the data above

b. ^S > 0 and ^G < 0

14 Which of the following best describes the flow of heat when 1.0 mol XY2 decomposes?

b.50 kJ of heat is transferred from the surroundings

9 The decompisituion of H2O2, represented by the equation below is thermodynamically favorable. The signs ^G* and ^S* for the reaction are which of the following?

b.Negative Positive

A hot iron ball is dropped into a 200g sample of water initially at 50 C. if 8.4 Kj of heat is transferred from ball to the water, what is the final temp of the water?

c. 60. *C

4 Calculate the standard heat of combustion for propane (C3H8)

d. -1900

7 Which of the following equations represents a reaction for which the standard entropy change is positive (^S* > 0)

c.CaCO3(s) -> CaO(s) + CO2(g)

13 The heating curve for a sample of pure ethanol is provided above. The temp was recorded as a 50.0g smaple of solid ethanol was heated at a constant rate. Which of the following explains why the slope of segment T is greater than the slope of segment R?

c.The heat of vaporization of ethanol is less than the heat of fusion of ethanol

12 Based on the info above, what is the enthalpy change for the sublimation of iodine, represented below?

d.62KJ / mol(rxn)

FR17. A student was assigned the task of determining the enthalpy change for the decomposition of solid sodium bicarbonate as represented by the reaction above. To do this, the student used a polystyrene cup calorimeter and preforms two reactions: the raction between solid sodium bicarbonate and excess aqueous hydrochloric acid (reaction 1) and the reaction between solid sodium carbonate and excess aqueous hydrochloric acid (reaction 2). Data for each reaction is shown in the table. a.According to the data, datermine if reaction 1 will be endothermic or exothermic and explain why

• Change in temp is -3.80, which means that the reaction is endothermic. As it is absorbing heat from the surroundings.

FR17- g. is the decomposition reaction of sodium bicarbonate spontaneous?

• No, because the standard free energy is positive so it would not be able to happen spontaneously ( it would need energy to be completed )