Energetics Questions and Answers

meters molar heat capacity heat Label each variable in the given calorimetry equations with the property it represents charge mass change in time specific heat capacity change in temperature Avogadro s number number of moles q cxmx AT q Cxnx AT m

Green plants use light from the Sun to drive photosynthesis Photosynthesis is a chemical reaction in which water H O and carbon dioxide CO chemically react to form the simple sugar glucose C6H 2O6 and oxygen gas O What mass of water is consumed by the reaction of 8 99 g of carbon dioxide Round your answer to 3 significant digits

For the reversible one step reaction A A B C and the rate constant for the reverse reaction k is the rate constant for the forward reaction k is 281 L mol min 387 L mol min at a given temperature The activation energy for the forward reaction is 41 2 kJ mol whereas the activation energy for the reverse reaction is 23 4 kJ mol Determine the equilibrium constant K of this reaction K Determine whether this reaction is endothermic or exothermic endothermic O exothermic What effect will raising the temperature of the reaction have on the rate constants and the equilibrium constant Raising the temperature will increase the forward rate constant k more than it will increase the reverse rate constant k 1 resulting in an increase in the equilibrium constant K O Raising the temperature will increase the reverse rate constant k1 more than it will increase the forward rate constant k resulting in a decrease in the equilibrium constant K Raising the temperature will not affect either rate constant or the equilibrium constant K Raising the temperature will increase the forward rate constant k and reverse rate constant k1 equally leaving the equilibrium constant K unchanged

2 Cyclopropane isomerizes exothermically to propene as shown H 4 0 H C C H 1 I A 308 kJ mol C 423 kJ mol CIH H HIC C H H H AH 32 kJ mol 1 1 H H cyclopropane propene The C C single bond in propene has an estimated bond dissociation enthalpy BDE of 345 kJ mol while the C C double bond in propene has a BDE of 611 kJ mol Assuming that the C H bonds in propene and cyclopropane all have the same BDE what is the estimated BDE of a C C single bond in cyclopropane B 329 kJ mol 1 D 924 kJ mol

21 Which of the following equations correctly describe the change in internal energy AE of a reaction taking place in a bomb calorimeter I II AE q AE AH VAP A I only C Both I and II B II only D Neither I nor II

26 Calculate AG using the Gibbs Free Energy equation at standard temperature State whether or not the reactic will be spontaneous AH 638 4 kJ AS 156 9 J H CH3OH 1 5 02 CO2 2 H O

7 The frequency of blue light is 6 67 x1014 Hz How much energy does a photon of blue light carry h 6 626 x 10 34 J s 1 eV 1 60 x 10 19 1 56 eV 4 42 eV 2 76 eV

24 How much heat is transferred when 75 g of iron C 0 45 J g C is heated from 30 C to 650 C

The next three problems are linked together You will need this conversion 1 cal 4 18 J P 750 kg of iron are cooled from 100 C down to 25 C cp 4 6 x 10 J g C What amount of heat in calories and Joules was lost by the iron Answer q 6 2 X 106 cal 2 6 X 107 J The iron in the previous problem was cooled by submerging it in water at 10 C How much heat in calories and Joules was absorbed by the water Answer q 6 2 X 106 cal 2 6 X 107 J If the specific heat of water is 4 18 J g C how much water in kilograms at 10 C was required to cool down the iron wor 112 Izg

Order the substances A B C D and E by their specific heat capacities from highest 5 to lowest 1 Assume the masses of each sample are the same Change in Temperature vs Heat Added Temp C A C B Heat Energy Added 1 D

Use the information and table to answer the following question A student wanted to determine the enthalpy change of the reaction The standard enthalpies of formation are shown along with her calculations CO C 0 Substance CO C s Diamond 0 AH 393 5 kJ mol 1 88 kJ mol 0 kJ mol AHreaction 393 5 kJ mol 1 88 kJ mol AHreaction 395 38 kJ mol Did the student perform the calculation correctly OA No because the student subtracted AH of products minus AH of reactants OB No because the student subtracted AH of reactants minus AH of products OC Yes because the student subtracted AHF of reactants minus AH of products O D Yes because the student subtracted AH of products minus AH of reactants

What is the energy input needed to heat 100 g frozen ethanol from 150 C to 110 C try looking up ethyl alcohol if you can t find the information for ethanol

Isopropanol C3H8O has a heat of of energy will be absorbed by 271 mL of isopropanol in order to evaporate at that temperature d 0 790 g mL vaporization of 45 4 kJ mol at 25 0 C How many joules 464 00

4 When the sun is high in the sky it delivers approximately 1000 watts of power to each square meter of the earth s surface The temperature of the surface of the sun is about 6000 K while that of the earth is about 300 K Estimate the entropy created in one year by the flow of solar heat onto a square meter of the earth Assume an average of 8 hours of sunlight per day

Calculate the amount of heat energy that must be added to change 23 5 g ice at 15 C to liquid water at 45 C

1 Write the thermochemical equation for the formation of calcium sulphate under standar conditions ii Calculate enthalpy of reaction for the given chemical equation CaSO4 s Na2CO3 s CaCO3 s Na2SO4 s AHof CaSO4 s 501 kJ mol AHo f Na2CO3 s 1130 7 kJ mol AHof CaCO3 s 1206 9 kJ mol AHof Na2SO4 s 1387 1 kJ mol