Substance l\'i kJ/mol S\" J/mol K C (G) co2(g) H2 0) H20 0) 02() 5 2136 130.6 69
ID: 575267 • Letter: S
Question
Substance l'i kJ/mol S" J/mol K C (G) co2(g) H2 0) H20 0) 02() 5 2136 130.6 69.91 205.0 2263 -3935 285.85 1. When 250 grams of butyric and, CaH-COOH is completely combusted at CO2 (g) and H2O (1) are formed with the evolution of 60.0 k (a) Caleulate the molar heat of combustion for butyric acid (b) Write a balanced thermochemical equation for the molar heat of combustion for butyric acid. (e) Calculate the standard tree energy of combustion, AG'f, for butyric acid at 25 c (d) If 5.00 what vrill be the heat s of butyric acid is combusted in a bomb calorimeter capacity of the bomb if the temperature of the bomb goes from 25.0C to 300C surrounded by 1.912 kg of water at 25'C, what will be the final temperature ot te) I5.00 g of butyric acid is combusted in the part (d) bomb calorimeter that is ic heat of water is 4.164 J/g-C the system? The sl butyric acid butyric acid at 25'C. Calculate the standard free energy of formation, AG"f, for butyric acid at 25 compared to the molar heat of formation for H20 (07 Explain. 20.0 grams of butyric acid. Air is 20.0 percent by volume oxygen. (From the data at the top, caleulate the standard heat of fomration, AH't. for r (g) Wnte a balanced thermochemical equation for the molar heat of formation for (h) Calcualte the standard entropy change, AS't, for the formation of butyric acid (i) () Would the molar heat of formation for H20 (g) be (more, less, or the same) when V (k) Calculate the volume of air at 25'C and 750. mmHg that is needed to combust when liquid water is introduced into an evacuated vessel at 25°C some of the water vaporizes. Predict how the enthalpy, entropy, free energy, and temperature change in the system during 2 (a) this process. Explain the basis for each of your predictions when a large amount of ammonium chloride is added to water at 25C, some of it dissolves and the temperature of the system decreases. Preidct how the enthalpy, entropy, and free energy change in the system during this process. Explain the basis for each of your predictions. (b) (c) If the temperature of the aqueous ammonium chloride system in part (b) were to be increased to 30C, predict how the solubility of the ammonium chloride would be affected. Explain the basis for each of your predictions.Explanation / Answer
a) Molar mass of butyric acid is 88.11g / mole
Heat evolved from combustion of 2.5 grams = 60kJ
So heat evolved from combustion of 1 gram = 60 /2.5 kJ
Heat evolved from combustion of 88.11grams (one mole) = Molar heat of combustion = 60 X 88.11 / 2.5 = 2114.64 kJ
b) Balanced equation will be
C3H7COOH + 5O2 ---> 4CO2 (g) +4H2O (l)
c) Srxn = sum of S(prodcuts) - sum of S (reactants)
Srxn = [4 XS CO2 + 4 X S H2O) - (S C3H7COOH + 5S O2)
= [4 X 213.6 + 4 X 69.91] - [226.3 + 5 X 205] = -117.26 J / mole K = -0.11726 kJ / mol K
Hrxn = -2114.64 kJ / mole
Grxn = Hrxn - TS = -2114.64 - 298 X (-0.11726) = -2079.7 kJ / mole
d) The heat evolved by burning of 5g of butyric acid = 2X 60kJ = 120 kJ [as heat evolved from 2.5g was 60kJ)
This heat will raise the temperature as
Heat = Heat capacity of calorimeter X change in temperature
120 X 1000 Joules = heat capacity X (30-25)
Heat capacity = 24 kJ / 0C