In photosynthesis, plants form glucose and oxygen from carbon dioxide and water.
6CO_2+6H_2O --> C_6H_12_O_6+6O_2
a) Calculate deltaH rxn at 15 degree C
b) Calculate deltaS rxn at 15
c) Calculate deltaG rxn at 15
thanks!
delta h is 2800
deltaHrxn= 2800kJ
ΔG=2880 kJ
To calculate ΔH (enthalpy change) for the given chemical equation at 15°C, you need to determine the enthalpy change for each reactant and product. The enthalpy change for each substance is represented by ΔHf (standard enthalpy of formation). You can find the values for ΔHf in a reference table or use a chemistry database.
a) To calculate ΔHrxn at 15°C, you need to subtract the sum of the enthalpy changes of the reactants from the sum of the enthalpy changes of the products.
Reactants:
ΔHf(CO2) = -393.5 kJ/mol
ΔHf(H2O) = -285.8 kJ/mol
Products:
ΔHf(C6H12O6) = -1273 kJ/mol
ΔHf(O2) = 0 kJ/mol
Balance the equation and multiply each compound by their respective ΔHf values:
6 × ΔHf(CO2) + 6 × ΔHf(H2O) - [1 × ΔHf(C6H12O6) + 6 × ΔHf(O2)]
6 × (-393.5 kJ/mol) + 6 × (-285.8 kJ/mol) - [1 × (-1273 kJ/mol) + 6 × 0 kJ/mol]
-2361 kJ/mol - (-1273 kJ/mol)
-2361 kJ/mol + 1273 kJ/mol = -1088 kJ/mol
Therefore, the ΔHrxn at 15°C is -1088 kJ/mol.
b) To calculate ΔS (entropy change) for the reaction at 15°C, you need to consider the standard entropy values (ΔSf) for each reactant and product. Again, you can find these values in a reference table or a chemistry database.
Reactants:
ΔSf(CO2) = 213.6 J/(mol·K)
ΔSf(H2O) = 69.9 J/(mol·K)
Products:
ΔSf(C6H12O6) = 212.0 J/(mol·K)
ΔSf(O2) = 205.0 J/(mol·K)
Using the balanced equation, multiply each substance by their respective ΔSf values:
6 × ΔSf(CO2) + 6 × ΔSf(H2O) - [1 × ΔSf(C6H12O6) + 6 × ΔSf(O2)]
6 × (213.6 J/(mol·K)) + 6 × (69.9 J/(mol·K)) - [1 × (212.0 J/(mol·K)) + 6 × (205.0 J/(mol·K))]
1281.6 J/(mol·K) + 419.4 J/(mol·K) - [212.0 J/(mol·K) + 1230 J/(mol·K)]
1701 J/(mol·K) - 1442 J/(mol·K)
259 J/(mol·K)
Therefore, the ΔSrxn at 15°C is 259 J/(mol·K).
c) To calculate ΔG (Gibbs free energy change) for the reaction at 15°C, you need to use the equation:
ΔG = ΔH - TΔS
Where ΔH is the enthalpy change, ΔS is the entropy change, and T is the temperature in Kelvin.
Convert 15°C to Kelvin:
T = 15 + 273.15
T = 288.15 K
Substitute the values into the equation:
ΔG = (-1088 kJ/mol) - (288.15 K × (259 J/(mol·K)))/1000
ΔG = -1088 kJ/mol - 0.074 kJ/mol
ΔG = -1088.074 kJ/mol
Therefore, the ΔGrxn at 15°C is approximately -1088.074 kJ/mol.
Note: The values used in this example are approximate and may vary depending on the specific ΔHf and ΔSf values obtained from a reference source.