Answer:
-2247 kJ.
Step-by-step explanation:
If you want to calculate the free energy change of a reaction at 25 ∘C, you need to follow these simple steps:
- 1. Add 273.15 to the temperature in degrees Celsius to get the temperature in kelvins. This is because 0 K is the absolute zero, where all molecular motion stops. For example, 25 ∘C + 273.15 = 298.15 K. Don't ask me why it's not 273.16 or 273.14, it's just one of those things that scientists agreed on.
- 2. Divide the entropy change in joules per kelvin by 1000 to get the entropy change in kilojoules per kelvin. This is because joules are too small and kilojoules are more convenient. For example, 101.1 J/K ÷ 1000 = 0.1011 kJ/K. Don't ask me why it's not 100 or 10, it's just another one of those things that scientists agreed on.
- 3. Multiply the temperature in kelvins and the entropy change in kilojoules per kelvin to get the second term of the formula. This is because entropy is a measure of disorder and temperature is a measure of heat, and disorder and heat are related somehow. For example, 298.15 K × 0.1011 kJ/K = 30.14 kJ. Don't ask me why it's not 30.13 or 30.15, it's just one of those things that calculators agreed on.
- 4. Subtract the second term from the enthalpy change in kilojoules to get the free energy change in kilojoules. This is because enthalpy is a measure of heat and work, and free energy is a measure of how much work can be done by a reaction. For example, -2217 kJ - 30.14 kJ = -2247.14 kJ. Don't ask me why it's not -2247.13 or -2247.15, it's just one of those things that math agreed on.
- 5. Round the answer to an appropriate number of significant figures. This is because significant figures are a way of showing how precise your measurements are, and you don't want to overstate or understate your precision. For example, since the given values have four significant figures each, the answer should also have four significant figures. Therefore, ΔG∘rxn = -2247 kJ.
- 6. The negative sign of ΔG∘rxn indicates that the reaction is spontaneous at 25 ∘C. This means that the reaction will happen by itself without any external input or intervention. For example, if you mix baking soda and vinegar, you will get a spontaneous reaction that produces bubbles and heat. Don't ask me why it's not positive or zero, it's just one of those things that nature agreed on.
Congratulations! You have successfully calculated the free energy change of a reaction at 25 ∘C using some basic chemistry concepts and formulas. Now you can impress your friends and family with your newfound knowledge and skills!