Question

Consider the reaction 2H₂O(l)-------->2H₂(g)+O₂(g) Calculate the work done at 25 degree Celsius for the decomposition of 36 ml of water?

a)1.788kCal
b)2.576kCal
c)-1.788kCal
d)-2.576kCal

Answer 1

The decomposition of 36 ml of water requires an input of energy, which corresponds to the negative work done by the system. When converting the required energy into kcal, the result is -115.133252 kcal, which does not match the given options, indicating a possible mistake in the question or the answer choices.

Step-by-step explanation:

When considering the reaction 2H₂O(l) → 2H₂(g) + O₂(g) and calculating the work done at 25 degrees Celsius for the decomposition of 36 ml of water, we need to consider the enthalpy change of the reaction. We know that for the formation of 2 moles of gaseous water from hydrogen and oxygen gases, 482 kJ of heat is released according to the reaction 2H₂(g) + O₂(g) = 2H₂O(g). However, we are dealing with the reverse reaction, which requires inputting this amount of energy to dissociate the water into hydrogen and oxygen gases.

Firstly, we determine the number of moles of water we have. The density of water is approximately 1 g/ml, so 36 ml of water weighs about 36 grams. The molar mass of water is approximately 18 g/mol. Therefore, we have 36 g / 18 g/mol = 2 moles of water. Considering the reaction requires 482 kJ of energy per 2 moles of water decomposed, we have 482 kJ for the 2 moles provided.

To convert kJ to kcal, we use the conversion factor 1 kJ = 0.239006 kcal. Thus, the energy required for the decomposition of 36 ml of water is 482 kJ * 0.239006 kcal/kJ = 115.133252 kcal. However, since work is done by the system (energy input), this value is negative: -115.133252 kcal. This value doesn't correspond to any of the answer choices provided, suggesting a potential error in the question or answer choices.

Answer 2

The work done during the decomposition of 36 ml of water at 25 degrees Celsius cannot be determined without the external pressure and change in volume values.

This correct answer is none of the above.

Step-by-step explanation:

To calculate the work done (w) during the decomposition of water, we can use the equation:

w=−PextΔV

where Pext is the external pressure and ΔV is the change in volume. The negative sign indicates work done on the system (compression) when w is negative.

First, we need to convert the given volume of water (36ml) to moles using the molar volume of water at standard temperature and pressure (STP), which is 22.4L/mol.

Volume of water (in L)= 36ml/ 1000ml/L

Now, let's calculate the moles of water:

Moles of water = Volume of water / Molar volume of water at STP

Next, use the balanced chemical equation to find the moles of gas produced (in this case, H2):

2moles of water→2moles of H2

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Since the reaction is at 25 degrees Celsius, it's not at standard conditions (0 degrees Celsius). Therefore, we need to consider the non-ideal behavior of gases and use the Van der Waals equation to calculate the pressure (P).

Finally, use the work equation to find the work done:

w=−PextΔV

The negative sign in the result indicates work done on the system.

Unfortunately, without the specific values for the external pressure and the change in volume, I cannot provide the exact numerical answer. Please provide the necessary values, and I can help you with the calculation.

This correct answer is none of the above.