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For the reaction C(6)H(12)(l)+9O(2)(g)...

For the reaction
`C_(6)H_(12)(l)+9O_(2)(g)to6H_(2)O(l)+6CO_(2)(g)` , `DeltaH=-936.9kcal`
Which of the following is true ?

A

`-936.9 = Delta E - (2 xx10^(-3) xx298 xx3) kcal`

B

`+936.9 = Delta E + (2 xx10^(-3) xx298 xx3) kcal`

C

`-936.9 = Delta E - (2 xx10^(-3) xx298 xx2) kcal`

D

`-936.9 = Delta E + (2 xx10^(-3) xx298 xx2) kcal`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the given reaction and the relationship between the change in enthalpy (ΔH) and the change in internal energy (ΔE). The reaction is: \[ C_{6}H_{12}(l) + 9O_{2}(g) \rightarrow 6H_{2}O(l) + 6CO_{2}(g) \] Given: - ΔH = -936.9 kcal ### Step 1: Understand the relationship between ΔH and ΔE The relationship between the change in enthalpy (ΔH) and the change in internal energy (ΔE) is given by the equation: \[ \Delta H = \Delta E + \Delta N_g RT \] Where: - ΔN_g = change in the number of moles of gas (moles of gaseous products - moles of gaseous reactants) - R = gas constant - T = temperature in Kelvin ### Step 2: Calculate ΔN_g To find ΔN_g, we need to count the moles of gaseous products and reactants: - **Products**: 6 moles of \( CO_{2}(g) \) (6 moles of gas) - **Reactants**: 9 moles of \( O_{2}(g) \) (9 moles of gas) Now, calculate ΔN_g: \[ \Delta N_g = \text{(moles of gaseous products)} - \text{(moles of gaseous reactants)} = 6 - 9 = -3 \] ### Step 3: Use the gas constant R The gas constant R in kcal is: \[ R = 2 \times 10^{-3} \text{ kcal/K/mol} \] ### Step 4: Use the temperature T Assuming standard temperature, T = 298 K. ### Step 5: Substitute values into the equation Now, substitute the values into the relationship: \[ -936.9 \text{ kcal} = \Delta E + (-3) \times (2 \times 10^{-3} \text{ kcal/K/mol}) \times 298 \text{ K} \] Calculating the right side: \[ -3 \times (2 \times 10^{-3}) \times 298 = -3 \times 0.002 \times 298 = -1.788 \text{ kcal} \] ### Step 6: Rearranging the equation to find ΔE Now, we can rearrange the equation to solve for ΔE: \[ -936.9 = \Delta E - 1.788 \] Adding 1.788 to both sides: \[ \Delta E = -936.9 + 1.788 = -935.112 \text{ kcal} \] ### Conclusion Thus, the change in internal energy (ΔE) for the reaction is approximately -935.112 kcal.
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