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Chapter 3: Problem 14

Determine the adiabatic, stoichiometric flame temperature at constant pressure for n-butanol, an alternative biofuel, give \((25 \mathrm{C}, 1 \mathrm{~atm})\) the enthalpy of combustion is \(-26\)

Short Answer

Expert verified
Answer: To find the adiabatic stoichiometric flame temperature for n-butanol, you must follow these steps: 1. Calculate the initial moles of each species involved in the combustion (1 mole n-butanol, 6 moles O2, 0 moles CO2, and 0 moles H2O). 2. Determine the initial enthalpy of the reactants using the provided specific heat values and initial temperature. 3. Calculate the final enthalpy of the products using the given enthalpy of combustion and initial enthalpy of reactants. 4. Determine the final moles of each species involved in the combustion (0 moles n-butanol, 0 moles O2, 4 moles CO2, and 5 moles H2O). 5. Use an energy balance equation and final enthalpy of products to calculate the final temperature. 6. The adiabatic stoichiometric flame temperature is the final temperature calculated in step 5.

Step by step solution

01

Calculate initial moles of each species involved in the combustion

From the stoichiometric equation, 1 mole of n-butanol reacts with 6 moles of O2 to produce 4 moles of CO2 and 5 moles of H2O. So, initially, we have: - 𝑛𝑏𝑢𝑡𝑎𝑛𝑜𝑙,0 = 1 mole - 𝑛𝑂2,0 = 6 moles - 𝑛𝐶𝑂2,0 = 0 moles - 𝑛𝐻2𝑂,0 = 0 moles
02

Determine the initial enthalpy of the reactants

The initial enthalpy of the reactants can be calculated using the given specific heat values and initial temperature (25°C or 298.15 K): \(H_{reactants, initial} = (1.1\times 1 \times (298.15))+ (1.0\times 6 \times (298.15))\)
03

Calculate the final enthalpy of the products

The enthalpy of combustion is equal to the difference in enthalpy between products and reactants. Rearranging and using the given enthalpy of combustion (-26 kJ/g): \( H_{products, final} = H_{reactants, initial} + \Delta H_{combustion}\)
04

Determine the final moles of each species involved in the combustion

After the reaction, we have: - 𝑛𝑏𝑢𝑡𝑎𝑛𝑜𝑙,final = 0 moles - 𝑛𝑂2,final = 6 - 6 = 0 moles - 𝑛𝐶𝑂2,final = 4 moles - 𝑛𝐻2𝑂,final = 5 moles
05

Calculate final temperature

Use energy balance (with Q = 0) and final enthalpy of products to determine the final temperature: \(H_{products,final} = H_{CO2,final} + H_{H2O,final} = (1.0 \times 4 \times (T_{final}))+ (1.0 \times 5 \times (T_{final}))\) Solve for \(T_{final}\).
06

Obtain adiabatic stoichiometric flame temperature

The adiabatic stoichiometric flame temperature is the final temperature calculated in Step 5. This value represents the flame temperature under adiabatic conditions, presuming the reaction goes to completion, and considering only the major species involved in the combustion process.

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Most popular questions from this chapter

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