The complete combustion of butane, (g) is represented by the equation
C4H10+13/2O2->4CO2+5H20
STANDARD ENTHALPY IS -2877KJ/MOL
How much heat, in kilojoules, is evolved in the complete combustion of
12.8L C4H10 at 23.8degrees celsius and 744mmhg ?
To find the amount of heat evolved in the complete combustion of 12.8 L of butane (C4H10) at 23.8 degrees Celsius and 744 mmHg, we need to use the ideal gas law, along with the molar enthalpy change.
Step 1: Convert the volume to moles
To convert the volume of butane gas to moles, we need to use the ideal gas law equation:
PV = nRT
Where:
P = pressure in atm
V = volume in liters
n = moles of gas
R = ideal gas constant (0.0821 L.atm/mol.K)
T = temperature in Kelvin
First, we need to convert the given temperature to Kelvin by adding 273.15:
T = 23.8 + 273.15 = 297.95K
Next, we need to convert the given pressure from mmHg to atm:
P = 744 mmHg * (1 atm / 760 mmHg) = 0.97947 atm
Now we can calculate the number of moles of butane gas:
12.8 L * 0.97947 atm = n * 0.0821 L.atm/mol.K * 297.95 K
n = (12.8 L * 0.97947 atm) / (0.0821 L.atm/mol.K * 297.95 K)
n = 0.57125 mol
Step 2: Calculate the heat evolved
The molar enthalpy change during the combustion of butane is given as -2877 kJ/mol.
Since you have 0.57125 mol of butane, you can now calculate the heat evolved:
Heat evolved = molar enthalpy change * moles
Heat evolved = -2877 kJ/mol * 0.57125 mol
Heat evolved = -1644.51 kJ
Therefore, in the complete combustion of 12.8 L of butane at 23.8 degrees Celsius and 744 mmHg, approximately 1644.51 kJ of heat is evolved.
To find the amount of heat evolved in the complete combustion of 12.8L of butane (C4H10) at 23.8 degrees Celsius and 744 mmHg, you need to follow these steps:
Step 1: Convert the given volume of butane to moles.
To do this, you need to use the ideal gas law equation, which is:
PV = nRT
Where:
P = pressure (744 mmHg)
V = volume in liters (12.8 L)
n = number of moles
R = ideal gas constant (0.0821 L·atm/mol·K)
T = temperature in Kelvin (23.8 degrees Celsius + 273.15)
Let's calculate the number of moles of butane:
PV = nRT
(744 mmHg)(12.8 L) = n(0.0821 L·atm/mol·K)(23.8 degrees Celsius + 273.15)
Convert mmHg to atm:
1 atm = 760 mmHg
744 mmHg = 744/760 atm
(744/760 atm)(12.8 L) = n(0.0821 L·atm/mol·K)(23.8 + 273.15)
0.996 atm·L = n(0.0821 L·atm/mol·K)(297.95 K)
Divide both sides by (0.0821 L·atm/mol·K)(297.95 K) to solve for n:
n = (0.996 atm·L) / (0.0821 L·atm/mol·K)(297.95 K)
Calculate the value of n.
Step 2: Use the stoichiometry from the balanced equation to find the heat evolved.
From the balanced equation: C4H10 + 13/2 O2 -> 4 CO2 + 5 H2O
The stoichiometric coefficient of C4H10 is 1, and the stoichiometric coefficient of CO2 is 4.
Since the equation states that the standard enthalpy change for the combustion of 1 mole of C4H10 is -2877 kJ, we can use the stoichiometry to calculate the heat evolved for the given number of moles of C4H10.
Multiply the number of moles of C4H10 by the standard enthalpy change to find the heat evolved:
Heat evolved = (number of moles of C4H10) × (standard enthalpy change)
Calculate the value of heat evolved.
Remember to round your final answer to the appropriate number of significant figures based on the given data.