how many Kj of heat are evolved when 6g of pure carbon is completely burned? how many grams of carbon must be burned to furnish 39.3 kJ of heat. enthalpy of combustion of carbon is -393.5
C + O2 ==> CO2
393.5 kJ x (6g/12g) = kJ heat released to burn 6g C.
X grams C = 12 x (39.3/393.5) =
To calculate the amount of heat evolved during the combustion of carbon, you can use the equation:
q = n * ΔH
Where:
q is the heat evolved (in kJ)
n is the moles of carbon burned
ΔH is the enthalpy of combustion of carbon (in this case, -393.5 kJ/mol)
First, let's calculate the moles of carbon in 6 g:
1) Calculate the molar mass of carbon (C):
C: 12.01 g/mol
2) Calculate moles using the molar mass:
moles = mass / molar mass
moles = 6 g / 12.01 g/mol
moles ≈ 0.4996 mol
Now we can calculate the heat evolved:
q = n * ΔH
q = 0.4996 mol * -393.5 kJ/mol
q ≈ -196.77 kJ (rounded to two decimal places)
So, when 6 g of pure carbon is completely burned, approximately -196.77 kJ of heat is evolved.
To find out how many grams of carbon must be burned to furnish 39.3 kJ of heat, you can rearrange the equation:
q = n * ΔH
n = q / ΔH
n = 39.3 kJ / -393.5 kJ/mol
n ≈ -0.0999 mol
Now, we can calculate the mass of carbon:
mass = n * molar mass
mass = -0.0999 mol * 12.01 g/mol
mass ≈ -1.196 g (rounded to three decimal places)
The negative sign indicates that the mass is not physically meaningful in this context. It suggests that you would need to supply energy to the system rather than extract heat from it to achieve a positive heat transfer of 39.3 kJ.
To calculate the amount of heat evolved when a given mass of a substance is burned, you need to use the concept of molar mass and the enthalpy of combustion. Here's how you can do it:
1. Calculate the number of moles of carbon in 6 grams:
- The molar mass of carbon (C) is 12.01 g/mol.
- Number of moles = Mass / Molar mass
- Number of moles = 6 g / 12.01 g/mol = 0.499 moles
2. Use the balanced equation for the combustion of carbon:
C(s) + O2(g) -> CO2(g)
From the equation, you can see that one mole of carbon is required to produce one mole of CO2.
3. Calculate the amount of heat evolved when 0.499 moles of carbon are burned:
- The enthalpy of combustion of carbon is given as -393.5 kJ/mol.
- Heat evolved = Number of moles × Enthalpy of combustion
- Heat evolved = 0.499 moles × -393.5 kJ/mol = -196.3 kJ (negative sign indicates heat being evolved)
Therefore, when 6 grams of pure carbon is completely burned, around 196.3 kJ of heat is evolved.
Now, let's calculate the grams of carbon required to furnish 39.3 kJ of heat:
1. Rearrange the equation to solve for moles:
Heat evolved = Number of moles × Enthalpy of combustion
Number of moles = Heat evolved / Enthalpy of combustion
2. Substitute the given values:
Number of moles = 39.3 kJ / -393.5 kJ/mol = -0.100 moles (negative sign indicates heat being evolved)
3. Calculate the mass of carbon:
Mass = Number of moles × Molar mass
Mass = -0.100 moles × 12.01 g/mol = -1.201 g (negative sign indicates the mass is not physically possible)
Since the calculated mass is negative, it suggests that you cannot burn a negative mass of carbon to furnish 39.3 kJ of heat. Please review any data input or sources to ensure accuracy.