4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g)
If standard enthalpy change is -906.2 kJ, what quantity of heat is evolved or absorbed in the formation of 17.0 g of NH3?
906.2 kJ heat is evolved for the formation of 4 moles NH3 (4*17 g NH3). So how much heat is evolved for 17.0 g?
I'm still a bit confused... I don't know where to start. What does 4*17g NH3 mean??
To find the quantity of heat evolved or absorbed in the formation of 17.0 g of NH3, we can use the equation
ΔH = q / n
where ΔH is the standard enthalpy change, q is the quantity of heat evolved or absorbed, and n is the number of moles of NH3 formed.
First, we need to calculate the number of moles of NH3 formed from 17.0 g.
1 mole of NH3 has a molar mass of:
N = 14.01 g/mol
H = 1.01 g/mol
3H = (3 x 1.01) g/mol
Total molar mass of NH3 = 14.01 + (3 x 1.01) = 17.04 g/mol
Number of moles of NH3 formed = mass / molar mass = 17.0 g / 17.04 g/mol = 0.997 mol (rounded to three decimal places)
Now, we can use the equation ΔH = q / n to find the quantity of heat evolved or absorbed.
ΔH = -906.2 kJ (given)
n = 0.997 mol (calculated)
q = ΔH * n
q = -906.2 kJ * 0.997 mol
q = -903.3 kJ (rounded to three decimal places)
Therefore, the quantity of heat evolved or absorbed in the formation of 17.0 g of NH3 is approximately -903.3 kJ.
To determine the quantity of heat evolved or absorbed in the formation of 17.0 g of NH3, you need to use stoichiometry and the standard enthalpy change given.
First, calculate the molar mass of NH3:
Molar mass of NH3 = 1(1) + 3(1) = 17.0 g/mol
Next, use this molar mass to convert the given mass of NH3 to moles:
Number of moles of NH3 = 17.0 g / 17.0 g/mol = 1 mol
Now, you can apply stoichiometry to relate the moles of NH3 to the quantity of heat evolved or absorbed.
From the balanced equation, you can see that 4 moles of NH3 react to produce -906.2 kJ of heat. This means that one mole of NH3 produces -906.2 kJ / 4 mol = -226.6 kJ of heat.
Since you have 1 mole of NH3, the quantity of heat evolved or absorbed is:
Quantity of heat = -226.6 kJ
Therefore, when 17.0 g of NH3 reacts, -226.6 kJ of heat is evolved or absorbed.