Respuesta :
First, we determine the energy released by the reaction using the heat capacity and change in temperature as such:
Q = cΔT
Q = 32.16 * 0.42
Q = 13.51 kJ
Next, we determine the moles of ammonia formed as the heat of formation is expressed in "per mole".
Moles = mass / molecular weight
Moles = 5/17
Moles = 0.294
Heat of formation = 13.51 / 0.294
The heat of formation of ammonia is 45.95 kJ/mol
Q = cΔT
Q = 32.16 * 0.42
Q = 13.51 kJ
Next, we determine the moles of ammonia formed as the heat of formation is expressed in "per mole".
Moles = mass / molecular weight
Moles = 5/17
Moles = 0.294
Heat of formation = 13.51 / 0.294
The heat of formation of ammonia is 45.95 kJ/mol
The heat of formation of ammonia is [tex]\boxed{46.02{\text{ kJ/mol}}}[/tex].
Further Explanation:
Standard enthalpy of formation:
It is the change in enthalpy when one mole of the substance is formed from its constituent elements. It is represented by [tex]\Delta H_{\text{f}}^\circ[/tex].
The given reaction occurs as follows:
[tex]{\text{0}}{\text{.5}}{{\text{N}}_2}\left(g\right)+1.5{{\text{H}}_2}\left(g\right)\to{\text{N}}{{\text{H}}_{\text{3}}}\left(g\right)[/tex]
The formula to calculate the moles of [tex]{\text{N}}{{\text{H}}_{\text{3}}}[/tex] is as follows:
[tex]{\text{Moles of N}}{{\text{H}}_{\text{3}}} = \frac{{{\text{Given mass of N}}{{\text{H}}_{\text{3}}}}}{{{\text{Molar mass of N}}{{\text{H}}_{\text{3}}}}}[/tex] ...... (1)
The given mass of [tex]{\text{N}}{{\text{H}}_{\text{3}}}[/tex] is 5 g.
The molar mass of [tex]{\text{N}}{{\text{H}}_{\text{3}}}[/tex] is 17.03 g/mol.
Substitute these values in equation (1).
[tex]\begin{aligned}{\text{Moles of N}}{{\text{H}}_{\text{3}}}&=\left({5{\text{ g}}}\right)\left({\frac{{{\text{1 mol}}}}{{{\text{17}}{\text{.03 g}}}}}\right)\\&=0.2935{\text{ mol}}\\\end{aligned}[/tex]
The formula to calculate the heat energy of reaction is as follows:
[tex]{\text{Q}}={c\Delta T}}[/tex] …… (2)
Here,
Q is the amount of heat transferred.
c is the specific heat of the substance.
[tex]{\Delta T}}[/tex] is the change in temperature of substance.
The temperature change is to be converted into K. The conversion factor for this is,
[tex]\Delta{\text{T}}\left({^\circ{\text{C}}}\right)=\Delta{\text{T}}\left({\text{K}}\right)[/tex]
So the value of [tex]{\Delta T}}[/tex] becomes 0.42 K.
The value of c is 32.16 kJ/K.
The value of [tex]{\Delta T}}[/tex] is 0.42 K.
Substitute these values in equation (2).
[tex]\begin{aligned}{\text{Q}}&=\left({{\text{32}}{\text{.16 kJ/K}}}\right)\left({{\text{0}}{\text{.42}}\;{\text{K}}}\right)\\&=13.50{\text{72 kJ}}\\\end{aligned}[/tex]
The heat of formation of ammonia is calculated as follows:
[tex]\begin{aligned}\Delta H_{\text{f}}^\circ&=\frac{{{\text{13}}{\text{.5072 kJ}}}}{{0.2935{\text{ mol}}}}\\&=46.0211{\text{ kJ/mol}}\\&\approx{\text{46}}{\text{.02 kJ/mol}}\\\end{aligned}[/tex]
Learn more:
1. What is the final temperature of copper? https://brainly.com/question/7210400
2. Calculate the specific heat of gold: https://brainly.com/question/3032746
Answer details:
Grade: Senior School
Subject: Chemistry
Chapter: Thermodynamics
Keywords: Q, c, 0.42 K, 13.5072 kJ, 46.02 kJ/mol, ammonia, specific heat, heat of formation.
