H2(g) + Cl2(g) → 2HCl(g) ΔH = −184.6 kJ/mol. If 3.00 moles of H2 react with 3.00 moles of Cl2 to form HCl, what is ΔU (in kJ) for this reaction at 1.0 atm and 25°C? Assume the reaction goes to completion

Respuesta :

Answer : The value of [tex]\Delta E[/tex] of the reaction is, -553.8 KJ

Explanation :

Formula used :

[tex]\Delta E=\Delta H-\Delta n_g\times RT[/tex]

where,

[tex]\Delta E[/tex] = internal energy of the reaction = ?

[tex]\Delta H[/tex] = enthalpy of the reaction = -184.6 KJ/mole = -184600 J/mole

The balanced chemical reaction is,

[tex]H_2(g)+Cl_2(g)\rightarrow 2HCl(g)[/tex]

when the moles of [tex]H_2\text{ and }Cl_2[/tex] are 3 moles then the reaction will be,

[tex]3H_2(g)+3Cl_2(g)\rightarrow 6HCl(g)[/tex]

From the given balanced chemical reaction we conclude that,

[tex]\Delta n_g[/tex] = change in the moles of the reaction = Moles of product - Moles of reactant = 6 - 6 = 0 mole

R = gas constant = 8.314 J/mole.K

T = temperature = [tex]25^oC=273+25=298K[/tex]

Now put all the given values in the above formula, we get:

[tex]\Delta E=(-184600J/mole\times 3mole)-(0mole\times 8.314J/mole.K\times 298K)[/tex]

[tex]\Delta E=-553800J[/tex]

[tex]\Delta E=-553.8KJ[/tex]

Therefore, the value of [tex]\Delta E[/tex] of the reaction is, -553.8 KJ

The enthalpy of the reaction = The change in internal energy of the

reaction

The change in the internal energy for the reaction, ΔU is -553.8 kJ/mol.

Reasons:

The given parameters are;

Chemical reaction;

H₂(g) + Cl₂(g) → 2HCl(g)

ΔH for the reaction = -184.6 kJ/mol

Number of moles of H₂ = 3.00 moles

Number of moles of Cl₂ = 3.00 moles

Required:

ΔU (in kJ) for the reaction

Solution:

The pressure and temperature for the reaction = 1.0 atm, and 25°C, which

are the standard temperature and pressure.

The reaction is presented as follows;

3H₂(g) + 3Cl₂(g) → 6HCl(g)

The number of moles in the reactant and product are multiplied by 3,

therefore, ΔH = 3 × -184.6 kJ/mol = -553.8 kJ/mol

The change in the number of moles of gas, [tex]\Delta n_g[/tex], is given as follows;

[tex]\Delta n_g[/tex] = [tex]n_{final} - n_{initial}[/tex]

The number of moles of gas in the reactants, [tex]n_{initial}[/tex] = 6 moles

The number of moles of gas in the final product, [tex]n_{final}[/tex] = 6 moles

∴ [tex]\Delta n_g[/tex] = 6 - 6 = 0

ΔH = ΔU + [tex]\Delta n_g[/tex]·R·T

Which gives;

ΔH = ΔU + 0×R×T  = ΔU

ΔH = -553.8 kJ/mol. = ΔU

ΔU = -553.8 kJ/mol.

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