A certain first-order reaction has a rate constant of 2.75 10-2 s−1 at 20.°c. what is the value of k at 45°c if ea = 75.5 kj/mol? webassign will check your answer for the correct number of significant figures. 0.0352 incorrect: your answer is incorrect.

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Answer:

0.314 s⁻¹  

Step-by-step explanation:

Use the Arrhenius equation.

[tex]\ln( \frac{k_2 }{k_1 }) = (\frac{E_{a} }{R })(\frac{ 1}{T_1} - \frac{1 }{T_2 })\\[/tex]

Data:

k₁ = 0.0275 s⁻¹;            k₂ = ?

Eₐ = 75.5 kJ·mol⁻¹

T₁ = 20 °C = 293.15 K; T₂ = 45°C = 318.15 K

Calculation:

[tex]\ln(\frac{k_{2} }{0.0275}) = (\frac{75 500 }{8.314})(\frac{ 1}{293.15} - \frac{1 }{318.15 })[/tex]

[tex]\ln(\frac{k_{2} }{0.0275}) = 9081\times 2.681 \times10^{-4}[/tex]

[tex]\ln(\frac{k_{2} }{0.0275}) = 2.434[/tex]

[tex]\frac{k_{2} }{0.0275} = \text{e}^{2.434}[/tex]

[tex]\frac{k_{2} }{0.0275} = 11.41[/tex]

k₂ = 0.0275 × 11.41

k₂ = 0.314 s⁻¹

The value of [tex]k[/tex] (rate constant) will be 0.314 s⁻¹  at 45°C if activation energy is 75.5 kJ/mol.

What does the Arrhenius equation tell?

It describes the effect of temperature change on the rate of reaction.

[tex]{\rm ln}\dfrac{k_2}{k_1} = (\dfrac {E_a}{R}){\dfrac 1{T_1}} - \dfrac 1{T_2}}[/tex]

Where,

k₁ - rate constant = 0.0275 s⁻¹            

k₂ = ?

Eₐ - Activation energy = 75.5 kJ·mol⁻¹

T₁- Initial temperature = 20 °C = 293.15 K

T₂- Final temperature = 45°C = 318.15 K

Put the values in the formula,

[tex]{\rm ln}\dfrac{k_2}{0.0275} = (\dfrac {75.5}{8.314}){\dfrac 1{293.15 }} - \dfrac 1{318.15}}\\\\K_2 = 0.314[/tex]

Therefore, the value of [tex]k[/tex] (rate constant) will be 0.314 s⁻¹  at 45°C if activation energy is 75.5 kJ/mol.

Learn more about Arrhenius equation:

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