Question

A mole of X reacts at a constant pressure of 43.0 atm via the reaction X(g)+4Y(g)→2Z(g), ΔH∘=−75.0 kJ Before the reaction, the volume of the gaseous mixture was 5.00 L. After the reaction, the volume was 2.00 L. Calculate the value of the total energy change, ΔE, in kilojoules.

Answer 1

The value of the total energy change, ΔE, in kilojoules = -61.93 kJ

Further explanation

Thermochemistry is a branch of chemistry that studies heat changes in chemical reactions.

Thermochemistry is the application of thermodynamics to chemistry.

Thermochemistry is used to predict energy changes in:

• 1. chemical reaction
• 2. change in form
• 3. solution

Energy in (E) is the energy contained in a material

Internal energy is affected by heat changes and work (w)

Delta H reaction (ΔH) is the amount of heat change between the system and its environment

(ΔH) can be positive (endothermic = requires heat) or negative (exothermic = releasing heat)

Enthalpy (H) is a state function which is the sum of the Energy in (E) and work (w).

At constant pressure (P = fixed), the change in entalphy can be formulated:

ΔH = ΔE + P. ΔV

$\large{\boxed{\bold{\Delta E=\Delta H-P.\Delta V}}}$

From the problem it can be seen that

ΔH = -75.0 kJ

Pressure, P = 43.0 atm

= 43 atm x 1,01325 .10⁵ Pa / atm

= 4,357.10⁶ Pa

= 4,357.10⁶ N / m²

Volume changes that occur

ΔV = 2.0 L - 5.0 L

= -3.0 L

= -3.0 x 10⁻³ m³

= 1.3071.10⁴ J

= 13,071 kJ

So that:

ΔE = ΔH - PΔV

ΔE = -75.0 kJ - (4,357.10⁶ .- 3.0 x 10⁻³ m3)

ΔE = -75.0 kJ + 13,071 kJ

ΔE = -61.93 kJ

Learn more

Delta H solution

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an exothermic reaction

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 as endothermic or exothermic

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an exothermic dissolving process

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Keywords: exothermic, endothermic, enthalpy, internal energy, heat