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3 years ago

A reaction is non-spontaneous at any temperature when

Chemistry

1 answer:

slavikrds [6]3 years ago

8 0

Answer:

A reaction is non-spontaneous at any temperature when the Gibbs free energy > 0.

Explanation:

There is a state function, that determines if a reaction is sponaneous or non spontaneous:

ΔG = Gibbs free energy

A reaction is non spontaneous when it does require energy to produce that reaction. It will be spontaneous, when the reaction does not require energy to be occured.

The formula is: ΔG = ΔH - T.ΔS

ΔH → Enthalpy → Energy gained or realeased as heat.

ΔH < 0 → <em>Exothermic reaction. Spontaneity is favored </em>

T → Temperature

ΔS → Entropy → Degree of disorder of a system.

When the system has a considered disorder ΔS > 0, disorder increases.

When the system is more ordered, ΔS < 0, disorder decreases.

The reaction will be non spontaneous if, the enthalpy is positive (endothermic reaction) and the ΔS < 0 (disorder decreases). It will not occur if we do not give energy.

ΔG < 0 → Spontaneous reaction

ΔG > 0 → Non spontaneous reaction

ΔG = 0 → System in equilibrium

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3 years ago

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3 years ago

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yawa3891 [41]

Explanation:

Since HF is a weak acid, the use of an ICE table is required to find the pH. The question gives us the concentration of the HF.

HF+H2O⇌H3O++F−HF+H2O⇌H3O++F−

Initial0.3 M-0 M0 MChange- X-+ X+XEquilibrium0.3 - X-X MX M

Writing the information from the ICE Table in Equation form yields

6.6×10−4=x20.3−x6.6×10−4=x20.3−x

Manipulating the equation to get everything on one side yields

0=x2+6.6×10−4x−1.98×10−40=x2+6.6×10−4x−1.98×10−4

Now this information is plugged into the quadratic formula to give

x=−6.6×10−4±(6.6×10−4)2−4(1)(−1.98×10−4)−−−−−−−−−−−−−−−−−−−−−−−−−−−−√2x=−6.6×10−4±(6.6×10−4)2−4(1)(−1.98×10−4)2

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However we can rule out x=-0.014405 because there cannot be negative concentrations. Therefore to get the pH we plug the concentration of H3O+ into the equation pH=-log(0.013745) and get pH=1.86

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