Temperature

TEMPERATURE and ∆H

• - The effect of a change in temperature on a equilibrium system is determined by the sign of the enthalpy change ∆H for the reaction.
• - This is because from the ∆H we can tell if the reaction is endothermic or exothermic..
• An exothermic reaction releases heat and has a -∆H
• An enothermic reaction absorbs heat and has a +∆H
• -The ∆H given for any reaction is always for the forward reaction (-->)
• - If the reaction is exothermic in one direction it will be endothermic the other.
• *NOTE* You will find the ∆H by the equation in the question.

What if the temperature is changed...?

• DECREASING THE TEMPERATURE:
• Equilibrium shifts in the direction of the exothermic reaction (releasing heat) to increase the temperature
• INCREASING THE TEMPERATURE:
• Equilibrium shifts in the direction of the endothermic reaction (absorbing heat) to decrease the temperature.

Examples:

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• Bildunterschrift: iF YOU INCREASE THE TEMPERATURE IT WILL MOVE TO THE LEFT BECAUSE THE LEFT IS THE ENDOTHERMIC REACTION, SO THE TEMPERATURE WILL DECREASE (AS ENDOTHERMIC REACTIONS ABSORB HEAT - IT WILL TAKE HEAT AWAY FROM THE REACTION)
• Bildunterschrift: iF YOU DECREASE THE TEMPERATURE IT WILL MOVE TO THE RIGHT BECAUSE THE RIGHT IS THE EXOTHERMIC REACTION, SO THE TEMPERATURE WILL INCREASE (AS EXOTHERMIC REACTIONS RELEASE HEAT - IT WIL GIVE HEAT TO THE REACTION)