I don't understand the effect of temperature on a reaction. For exmaple:
CO + 3H2 <-> CH4 + H2O deltaH= -230 KJ
If there were an increase in temperature then the CH4 and H2O would have a harding time becoming the CO and H2 so therefore the reaction would move to the right. Is that right?
Here is a tip. Always replace the -delta H or + delta H like this.
CO + 3H2 <==>CH4 + H2O + heat (if delta H were + it means the reaction is endothermic instead of exothermic and I would have written heat on the left side with the reactants. Now that the heat is placed properly, just answer as you would for any change in concentration of the molecules. So adding heat to the reacting makes the reaction shift so as to use up the heat and that means the reaction shifts to the left. (You see that CH4 + H2O + heat makes the reactants and heat is used to do that so the reaction moves to the left.)
Ohh wow, what an awesome tip! Thank you so much. This was so confusing until now :D
So for something like (losing heat)
2A + B <-> 2C delta H postive
it would be
2A + B <-> 2C -heat
the reaction would move right?
Yes, but since negative signs can be confusing, I would write it as
2A + B + heat <==> 2C, then adding heat makes the reaction shift to the right. That way the rules I follow stay the same; i.e., it moves AWAY from what is being added. So adding A or B or heat would make it move to the right; adding C or cooling it would make it move to the left
Thank You :)
Yes, you're on the right track! An increase in temperature can indeed affect the direction of a chemical reaction. In the reaction you mentioned, CO + 3H2 ↔ CH4 + H2O, an increase in temperature would cause the reaction to shift towards the right side, favoring the production of CH4 and H2O.
To understand how temperature affects a reaction, you can consider it in terms of collision theory. According to collision theory, for a reaction to occur, reactant molecules must collide with each other with sufficient energy (activation energy) and the right orientation.
When you increase the temperature, you're essentially increasing the average kinetic energy of the molecules. As a result, the reactant molecules move faster and collide more frequently. Additionally, the increased kinetic energy means that a greater proportion of collisions possess the required activation energy for the reaction to take place.
So, in your reaction, if you increase the temperature, it will provide more energy to the reactant molecules. This results in an increased number of successful collisions and a higher rate of reaction towards the production of CH4 and H2O. The reaction shifts to the right because the forward reaction consumes more heat energy (exothermic) and is favored at higher temperatures.
It's important to note that the effect of temperature on a reaction also depends on the enthalpy change (∆H) of the reaction. In your example, the reaction is exothermic (releases heat energy), indicated by the negative value of ∆H (-230 KJ). Exothermic reactions are favored at lower temperatures and their equilibrium shifts to the right with increasing temperature.
Conversely, endothermic reactions (absorb heat energy) are favored at higher temperatures, and their equilibrium shifts to the left with increasing temperature. The sign of ∆H (+/-) plays a crucial role in determining the effect of temperature on the direction of a reaction.
Overall, an increase in temperature can make the reaction proceed faster and shift the equilibrium towards the products or reactants, depending on the enthalpy change and the nature of the reaction.