Misconceptions To Determine The Rate Of A Chemical Reaction
Chemical reactions proceeding until all the reactants are used is a common misconception. Chemical reactions actually behave differently. The general reaction equation is a A + b B → c C +d D in this equation A and B are the reactants forming the products C and D. However, unlike the common thought that the reaction ends when it runs out of A and B it actually does not. In most reactions C and D start to react to form A and B at a certain point as you can see in the equation c C + d D → a A + b B. These two reactions occur until the rate of reaction in both equations become equal (meaning the speed of the production of C and D in the first equation is equal to the speed of the production of A and B in the second equation) resulting in a
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chemical equilibrium. What is chemical equilibrium? Chemical Equilibrium can be defined as a state in which both reactants and products are present in concentrations, which have no further tendency to change with time. In addition, you might think that the reaction rate of forward and backward reactions at equilibrium would be zero; generally, this is not so, however, they will be equal. You might think okay that makes sense but when it reaches equilibrium does it stop? The answer to that question is no it does not stop when it reaches equilibrium A and B still react to form C and D, while C and D still react to form A and B. Due to the fact that the reactions occur at the same time and rate, the amount of each is constant. Since they are constant, are they all equal? Simply put no just because they are constant that does not mean they are necessarily equal.
To begin, an equation set that continues to occur after it reaches equilibrium can be said to be in a dynamic equilibrium state. It’s called this to emphasize that the reactions are still occurring. We can see if an equation is in dynamic equilibrium state if it is in the form of a A + b B →← c C +d D. We can see though constants will form.
In a situation where temperature is constant and the reaction rate is at equilibrium. Then the ratio of the two reactions (the forward and reverse) will become a constant. This constant is the reaction quotient, Q. Q has the form Q_C= [C] ^c [D] ^d / [A] ^a [B] ^b. The [ ] is meant show molar concentrations. If this was a gas phase reaction, gas pressures could be used and it would be Q_P. When can you write a reaction quotient? One can write a reactant quotient at any point during the reaction, but it is most meaningful is when it has reached equilibrium. At equilibrium, the reaction quotient becomes the equilibrium constant, K_(c )or K_p when gas pressure is being used.
Usually the equilibrium constant k is expressed as a simple number without units, since it is a ratio of concentrations or pressures.
The numerical value of the equilibrium constant gives an indication of the extent of the reaction, after reaching equilibrium. If K_(c )is large, then that means the numerator is much larger than the denominator and the reaction has produced a relatively large amount of products making the reaction lie far to the right. If K_(c )is small, then the numerator is much smaller than the denominator and not much product has been formed making the reaction lie far to the left. While thing can affect the constants the equilibrium system itself can be effected this was discovered by Le …show more content…
Chatelier.
Le Chatelier’s discovery became known as Le Chatelier’s Principle.
This principle can be used as a guild to help one work out what happens when you change the conditions of a reaction in dynamic equilibrium. Le Chatelier’s Principle states that if a dynamic equilibrium is disturbed by the changing of conditions, the position of equilibrium moves to counteract the change. By doing this the amount of reactants and products will be changed but the ratio between the two will remain the same. I get that if it is stressed it will shift to counteract the change but how can the chemical system at equilibrium be stressed? A chemical system at equilibrium can be stressed in a multitude of ways including a change in the concentrations, change in pressure if gases are being used and a change in temperature. Wait wouldn’t a catalyst have an effect on equilibrium and possible cause stress to the reaction? A catalyst while it seems like it would have an effect on equilibrium it does not since it affects both reverse and forward reactions equally. A catalyst only effect how quickly a reaction can reach equilibrium. Okay got it now that I know what can stress equilibrium how do I know how it counteract these conditions? Well it all depends on what conditions were changed. You see if the concentration of one of the reactants were increased then the equilibrium would react to remove the stress by increasing the amount of product and the position of equilibrium moves to the right. If the
concentration of one of the reactants would decrease equilibrium position, would move to the left and the inverse reaction would be used to try to replace the deficit of that reactant be creating more of it. As far as stressing equilibrium with pressure, it is only significant if gases are involved. When they are though the equilibrium will shift to the appropriate e side of the equation to fix the increase of reduction of pressure. Temperature is a little trickier than the others are because you must know whether heat is given out or absorbed during the reaction. If the temperature would increase, the position of equilibrium would move in such a way that would reduce the temperature again and vice a versa for decrease in temperature. Nevertheless, by doing this the concentrations and value of k might change.
To conclude, chemical equilibrium results when two exact opposite reactions occur at the same place and time with the same rate of reaction. In addition, systems that have reached chemical equilibrium do not stop. These equilibriums are considered dynamic and can be seen in the equation a A + b B →← c C +d D. Equilibrium also has constants, K_(c )or K_p when gas pressures are being used. K_(c )or K_p is the ratio of concentrations/ or pressures. We also know that thanks to Le Chatelier’s discovery that an equilibrium can be stressed by changes in pressure, concentration and temperature.
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chemical equilibrium. What is chemical equilibrium? Chemical Equilibrium can be defined as a state in which both reactants and products are present in concentrations, which have no further tendency to change with time. In addition, you might think that the reaction rate of forward and backward reactions at equilibrium would be zero; generally, this is not so, however, they will be equal. You might think okay that makes sense but when it reaches equilibrium does it stop? The answer to that question is no it does not stop when it reaches equilibrium A and B still react to form C and D, while C and D still react to form A and B. Due to the fact that the reactions occur at the same time and rate, the amount of each is constant. Since they are constant, are they all equal? Simply put no just because they are constant that does not mean they are necessarily equal.
To begin, an equation set that continues to occur after it reaches equilibrium can be said to be in a dynamic equilibrium state. It’s called this to emphasize that the reactions are still occurring. We can see if an equation is in dynamic equilibrium state if it is in the form of a A + b B →← c C +d D. We can see though constants will form.
In a situation where temperature is constant and the reaction rate is at equilibrium. Then the ratio of the two reactions (the forward and reverse) will become a constant. This constant is the reaction quotient, Q. Q has the form Q_C= [C] ^c [D] ^d / [A] ^a [B] ^b. The [ ] is meant show molar concentrations. If this was a gas phase reaction, gas pressures could be used and it would be Q_P. When can you write a reaction quotient? One can write a reactant quotient at any point during the reaction, but it is most meaningful is when it has reached equilibrium. At equilibrium, the reaction quotient becomes the equilibrium constant, K_(c )or K_p when gas pressure is being used.
Usually the equilibrium constant k is expressed as a simple number without units, since it is a ratio of concentrations or pressures.
The numerical value of the equilibrium constant gives an indication of the extent of the reaction, after reaching equilibrium. If K_(c )is large, then that means the numerator is much larger than the denominator and the reaction has produced a relatively large amount of products making the reaction lie far to the right. If K_(c )is small, then the numerator is much smaller than the denominator and not much product has been formed making the reaction lie far to the left. While thing can affect the constants the equilibrium system itself can be effected this was discovered by Le …show more content…
Chatelier.
Le Chatelier’s discovery became known as Le Chatelier’s Principle.
This principle can be used as a guild to help one work out what happens when you change the conditions of a reaction in dynamic equilibrium. Le Chatelier’s Principle states that if a dynamic equilibrium is disturbed by the changing of conditions, the position of equilibrium moves to counteract the change. By doing this the amount of reactants and products will be changed but the ratio between the two will remain the same. I get that if it is stressed it will shift to counteract the change but how can the chemical system at equilibrium be stressed? A chemical system at equilibrium can be stressed in a multitude of ways including a change in the concentrations, change in pressure if gases are being used and a change in temperature. Wait wouldn’t a catalyst have an effect on equilibrium and possible cause stress to the reaction? A catalyst while it seems like it would have an effect on equilibrium it does not since it affects both reverse and forward reactions equally. A catalyst only effect how quickly a reaction can reach equilibrium. Okay got it now that I know what can stress equilibrium how do I know how it counteract these conditions? Well it all depends on what conditions were changed. You see if the concentration of one of the reactants were increased then the equilibrium would react to remove the stress by increasing the amount of product and the position of equilibrium moves to the right. If the
concentration of one of the reactants would decrease equilibrium position, would move to the left and the inverse reaction would be used to try to replace the deficit of that reactant be creating more of it. As far as stressing equilibrium with pressure, it is only significant if gases are involved. When they are though the equilibrium will shift to the appropriate e side of the equation to fix the increase of reduction of pressure. Temperature is a little trickier than the others are because you must know whether heat is given out or absorbed during the reaction. If the temperature would increase, the position of equilibrium would move in such a way that would reduce the temperature again and vice a versa for decrease in temperature. Nevertheless, by doing this the concentrations and value of k might change.
To conclude, chemical equilibrium results when two exact opposite reactions occur at the same place and time with the same rate of reaction. In addition, systems that have reached chemical equilibrium do not stop. These equilibriums are considered dynamic and can be seen in the equation a A + b B →← c C +d D. Equilibrium also has constants, K_(c )or K_p when gas pressures are being used. K_(c )or K_p is the ratio of concentrations/ or pressures. We also know that thanks to Le Chatelier’s discovery that an equilibrium can be stressed by changes in pressure, concentration and temperature.
Word count 1132