Keq problem

[Steve19]

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what is the closest to the value of the equilibrium constant Keq. for the following equilibrium ?
HCl + H2O <----> H3O+ + Cl -
a) 10^-5
b) 10^-3
c)1
d)10^3
e)10^5

it says the answer is d or 10^3....how can u calculate the Keq ??

 

[SanDiegoSOD]

Where A + B ---> C + D, Keq is [C][D]/[A]

 

[tom_servo_dds]

what is the closest to the value of the equilibrium constant Keq. for the following equilibrium ?
HCl + H2O <----> H3O+ + Cl -
a) 10^-5
b) 10^-3
c)1
d)10^3
e)10^5

it says the answer is d or 10^3....how can u calculate the Keq ??

Just my .02 - you should be able to get to the point where you can look at a reaction and see which direction it is most likely going to go. The trick is knowing that reactions proceed in the direction that produce the weakest acid. So in this case HCL (acting as the base on the left side of the reaction) is a stronger acid than H30+ on the right (a weaker acid). Also, you should know the list of strong acids that almost completely dissociate in water, HCl being one of them (here's some others: http://en.wikipedia.org/wiki/Strong_acid#Some_Common_Strong_Acids_.28As_Ionisers.29). Knowing this and the previous post to mine as far as the deffinition of what Keq is, you should be able to eliminate the first three choices right off the bat. As far as the next two, I don't see how you could know between them. Anyone else have some thoughts on this?

 

[lifeisgood]

Just my .02 - you should be able to get to the point where you can look at a reaction and see which direction it is most likely going to go. The trick is knowing that reactions proceed in the direction that produce the weakest acid. So in this case HCL (acting as the base on the left side of the reaction) is a stronger acid than H30+ on the right (a weaker acid). Also, you should know the list of strong acids that almost completely dissociate in water, HCl being one of them (here's some others: http://en.wikipedia.org/wiki/Strong_acid#Some_Common_Strong_Acids_.28As_Ionisers.29). Knowing this and the previous post to mine as far as the deffinition of what Keq is, you should be able to eliminate the first three choices right off the bat. As far as the next two, I don't see how you could know between them. Anyone else have some thoughts on this?

I totally agree with you. The first 3 are obviously wrong and you would need more info to distinguish between the last 2 answers.