Second order reaction: [A] decreases 0.03 M in one hour, half-life calculation

[krootox217]

Homework Statement

The task is the following:

If the concentration of A decreases 0.03 M in one hour, then the concentration of B should to, which means, [ B] should be 0.05 M?

And if I try to calculate k, i get 14.87 l/(mol*h)

For second order reactions, t1/2 sould be 1/(k*[A]₀)

So I get 1.34 h as t1/2 for substance A, which somehow doesn't make sence, since more than 50% of the substance reacted in one hour. For B i get 9.29h, which doesn't make sense too. Can me someone tell my mistake?

Homework Equations

see above

The Attempt at a Solution

see above

 

[epenguin]

Homework Statement

The task is the following:

If the concentration of A decreases 0.03 M in one hour, then the concentration of B should to, which means, [ B] should be 0.05 M?

And if I try to calculate k, i get 14.87 l/(mol*h)

For second order reactions, t1/2 sould be 1/(k*[A]₀)

So I get 1.34 h as t1/2 for substance A, which somehow doesn't make sence, since more than 50% of the substance reacted in one hour. For B i get 9.29h, which doesn't make sense too. Can me someone tell my mistake?

Homework Equations

see above

The Attempt at a Solution

see above

If the concentration of A decreases 0.03 M in one hour, then the concentration of B should to, which means, [ B] should be 0.05 M? YES

I calculated the same rate constant as you.

Always good to check for reasonableness.

However I think that the simple relation of rate constant to half life only applies for the case of equal concentrations [A] = [ B]. ?

I am not sure there is any useful simple relation like that when these two are not equal. So I think you will have to work out each case using the full integrated rate equation, e.g. With [A]/[A₀] = ½ and [ B] = [ B₀] - [A₀]/2 etc.

 

[krootox217]

Ok, thanks for the answer, I found a way, where t1/2 for A yields 0.756h, which seems to make sence, at least for this reaction :)