15.23?

[Adriana Rangel 1A]

In part C, why isn't [A]t going to be equal to .034? Why do we have to multiply it by two and then subtract that from the concentration of [A] 0 ?

[Carlos Gonzales 1H]

0.034 is the concentration in terms of B. You have the initial concentration in terms of A so you must convert [B] to [A] using the stoichiometric coefficients.

[Sean Monji 2B]

Just to clarify, in a reaction where 2A -> B + C, if B is increasing by 0.034 (assuming B initial = 0), then A must decrease by 0.034 * 2 since the reaction requires 2 A to be converted into B. As A initial = .134 and the change in A is -0.034 * 2, A at time t is .134 - 2 * 0.034.
Of course, C can be ignored.
Hope that makes sense

[April P 1C]

On chegg part of the solution is written :

[A] = [A]* - ([B]/2)
[A] = (0.153)- 2(0.034) = 0.085

Why is the first part written as ([B]/2) ?