Simply put, the time needed for #50%# of a reaction to be completed will represent that reaction's half-life. In your case, you know that your first-order reaction is #50%# completed after #30# minutes. This means that after #30# minutes, you will have . #A = 1/2 * A_0 -># half of the initial concentration remains after one half-life
How Long Is a Typical Half Marathon Training Schedule? As a first-timer, plan for 12 to 16 weeks of training from start to finish. This will allow you to build your endurance, strength, and confidence for the first 4-6 weeks, then complete the eight-week half marathon training plan to bring you right up to race day. The relationship between the decay constant λ and the half-life t1 / 2 is. λ = ln(2) t1 / 2 ≈ 0.693 t1 / 2. To see how the number of nuclei declines to half its original value in one half-life, let t = t1 / 2 in the exponential in the equation N = N0e − λt. This gives. N = N0e − λt = N0e − 0.693 = 0.500N0. "7.6 h" The thing to remember about first-order reactions is that their half-life is independent of the initial concentration of the reactant. In other words, it doesn't matter how much reactant you have, the half-life of the reaction, i.e. the time needed for half of the initial concentration of the reactant to be consumed, will be constant. Mathematically, you can express this as ["A"]_tThe #1 most important thing to remember is that you can and should always retreat to the stairwell you came up for cover. The #2 most important thing is that there's an infinite rocket crate fairly near the door to the stairs. Keeping those things in mind, you shouldn't have much trouble on the roof.