A first-order reaction is 50 percent complete in 30 minutes. Calculate...
To solve this problem, we can use the first-order reaction equation:
ln(No/N) = kt
Where:
No = initial concentration of the reactant
N = concentration of the reactant at a given time
k = rate constant
t = time
We are given that the reaction is 50 percent complete in 30 minutes. This means that N/No = 0.5. Substituting this into the equation, we get:
ln(0.5) = k * 30
Solving for k, we find:
k = ln(0.5)/30
Now we need to find the time taken for completion of 87.5 percent of the reaction. This means that N/No = 0.125. Substituting this into the equation and solving for t, we get:
ln(0.125) = (ln(0.5)/30) * t
Simplifying this equation, we find:
ln(0.125) = ln(0.5)/30 * t
Taking the exponential of both sides, we get:
0.125 = e^(ln(0.5)/30 * t)
Simplifying further, we find:
0.125 = (0.5)^(1/30 * t)
Taking the logarithm of both sides, we get:
log(0.125) = log((0.5)^(1/30 * t))
Using the logarithmic identity log(a^b) = b * log(a), we can rewrite the equation as:
log(0.125) = (1/30 * t) * log(0.5)
Simplifying further, we find:
log(0.125) = (1/30 * t) * (-0.301)
Solving for t, we find:
t = (log(0.125) / (-0.301)) * 30
Calculating this expression, we find that t is approximately 89.9 minutes. Thus, the time taken for completion of 87.5 percent of the reaction is approximately 90 minutes, which corresponds to option c.
A first-order reaction is 50 percent complete in 30 minutes. Calculate...
Reaction is 50 percent complete in 30 minutes. Hence, t1/2 = 30 minutes
75 percent of the reaction is completed in two half-lives. Hence, t = 2 × 30 = 60 minutes
87.5 percent of the reaction is completed in three half-lives. Hence, t = 3 × 30 = 90 minutes.