This question is incomplete, the complete question is;
Consider this reaction:
2H₃PO₄(aq) → p₂o₅(aq) + 3H₂O(aq)
At a certain temperature it obeys this rate law.
rate = ( 46.65 M⁻¹.s⁻¹) [ H₃PO₄ ]²
Suppose a vessel contains H₃PO₄ at a concentration of 0.660 M .
Calculate how long it takes for the concentration of H₃PO₄ to decrease to 20.0% of its initial value .
You may assume no other reaction is important.
Round your answer to significant digits.
Answer:
time taken is 8.574 × 10⁻⁴ s
Step-by-step explanation:
Given that;
rate = k[ H₃PO₄ ]²
rate constant k = 46.65 M⁻¹.s⁻¹)
Initial concentration A₀ = 0.660 M { which will be 100%}
final concentration At = 20%
for the concentration of H₃PO₄ to decrease to 20.0% of its initial value = ?
we know that;
rate constant k = 1/t [ 1/At - 1/A₀ ]
we substitute
46.65 = 1/t [ 1/20 - 1/100 ]
46.65 = 1/t [ 0.04 ]
46.65 = 0.04/t
46.65t = 0.04
t = 0.04 / 46.65
t = 0.0008574 ≈ 8.574 × 10⁻⁴ s
Therefore, time taken is 8.574 × 10⁻⁴ s