Question

The peroxydisulfate ion (S₂O₈²⁻) reacts with the iodine ion in an aqueous solution via the reaction:

S₂O₈²⁻ (aq) + 2I- (aq) 2SO₄²⁻ (aq) + I₂ (aq).
An aqueous solution containing 0.050 M of S₂O₈²⁻ ion and 0.072 M of I- is prepared and the reaction progress is monitored. The data obtained are given in the table below:
Time (s) [I-] M
0.000 0.072
400.0 0.057
800.0 0.046
1200.0 0.037
1600.0 0.029
The average rate of disappearance of I- between 400.0 s and 800.0 s is ________ M/s
A) 3.6 x 10⁴
B) 1.4 x 10⁻⁵
C) 2.8 x 10⁻⁵
D) 5.8 x 10⁻⁵
E) 2.6 x 10⁻⁴

Answer 1

The average rate of disappearance of I- between 400.0 s and 800.0 s is -4.275 x 10^-5 M/s.

Step-by-step explanation:

The average rate of disappearance of I- between 400.0 s and 800.0 s can be calculated using the formula:

Average Rate = (Change in concentration of I-)/(Change in time)

Using the data given:

Change in concentration of I- = 0.029 M - 0.0461 M = -0.0171 M

Change in time = 800.0 s - 400.0 s = 400.0 s

Average Rate = (-0.0171 M)/(400.0 s) = -4.275 x 10^-5 M/s

Therefore, the average rate of disappearance of I- between 400.0 s and 800.0 s is -4.275 x 10^-5 M/s (or 4.275 x 10^-5 M/s in absolute value).