Calculate the average rate of appearance of SO₂ across the following time intervals all centered on t = 175 min. Identify the best estimate for the instantaneous rate of appearance of SO₂ at t = 175 min and explain why.

(i) 50 to 300 min
(ii) 150 to 200 min
(iii) 100 to 250 min
(iv) 0 to 350 min

• A. (i) 5.2×10^–5 M/min
  (ii) 5.2×10^–5 M/min
  (iii) 5.3×10^–5 M/min
  (iv) 5.3×10^–5 M/min
  Rate (ii) is the best estimate because it is measured in the closest range of time.
• B. (i) 5.2×10^–5 M/min
  (ii) 5.2×10^–5 M/min
  (iii) 5.3×10^–5 M/min
  (iv) 5.3×10^–5 M/min
  Rate (iv) is the best estimate because it is measured in the largest range of time.
• C. (i) 5.4×10^–5 M/min
  (ii) 5.2×10^–5 M/min
  (iii) 5.6×10^–5 M/min
  (iv) 5.2×10^–5 M/min
  Rate (ii) is the best estimate because it is measured in the closest range of time.
• D. (i) 5.4×10^–5 M/min
  (ii) 5.2×10^–5 M/min
  (iii) 5.6×10^–5 M/min
  (iv) 5.2×10^–5 M/min
  Rate (iv) is the best estimate because it is measured in the largest range of time.

Answer: (A)