(a)(i) The initial concentration of the chemical is given by \( C(0) = 30(0.75)^0 \). Since any number raised to the power of 0 equals 1, this simplifies to: \[ C(0) = 30 \times 1 = 30 \, \text{mg/L} \] Therefore, the initial concentration of the chemical in the bloodstream is \( 30 \, \text{mg/L} \). Answer: \( 30 \, \text{mg/L} \). [1]

(ii) The percentage of the chemical that leaves the blood each hour is calculated by: \[ 100 \times (1 – 0.75) = 25\% \] This means that 25% of the chemical is removed from the blood each hour, and the remaining 75% stays in the bloodstream. Thus, the percentage of chemical that remains is 75% each hour, while 25% leaves the bloodstream. Answer: \( 25\% \). [2]

(b) The amount of the chemical remaining in the blood after 8 hours is given by: \[ C(8) = 30(0.75)^8 \] First, calculate \( (0.75)^8 \), which is approximately \( 0.100112 \). This represents the proportion of the chemical still in the bloodstream after 8 hours. Next, multiply this value by the initial concentration of 30 mg/L to find the amount of the chemical remaining in the blood after 8 hours: \[ 30 \times 0.100112 \approx 3.00 \, \text{mg/L} \] This shows that after 8 hours, only about 3.00 mg/L of the chemical remains in the blood. Answer: \( 3.00 \, \text{mg/L} \). [2]