H₂S from cigarette smoke was collected by bubbling smoke through aqueous NaOH and measured with a sulfide ion-selective electrode. Standard additions of volume V_S containing Na2S at concentration +c_S = 1.78 mM were then made to V₀ = 25.0 mL of unknown and the electrode response, E, was measured.

From a separate calibration curve, it was found that β = 0.985 in Equation 14-14. Using T =298.15 K and n = -2 (the charge of S^2-), prepare a standard addition graph with Equation 14-15 and find the concentration of sulfide in the unknown.

Vs (mL) E (V) Vs (mL) E (V) 0.046 5 3.00 0.030 0 1.00 0.040 7 4.00 0.026 5 2.00 0.034 4