Answer:
pH = 4.2
Step-by-step explanation:
∴ C CO2 = 409.15 mg/L * ( g/1000mg ) * ( mol CO2/44.01g ) = 9.296 E-3 mol/L
∴ Ka = 4.3 E-7 = [H3O+] * [HCO3-] / [H2CO3]
mass balanace:
⇒ C H2CO3 = C CO2 = 9.296 E-3 = [H2CO3] + [HCO3-]
⇒ [H2CO3] = 9.296 E-3 - [HCO3-]
charge balance:
⇒ [H3O+] = [HCO3-]
⇒ 4.3 E-7 = [H3O+]² / ( 9.296 E-3 - [H3O+] )
⇒ [H3O+]² + 4.3 E-7 [H3O+] - 3.997 E-9 = 0
⇒ [H3O+] = 6.300 E-5 M
⇒ pH = - Log [H3O+]
⇒ pH = - Log ( 6.3 E-5 )
⇒ pH = 4.2