Similar to alum, ferric chloride (FeCl3) is commonly used as a coagulant and flocculent in water treatment plants. When FeCl3 is placed in water, it forms Fe(OH)3 solids which helps remove small suspended particles. A 250,000 ppm concentration of FeCl3 is added to the raw water in the rapid mix basin at a flowrate of 5 GPM (gallons per minute). The flowrate of water to be treated is 20 MGD. Required:
What mass of Fe(OH)3) is generated each day (in kilograms/day)?

mass of Fe(OH)3) is generated each day (in kilograms/day)

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol