Rainwater collected in akron contains pb, cu and zn at 8.5, 5.0 and 7.5 ug/l. determine these concentrations in units of mol/l (or nmol/l). b) this same rainwater contains 0.8 mg/l ca and 1.2 mg/l mg. determine the hardness of this water in units of mg/l as caco3. hardness is the sum of the concentrations of multivalent cations in the water, which in this case include ca (as ca2+) and mg (as mg2+). hardness is expressed in "equivalent" units or "caco3" units.

answer: i dont know the answer but this might

explanation:

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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