Based on Reference Table J, which two reactants react spontaneously? A)Mg(s) + ZnCl₂(aq)
B)Cu(s) + FeSO₄(aq)
C)Pb(s) + ZnCl₂(aq)
D)Co(s) + NaCl(aq)

28528289 29823282 8298232 39858

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