Using the following standard reduction potentials, Sn3+(aq) + 2e- → Sn2+(aq) E° = +0.15 V Pb2+(aq) + 2e- → Pb(s) E° = -0.13 V calculate the standard cell potential for the galvanic cell reaction given below, and determine whether or not this reaction is spontaneous under standard conditions. Pb2+(aq) + 2 Sn2+(aq) → 2 Sn3+(aq) + Pb(s)

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

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