One mechanism for storing solar energy for use at night or cloudy days is to use collected energy to melt salts. The stored energy would be retrieved by A. Converting molten salts to the gas phase.
B. Reacting molten salts with water to produce hydrogen gas.
C. Electrolyzing the molten salts.
D. Allowing salts to solidify to heat steam to drive a turbine.

i would say b

explanation:

but i think i would need more information than that

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