An amount charcoal is burned to produce 4.2x106 cal energy. What mass of water can be heated from 25.0 ºC to 150.0 ºC with this amount of energy? The specific heat of water is 1.000 cal/g ºC.

b. is the answer hoped i        

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