27.0 g piece of aluminum (which has a molar heat capacity of 24.03 J/oC mol) is heated to 94.2 oC and dropped into a coffee cup calorimeter containing water initially at 19.9 oC. The final temperature of the water and aluminum mixture is 23.3 oC. Calculate the mass of water in the calorimeter. The specific heat of water is 4.184 J/g oC.

1 a

2 d

3 a

4 c

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

i think tornado but not 100%