Granite is a type of igneous rock. What determines the size of the crystals that form in a sample of granite? A. how large the sample is B. how quickly the rock cooled C. how many times those minerals have been in granite before D. how many impurities are in the granite

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

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