Which of the following is an example of a chemical change? O A. A sugar cube being crushed by a spoon
O B. A sugar cube dissolving in water as the water is stirred
O C. Sugar mixing with red food coloring and forming a red solid
O D. Sugar breaking down into water and carbon when it is heated

since electrons are negative the answer is neagtaive

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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

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