Jennifer mixes substances during a lab experiment. She observes the four effects listed below. Which of these effects indicated that a chemical reaction has taken place? NEED HELP ASAP!!! a. A clear, lemon-scented liquid continues to smell like lemon when it is mixed with water.
b. A piece of shiny metal begins to bubble when placed in a clear liquid.
c. A pink powdered substance turns water pink when they are mixed together.
d. A white solid disappears when mixed with water.

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