Consider the energy transfers and transformations that occur when a person rides a bicycle. Describe this process by selecting the correct options from the drop-down menus. Chemical energy is transformed into energy in the person’s muscles. Kinetic energy is from the person’s legs to the pedals. Kinetic energy is thermal energy due to friction when the wheels get warm.

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