The fuel tank of an airplane has a device that measures the fuel's temperature. Before the airplane
took off, the temperature of the fuel was 27°C. After the airplane had been flying for one hour, the
temperature of the fuel had decreased to 3°C. Which of the following must have happened to the
molecules of the fuel?

the maximum mass of nh3 is nh3 in grams

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