Which of the following is a single replacement reaction? a. cao + h2o yields ca(oh)2 b. mg + 2hno3yields mg(no3)2 + h2 c. naoh + hcl yields h2o + nacl d. ch4 + 2o2yields co2 + 2h2o

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