For a concentration technique, stotal is given as 19.31 ± 0.035, smb is 0.22 ± 0.008, and ka is 0.154 ± 0.007 ppm–1, where stotal is the signal, ka is the method’s sensitivity for the analyte and smb is the signal from the method blank. if we want the overall percent uncertainty to be 2.6%, which statement is false below?
group of answer choices:
a. improving the signal’s uncertainty will improve the overall uncertainty
b. uncertainty in the method’s sensitivity dominates the overall uncertainty
c. we must improve the uncertainty in ka to ±0.004 ppm–1
d. none of the above

the answer is a for sure mark brainliest i had got this right on usatestprep

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