Step 5: Measuring the Volume of Air Near 20°C (Room Temperature)
Use tongs to put the beaker (with tube and
thermometer) on the hot plate.
600
500
400
600 ml
00
200
100
Temperature of gas: 40
7 °C
Height of the column of gas:
16.7
cm RETRY

I failed it but I got the answers:

Step 5:
Temp of gas: 21c
Height of column gas: 6.2cm
Temp of gas: 294K
Volume of gas:0.78cm

the answer is a and have a great day

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