State the number of significant 2804, 2.84, 5.029, 0.0030681

Explanation:

Significant numbers generally helps in measurement to express the accuracy of recorded experimental figures.

In order to solve the problem, there are rules that guides the identification of significant figures.

Some of these rules are:

According to these rules, we can state the number of significant figures in the values:

2804      4 significant figures

2.84         3 significant figures

5.029       4 significant figures

0.0030681   5 significant figures

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons

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