What is the oxidation state of Cl in HCIO2?
A. +3
B. -1
O C. -3
D. +4

Bro,it's  number A

+3

Explanation:

The oxidation number for chlorine in HClO2 is plus three because oxygen is more electronegative than chlorine and is assigned negative two for each oxygen and hydrogen had a plus one. The sum of oxidation numbers is equal to the charge on the molecule, in this case zero.

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