Consider the reaction: h2(g) + cl2(g) --> 2hcl(g)

using standard absolute entropies at 298k, calculate the entropy change for the system when 2.28 moles of h2(g)react at standard conditions.

Answer : The entropy change of reaction for 2.28 moles of reacts at standard condition is 45.8 J/K

Explanation :

The given balanced reaction is,

The expression used for entropy change of reaction is:

where,

= entropy change of reaction = ?

n = number of moles

= standard entropy of formation

= 130.684 J/mol.K

= 223.066 J/mol.K

= 186.908 J/mol.K

Now put all the given values in this expression, we get:

Now we have to calculate the entropy change of reaction for 2.28 moles of reacts at standard condition.

From the reaction we conclude that,

As, 1 moles of has entropy change = 20.066 J/K

So, 2.28 moles of has entropy change =

Therefore, the entropy change of reaction for 2.28 moles of reacts at standard condition is 45.8 J/K

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