Electronic configuration of first 20 elements

Explanation:

Electronic Configuration of First 30 Elements with Atomic Numbers

Atomic NumberName of the ElementElectronic Configuration

18Argon (Ar)[Ne] 3s2 3p6

19Potassium (K)[Ar] 4s1

20Calcium (Ca)[Ar] 4s2

21Scandium (Sc)[Ar] 3d1 4s2

26 more rows

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