The periodicity of the properties of elements is chiefly due to the

i) numbers of electrons in the atoms of the elements

ii) distribution of electrons in the atoms of the elements

iii) numbers of neutrons in the atoms of the elements

a) i only

b) i and iii only

c) all of these

d) ii only

e) iii only

f) ii and iii only

g) none of these

h) i and ii only

option A.

Explanation:

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