Calculate the average atomic mass for an imaginary element "E" that has the following isotope abundances: 56.67 % E-102.658 amu
43.33% E-104.770 amu

Average atomic mass of E = 103.57 amu

Explanation:

Given data:

Average atomic mass of E = ?

Abundance of E-102.658 = 56.67%

Abundance of E-104.770 = 43.33%

Solution:

Average atomic mass of E = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)  / 100

Average atomic mass of E = (56.67×102.658)+(43.33×104.770) /100

Average atomic mass of E =  5817.63 + 4539.68 / 100

Average atomic mass of E = 10357.31 / 100

Average atomic mass of E = 103.57 amu.

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