Calculate the formula mass of magnesium perchlorate, Mg(CIO4)2, in atomic mass units (amu or u).

The formula mass of Magnesium perchlorate, Mg(CIO₄)₂ : 223 g/mol

An atomic mass unit ( amu or "u")  is a relative atomic mass of 1/12 the mass of an atom of carbon-12.  

The molar mass(molecular mass-formula mass) of a compound is the sum of the relative atomic mass (Ar) of the constituent elements of the compound

Can be formulated :  

M AxBy = (x.Ar A + y. Ar B)  

Compound Mg(CIO₄)₂ :

M = Ar Mg + 2. Ar Cl + 8. Ar O

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