How do you predict the correct formula for the combination reaction between a nonmetal and a group a metal?

Refer to the Periodic Table.

Explanation:

To predict the correct formula for the combination reaction between a nonmetal and a metal group, you can simply refer to the Periodic Table and check what formula does it have for any particular element.

The Periodic Table has both the metal and non-metal group with their atomic masses and other characteristics. Looks for the formula of each element in the compound and add the number of molecules according to the chemical equation.

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer

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