2. Periodic Table Layout. The periodic table is organized in horizontal rows and also in vertical
columns. Why do you think both rows and columns were used? *
(1 Point)

Explanation:

Columns and rows used in the periodic classification of elements shows trends in the properties of elements.

The periodic columns are called groups and they denote vertical arrangement of elements.

The horizontal rows are the periods.

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