Look at the following chemical equation 4FeS + 702 - 2Fe2O3 + 4502

What is true about this chemical equation?

A. It is unbalanced because the sum of the coefficients of the reactants is greater than the sum of the coefficients of the products.

B. It is balanced because the mass of the reactants is equal to the
mass of the products.
C. It is balanced because the sum of the coefficients of the reactants is greater than the sum of the coefficients of the products.
D. It is unbalanced because the mass of the reactants is greater than
the mass of the products.

the answer is d.) potassium

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