given a reaction and the kcals given off in a rxn, how many grams of HCl were used?

Question

4HCl(g) + O(g) <=> 2H20(g) + 2Cl(g)

If only 6.75 kcals were given off in this reaction, how many grams of HCl were used in the reaction?

let me know how to do this, please! thanks.

Answer 1

You need to look up the delta H per mole for this reaction. Each delta H per mole is related to 4 moles of HCl. Based on the actual heat given off, you can calculate how many moles of HCl were used and then easily convert that to grams by multiplying by the molecular mass.