Question

How many moles of calcium carbonate are consumed in this reaction?

In a reaction between calcium carbonate and hydrochloric acid, if 225ml of 3.25 M HCl was used, find the moles of calcium carbonate consumed.

Answer 1

Well consider the stoichiometric equation:

`CaCO_3(s) + 2HCl(aq) rarr CaCl_2(aq) + CO_2(g)uarr +H_2O(l)`

Explanation:

Is it balanced with respect to mass and charge? It must be if we purport to represent chemical reality.

With respect to hydrochloric acid, we gots......

`3.25*mol*cancel(L^-1)xx225*mLxx10^-3*cancelL*cancel(mL^-1)=`

`0.731*mol`

And thus HALF an equivalent of calcium carbonate were consumed................i.e. `0.366*mol`, a mass of `0.366*molxx100.09*g*mol^-1`, approx. `37*g`.....

These sort of questions are VERY common at this level (A2 and 1st year university), because they test the student's grasp of stoichiometry and numeracy. An examiner could also ask the volume of carbon dioxide evolved under standard conditions.