magnesium react with hydrochloric acid,what is the volume of hydrogen produced at r.t.p when 0.12g of magnesium ribbon react?

Answer 1

balance the equation
Mg+2HCl>>>MgCl2 + H2

so one gets the same number of moles of H2 as moles one used of Mg.
MolesMg=.12/atomicmassMg

volumeH2=molesH2*RTPmolarvolume

Answer 2

Volume of hydrogen is 24dm3