chemistry
posted by preshi .
Zinc metal reacts with HCL similarly to magnesium: Zn(s) + 2HCL(aq) = ZnCl2(aq) + H2(g). the H2 gas produced was collected over water at 25 degrees Celsius and had a volume of 7.80L at 0.980 atm. How many grams of Zn were consumed in the reaction? (Vapor pressure of water at 25C = 23.8mmHg)
please show me how to get the answer

Zn+ 2HCl ==> H2 + ZnCl2
Use PV = nRT and solve for n = number of mols H2.
Substitute [0.980 atm  (23.8/760)] for P.
Don't forget T must be in kelvin.
After you have obtained n, convert from mols H2 to mols Zn using the coefficients in the balanced equation. The g Zn = mols Zn x molar mass Zn.