posted by sai .
0.042g of Magnesium was reacted with excess HCl at S.T.P.
A. Write the equation for the reaction
B. How many moles of Mg were used?
C. What volume of Hydrogen is produced in this reaction?_
Mg + 2HCl = MgCl2 + H2
.042g Mg = .00173 mole Mg
so, you get .00173 mol H2
it will occupy .00173*22.4 = .0387L, or 38.7mL