Question

The mass of the erlenmeyer flask alone is 88.000 grams. calculate the mass of the zinc and hcl after the addition of 25 grams of zinc to an open flask containing 15 ml hcl.

Answer 1

If concentration of HCl is 1 mol/dm³ :
m(erlenmeyer flask) = 88,00 g.
m(Zn) = 25,0 g.
V(HCl) = 15 ml = 15 cm³ = 0,015 dm³.
Chemical reaction: Zn + 2HCl → ZnCl₂ + H₂.
n(HCl) = c(HCl) · V(HCl).
n(HCl) = 1 mol/dm³ · 0,015 dm³ = 0,015 dm³.
n(Zn) = 25 g ÷ 65,4 g/mol = 0,38 mol.
n(H₂) = 0,015 mol ÷ 2 = 0,0075 mol.
m(H₂) = 0,0075 mol · 2g/mol =  0,015 g.