When a student added 13gm of zinc to 50cm3 of HCl acid . Calculate :1) The number of moles of zinc added. 2) The mass of ZnCl2 formed. 3) The volume of H2 gas produced

Answer 1

1) moles of Zn added:

atomic wt zinc = 65.39

13 g x 1 mol/65.39 g = 0.1988 moles = 0.20 moles (2 sig. figs.)

2) mass of ZnCl2 formed:

balanced equation is Zn(s) + 2HCl(aq) ==> ZnCl₂(aq) + H₂(g)

0.20 mol Zn x 1 mol ZnCl₂/mol Zn x 136.4 g/mol ZnCl₂ = 27.3 g = 27 g ZnCl₂ (2 sig. figs.)

3) volume of H2 gas produced (assuming standard temperature and pressure, i.e. STP):

0.20 mol Zn x 1 mol H2/mol Zn x 22.4 L/mol = 4.48 liters = 4.5 liters H₂ (2 sig. figs.)