Measuring the mass of a reactant in excess Name:_____________
Reaction: 2HCl + Zn  ZnCl2 + H2
Procedure:
1.Weigh an empty test tube.
2. Put about 2 grams of zinc in it and weigh it.
Data:
3. Pour in about 5 mls of HCl acid and weigh it.
Mass of empty test tube:
Subtract to calculate #1 and #2
Mass of test tube + zinc:
#1 Mass of zinc=
Mass of test tube + zinc + HCl acid:
#2 Volume of HCl in liters=
(Hint: 1gram = 0.001 liters)
Calculations and questions:
(a) Calculate the moles of Zinc
from #1: (Zn = 65.4 g/mol)
(b) Calculate the moles of HCl
from #2. (Conc. 4.0 mol/liter)
(c) Calculate the moles of zinc in
excess. Use your a and b
calculations and the reaction
equation:
2HCl + Zn  ZnCl2 + H2
(d) Convert the moles of zinc to
grams. (Zn = 65.4 g/mol)
(This is the Theoretical mass of zinc)
Let the reaction go on for about 10 minutes and then pour out the liquid being careful not
to lose the excess zinc. Remove the lump of zinc and dry it with paper towel and weigh it.
Actual Mass of excess zinc:
(e) What is the experimental error:
Theoretical mass of zinc from(d) - actual mass of zinc x 100 =
Theoretical mass of zinc from(d)
(f) List three sources of error?