Download Stoichiometry_files/5-Limiting React Lab 1.cwk (WP).

Chemistry
LIMITING REACTANT
Lab
Name_____________________________ Period______
PURPOSE
To determine the stoichiometric relationship of two reactants and to demonstrate the concept of a
limiting reactant.
EQUIPMENT
Electric Balance
Glass/Plastic Funnel
Ring Stand Set Up
100 ml Beaker
SUPPLIES
Safety goggles
Gloves
Apron
CHEMICALS
20 ml HCl
1 small chunk of zinc metal (mossy)
PRE-LAB CALCULATIONS
1.) Find the mass of the 20 ml of HCl
Mass of empty 100 ml beaker
___________ g
Mass of beaker + 20 ml HCL
___________ g (if you get an “error” message on the
scale use the other scale)
Mass of HCl
___________ g
2.) Weigh the chunk of zinc metal
__________ g
3.) Fill in the blanks:
Zn + 2 HCl -----> ZnCl2 + H2
In the above equation, _________ g of Zinc metal is added to _________ g of
hydrochloric acid (HCl). In the reaction, hydrogen gas (H2) is released while zinc chloride is
produced.
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4.) Calculate the following from the above knowns:
Zn + 2 HCl -----> ZnCl2 + H2
a.) What is the limiting reactant in this reaction?
b.) What is the reactant in excess in this reaction?
c.) According to your calculations how much ZnCl2 can be made in this reaction?
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PROCEDURE
1. Pour 20 ml of HCl into your 100 ml beaker.
2.) Obtain the masses of the following:
Initial mass of Zinc metal
___________________g
Mass of filter paper
___________________g
Mass of HCl
___________________g
3.) Drop the zinc metal into the beaker of HCl (be careful of the splash & wash immediately if you get
any on you).
4.) Describe what happens when you drop the Zinc into the HCl?
5.) What is causing this to happen? (HINT: look at your equation)
6.) Feel the bottom of the beaker. What do you feel?
7.) How will you know when the reaction is over?
8.) When the reaction appears over you need to check to see if there is anymore HCl in the beaker. Use
a pH strip to test for acids. What did you find out? What does that tell you about which reactant
is the limiting reactant?
8.) When the reaction is over you will need to get the weight of the beaker and liquid.
Mass of beaker (after reaction)
___________________g
8.) When the reaction is over pour the contents of the beaker through the DRY filter paper & funnel.
(You will need to use another beaker to catch the liquid)
9.) When the contents are filtered, spread your filter paper over a paper towel, LABEL it with your
name and put it in the cabinets on the back wall.
10.) We will continue tomorrow when the filter paper is dry.
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DATA COLLECTION (Day 2)
1.) Weigh the dry filter paper:
__________ g
2.) Calculate the amount of ZnCl2 that is on the filter paper.
Dry Filter Paper From Day 2 - Original Filter Paper From Day 1
__________ g ZnCl2
INTERPRETATION
I. How does the amount of ZnCl2 that you calculated would be produced compare to the actual amount
that you found?
ZnCl2 calculated in PRE-LAB ___________ g
ZnCl2 produced in the LAB
___________ g
2.) Calculate the PERCENT ERROR in the two figures.
% ERROR =
(ZnCl2 calculated in PRE-LAB - ZnCl2 produced in the LAB)
ZnCl2 calculated in PRE-LAB
x 100
% ERROR =___________
A positive (+) % ERROR means that the produced mass is ____________ than the calculated mass.
A negative (-) % ERROR means that the produced mass is ____________ than the calculated mass.
3.) Did your lab show the correct limiting reactant, as you predicted in your calculations?
4.) Did your lab show the correct product in excess, as you predicted in your calculations?
5.) How close was your predicted mass of ZnCl2 and the actual mass of ZnCl2?
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