Wash an
evaporating dish
soap and water.
Rinse & Dry
0
Evaporating
dish
Put evaporating dish on a plate and
heat it ON HIGH for 5-10 minutes
to remove any trace of moisture.
(sample has to be dry)
On the same hot plate, heat a 400mL
Beaker lled with about 250 mL of
tap water. (This will be served as a
“hot bath”)
Crucible
tongs
Cool the dish in room temperature
Add about 0.3g of sodium
carbonate (Na2Co3) to the
evaporating dish and reweigh.
Weigh the cool evaporated dish and
Record its value ⭐
record its mass ⭐
Obtain about 5mL of 3.0 M
hydrochloric acid in a 10mL
graduated cylinder
Moisten the sodium carbonate with a
small amount of distilled water and
add 4 drops of methyl red indicator.
0
glass
Watch
Add the 3.0M hydrochloric acid DROP
WISE down the spout of the
evaporating dish using a medicine
dropper and WITHOUT REMOVING the
watch glass until the solution is a faint
pink. (stir the evaporating dish while
putting the HCl)
DO NOT USE
EXCESS AMOUNT
OF WATER. it will
have to be boiled off.
p
Place the evaporating dish on top of the
hot bath to HEAT THE SOLUTION.
Medicine
dropper
Remove the watch glass. Rinse
any solids that may have been
collected on the watch glass
into the evaporating dish with
a small quantity of water.
As the solution is
heating, it may turn
yellow, if this
occurs add more
HCl until the colour
pink returns
Continue heating the solution gently. As
the mixture in the evaporating dish
becomes more concentrated, it will tend
to “bump” and spatter if the heating rate
is excessive (resulting in a loss of
product).
IF the contents of the evaporating dish
begin to spatter, return the evaporating
dish to the hot bath for ADDITIONAL
SLOW HEATING.
IF no spattering occurs, continue heating
the evaporating dish directly with LOW
HEAT for a few more minutes.
Weigh the cool evaporating dish and
its content.
When the residual solid (NaCl) is almost
dry, lower the heating of the hot plate
to a MINIMUM. Remove evaporating
dish from the steam bath, dry the
bottom of the dish and place it directly
on the hot plate.
Begin heating the evaporating dish
directly on the hot plate.
Remove the evaporating dish from the
hot plate and allow it to COOL to a
ROOM TEMPERATURE.
Use this time to start
calculations and solve
post-lab problems.
Reheat and reweigh until a constant
mass is obtained.
*CALCULATIONS TO BE DONE*
1. Mass of Sodium Carbonate used.
2. From the mass of sodium carbonate, determine the mass of sodium chloride (NaCl)
that SHOULD be produced in the reaction.
3. Using calculated THEORETICAL mass and the MEASURED mass of the NaCl,
calculate the percent yield* of the experiment.
*the percent ratio of the actual yield divided by the theoretical yield X 100%
PRE-LAB QUESTIONS:
1.If 10.0g Na2CO3 are treated with excess HCl, calculate the theoretical yield of NaCl
Nazcoz12HCl 2NaCl 1H2O
105.99g
1
CO2
58.44g
x O094m01
ANSWER Totalyield
of NaCl is
10.99g
b188m01 moi
x 10.99g
2. Calculate the volume of 3.0M HCl required to react completely with 10.0g Na2Co3
Nazcoz12HCl 2NaCl
0094m01 X
H2O CO2
ANSWER
Thevolume of HCl
required is 62.66mL
X O188m01
My
0.188M
3OM
0.06266Ld62.67mL
3. Is the mass of NaCl a ected by its temperature? (hot vs cold)
No thetemperature has no affect on the mass of Nacl unless it reaches its
freezing1boilingpoint
4. If the mass of the NaCl is measured while the evaporating dish is still hot, what a ect will this have
on the recording mass, in grams?
Thedensity of a hot evaporating dish is smallerthan a room temperature
dish it is
dish therefore if youweigh themassofNaCl on a hot evaporating
mostlikelyto be lighter than itsactualmats