Information
Urban climate
class
air pollutants
name
date
Air contaminants from exhaust gases of motor vehicles
Exhaust gases are hazardous to your health and should not be inhaled!
Use a fume hood or work outside.
Chemicals:
TAKE CARE: Some chemicals used in the experiment are harmful.
Experiment carefully and use safety equipment!
concentrated ammonia (25%) [C, N; R: 34-50; S: 26-36/37/39-45-61]
solution of silver nitrate, AgNO3 (aq), (ca. 2%)
aqueous solution of calcium hydroxide, CaOH (aq)
N(1-naphthyl)ethylenediamine dihydrochloride [Xi; R: 36/38; S: 22]
sulfanilic acid [Xi; R: 36/38-43; S: 2-24-37]
acetic acid [C; R: 10-35; S: 1/2-23-26-45]
distilled water
Preparation of the Saltzmann-solution
This solution measures nitrous acid. This is formed when nitrogen oxides react with water.
Dissolve:
5g sulfanilic acid
0.050g N, (1-naphthyl)-ethylenediamine dihydrochloride
50ml acetic acid
in 800ml distilled water.
Make the solution up to one litre with distilled water. In the absence of light and air the solution can be
stored for months.
Basic materials needed for each group (you may also need other materials, it depends on how you plan
your experiment):
3
2
2
gas-washing bottles
or alternatively: test tubes with offset extension, gas-entry tube (bent glass tube) and suitable
plug
cuvettes or small, clean test tubes of the same shape
glass syringe (with clip)
retort stands, clamps, sockets
flexible tube pieces (as connecting pieces)
bag for sample collection (see below)
flexible tube fitting the gas-entry-tube and the glass stopcock
© 2004 ESPERE-ENC / Seesing, Tausch, Universität-Duisburg-Essen; Duisburg
Worksheet
No.____a
Urban climate
class
air pollutants
name
date
Air contaminants from exhaust gases of motor vehicles
1. Preparation and sample collection of exhaust gas in freezer bags
You will need sample collection bags to collect and transport your exhaust gas samples. We recommend
using commercial freezer bags (without fasteners). Before using them as collection bags they have to be
modified as follows:
Materials needed for each bag:
1
freezer bag (or a thick airtight and gas-impermeable plastic bag) with a volume of 3 to 10 liters
1
tube (glass, plastic or metal) length: 15-30 cm, diameter: 25- 50 mm
broad plastic tape
1
rubber stopper (for the connection of the glass stopcock with the glass tube, see pictures 1-4)
1
glass stopcock (or glass tube with rubber hose and clamp)
picture 2
picture 1
picture 3
picture 4
Place the glass tube in the middle of the open side of the bag. Make sure it reaches well in to the bag.
Seal the bag by applying tape to the open edges of the bag then wrap these sealed edges around the
glass tube and tape again tightly (see pictures 1-4 above).
Taking the sample:
Avoid inhaling the exhaust gases and burning yourself on the exhaust pipe!
You can usually take the sample by removing the stopper, wrapping the end of
the glass tube with a piece of cloth, removing all air inside the bag and placing
the glass tube tightly at the end of the exhaust pipe (see picture no. 5). Flush
the bag once with the exhaust gas before taking the actual sample. As soon as
picture 5
the bag is filled with gas for a second time attach the closed stopper to the
glass tube (see picture no. 4). Take samples from vehicles with different engine types, as soon as the
engine is switched on and once it has reached its operating temperature.
T1
Make a sample collection bag for each sample you plan to take.
T2
Take your samples, number each of them and find out which engine type you have taken your
exhaust gas sample from. Analyse the samples the same day you collect them.
Table 1
petrol
engine
4 stroke
without catalytic converter
cold engine
engine at operating
temperature
sample no.1
sample no.2
Yamaha XZ550
Yamaha XZ550
cold engine
with catalytic converter
engine at operating temperature
sample no.3
Audi 100
2 stroke
diesel
engine
4 stroke
sample no.4
VW Golf II 1.6l
sample no.5
VW Golf II 1.6l
2 stroke
© 2004 ESPERE-ENC / Seesing, Tausch, Universität-Duisburg-Essen; Duisburg
Worksheet
No.____b
Urban climate
class
air pollutants
name
date
Air contaminants from exhaust gases of motor vehicles
2. Qualitative analysis of exhaust gas (CO, CO 2 und NOx)
T3
Read the information below and complete the missing reaction schemes!
1. Identification of carbon monoxide with an ammoniac solution of silver nitrate:
Properties of carbon monoxide: solubility in water 0.23 g L-1 (20 °C), boiling point: -191 °C, reducing agent,
highly toxic in concentrations w>5%
Reaction scheme for this identification:
2 [Ag (NH3)2]+(aq) + 2 H2O(l) + CO(aq)
2 Ag(s) + 4 NH4+(aq) + CO32-(aq)
2. Identification of carbon dioxide with lime water (aqueous solution of calcium hydroxide):
Properties of carbon dioxide: solubility in water 1.78 g L-1 (20 °C), sublimes: -79 °C
Reaction scheme for this identification:
Ca(OH)2 (aq) + CO2 (aq)
CaCO3 (s) + H2O(l)
3. Identification of nitrogen oxides with Saltzmann solution:
Properties of nitrogen dioxide: reacts with water yielding HNO 2 and HNO3, boiling point: 21 °C, vapour
pressure: 1013 hPa at 20 °C, highly toxic in concentrations w>1%
Reaction scheme for this identification:
Exhaust gases contain substances that are hazardous to your health:
Carrying out the experiments in a fume hood or work outside !
T4
Plan an experimental set-up and a procedure which meets the following criteria:
1. Each exhaust gas sample should be simultanuously tested for carbon monoxide, carbon dioxide
and nitrogen oxides.
2. The identification should be arranged in the order in which they do not falsify of interfere with
each other. (Take into consideration the different solubilities, reactivities with water and
reaction products.)
3. A semi-quanitative differentiation of the concentration of the pollutants in the different exhaust
gas samples should be made by controlling the volume of the tested exhaust gases.
© 2004 ESPERE-ENC / Seesing, Tausch, Universität-Duisburg-Essen; Duisburg
Order of identification:
1. Identification of nitrite with ~ 2-3 mL Salztmann solution: nitrogen dioxide reacts with water and
is easily washed away from the exhaust gases.
2. Identification of carbon dioxide with ~2-3 mL aqueous solution of calcium hydroxide: the
solubility of carbon dioxide is also relatively high, but the amount of carbon dioxide is high
enough to do this identification second.
3. Identification of carbon monoxide with a mixed ammonia (~ 0.5 mL concentrated ammonia
solution) and silver nitrate solution (~2 mL of a 2% solution): The solubility of carbon monoxide
in water is relatively poor. A product of this identification is carbon dioxide. Therefore the
identification of carbon dioxide has to be carried out before (see step 2).
The sensitivity of the proofs is enhanced because only a relatively small volume of the sample is
examined.
a: sample collection bag
b: Saltzmann- solution
c: aqueous solution of calcium hydroxide
d: ammoniacal solution of silver nitrate, AgNO3 (aq)
e: threeway valve for sucking in the combustion gases and for emptying the glass syringe
f: glass syringe for sucking in the combustion gases and measuring the gas volume
Man sauge etwa 200-600mL Abgas langsam durch die Apparatur. (der Nitritnachweis
© 2004 Seesing,
benötigt
etwasTausch,
Zeit.)Universität Duisburg-Essen, Duisburg
In our experiments, 400 mL of exhaust gas was used.
If you want to do more than one measurement in the same apparatus make sure you
thoroughly clean and dry section “b“.
The fact that the identifications do not interfere with each other can be proved by blowing
the pure pollutants through the apparatus.
T5
Analyse your exhaust gas samples and list your results in the table below.
sample no.
CO
CO2
NOx as NO
1
2
3
4
5
a lot
a little less
hardly detectable
a lot
less
a lot
a lot
a lot
a lot
a lot
a little less
a lot
little
a great amount
a great amount
A lot of carbon monoxide is emitted from cold engines. Catalytic converters
remove large amounts of carbon monoxide and nitrogen oxides from vehicle
exhaust gases. All engines emit large amounts of carbon dioxide into the air.
© 2004 ESPERE-ENC / Seesing, Tausch, Universität-Duisburg-Essen; Duisburg