Experimental measurements of rxn rates

VolumeChanges of a Gas

eudiometer

Volume (mL) 4.0 5.1 5.9 6.8 7.6 8.3

Time (s) 0 15 30 45 60 75

Zn(s) + 2HCl(aq) → H2(g) + ZnCl2(aq)

 

 

Rate in mL/s H2

Rate in mol/min for H2

Rate in g/h for HCl

15 30 45 60 75 (time sec)

Volume (mL)

87654321

0

Rise:8.3-4 = 4.3

Run: 75-0 = 75

Slope=Rise/Run=4.3/75=0.057 mL/s

Changes in Pressure

(constant volume or sealed container)

• if more moles of gas (coefficient) in products, pressure will go up

Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)

____m.o.g. ____ m.o.g.

• If more MOG in reactants, pressure will __________________________

•  rate = ∆ pressure (constant volume)

∆ time 

If equal MOG, pressure will not change: NO2(g) + CO(g) CO2(g) + NO(g) 2 m.o.g. 2 m.o.g.

Mass of an open container {Changes in Mass} 

Mass (g) 82.07 81.84 81.71 81.66 81.64 81.63

Time (s) 0 15 30 45 60 75

CaCO3(s) + 2HCl(aq) → CO2(g) + CaCl2(aq) + H2O(l)

CaCO3(s) + 2HCl(aq) → CO2(g) + CaCl2(aq) + H2O(l)

1. Calculate the rate in units of grams/s for CO2

2. Calculate the rate in grams/h for CaCO3

Hebden p 5 exercises: 7-9 + Page 11 questions