Kinetics 2 07.02.07
HQ Answers
1. 5.0 g x [ 60s ] = 2.0 g/min
150s 1 min
2. 45.0 g x 1 min/2.35g = 19.1 min
3. 7.50 min x 3.5 mL / min = 244 mL
4. Acceptable : a, c, e, f
5. 1.34 mol H2O/min x 1mol O/ 1mol H2O = 1.34 mol/min O
Note. 1.34 mol/min O ( 1 mol O2 ) = 0.670 mol/min O2
2 mol O
MEASURING REACTION RATE
The following data was obtained for the reaction:
NaHCO3 (s) + H+ (aq) à CO2(g) + H2O (l) + Na+ (aq)
Sodium Bicarbonate (Acid)
The mass of the reactants and products was measured.
The gas was allowed to escape.
Tests: CO2 does not support combustion
Or test for CO2 with limewater (Ca(OH)2)
CO2 + (Ca(OH)2) à CaCO3 (s) + H2O
Gas Clear white Precipitate (milky)
Calcium hydroxide Calcium carbonate
Time (s) |
Mass (g) |
0 |
150.00 |
10 |
149.94 |
20 |
149.88 |
30 |
149.82 |
|
|
Graph mass vs time
Questions
1. Why is the mass decreasing
2. What is the slope of the line on the graph?
3. What are the units of the…
a. Rise (Y axis)
b. Run (X axis)
c. Slope
4. What units are used for the rate of this reaction?
5. What relationship exists between the slope of the graph and the rate?
Answers:
1. It is an open system…. The CO2 is lost
6. – (slope) = reaction rate
What factors in a reaction could be measured as the reaction rate?
a.
b. Colour change (intensity of one of the colours of either a reactant getting less or a product getting more)
Change in light intensity/ time
b. Temperature change C/time
c. Pressure Change if one gas was produced kPa/time
d. Mass Change g/time
H.Q. 7-9
2.1 Factors Affecting the Rate of Reaction
Factor |
Examples |
1. Temperature - generally hot reactions go faster than cold |
|
2. Concentration – Higher concentrated chemical reactants go faster |
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3. Pressure – gases under pressure are more concentrated |
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4. Nature of Reactants – the atomic structure of chemicals and their geometry affect the way they react |
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5. Catalyst or Inhibitor- a chemical that does not take part in the reaction but speeds it up |
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6. Surface Area – increased number of reactant collisions can occur if there is more surface exposed |
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Note -
Homogeneous Reactions are those whose reactants are in the same phase except solid + solid (because solids come in different forms of the same phase… powder, chunk, crystal…)
Heterogeneous Reactions…. Reactants in different phases
Eg. Solid + liquid, Solid + aqueous, Liq + gas, two liquids that are not mixing (immiscible) like oil and water
Aqueous à Gases and Liquids à Solids
Fastest …........ middle ………. Slowest
HQ 7- 14