1526030
Descrição
Mapa Mental por andrewstalker, atualizado more than 1 year ago
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Criado por andrewstalker
aproximadamente 10 anos atrás
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Rate of reaction 1;
Reaction times and rates
- Some reactions are fast and some are slow.
- Rusting is slow reaction.
- burning/explosions are fast reactions
- Rusting is slow reaction.
- measuring the product formed depends on weather it is solid or gaseous.
- solids are measured in Grams
- gasses are measured in cm3
- The period may be chosen upon the rate of reaction. if it is a slow
reaction then g/min or if it is a fast reaction it should be cm3/s.
- solids are measured in Grams
- The volume of gas is usually
measured in a gas syringe.
- In a typical rates experiment, the mass or volume of
product is measured at regular time intervals. It is
usual to record these results in a suitable table
- The results show that the reaction had finished by 4
minutes, as no more gas was produced after that
- The mean rate of reaction
= 50 ÷ 4 = 12.5 cm3/min
- The mean rate of reaction
= 50 ÷ 4 = 12.5 cm3/min
- However, the rate decreases during the
reaction. The analysis below shows how.
- The results show that the reaction had finished by 4
minutes, as no more gas was produced after that
- The rate of reaction can be analysed by plotting a
graph of amount of product against time. The
graph below shows this for two reactions
- Compared to the slow reaction, the graph line for the faster
reaction: Has a steeper gradient at the start and becomes
horizontal sooner (showing that the reaction time is less)
- Compared to the slow reaction, the graph line for the faster
reaction: Has a steeper gradient at the start and becomes
horizontal sooner (showing that the reaction time is less)
- limiting reactants
- A reaction stops when all the particles of one of the
reactants are used up. In a reaction involving two reactants
- The limiting reactant is the one that is
all used up at the end of the reaction
- The limiting reactant is the one that is
all used up at the end of the reaction
- The reactant in excess is still there at the end of the
reaction (although in a smaller amount than at the start)
- For example, magnesium reacts with hydrochloric acid; Magnesium
is the limiting reactant if it is all gone at the end OR hydrochloric acid
is the limiting reactant if some magnesium is left at the end
- reactions happen when particles collide with enough
energy. The more reactant particles there are to begin
with, the more can be formed. this is why the limiting
factor is directly proportional to the product formed.
- A reaction stops when all the particles of one of the
reactants are used up. In a reaction involving two reactants
- The amount of product formed in a reaction is directly
proportional to the amount of limiting reactant used
- This means that a graph showing
amount of product formed against
amount of limiting reactant will give a
line that is straight, has a positive
gradient & passes through the origin (0,0)
- This means that a graph showing
amount of product formed against
amount of limiting reactant will give a
line that is straight, has a positive
gradient & passes through the origin (0,0)
- The rate of reaction can be calculated from the gradient
of a graph of amount of product against time of reaction
- 1.) Draw a tangent to the curve (a straight line
that represents the gradient at that point)
- 2.) Draw a vertical line and horizontal line to form
a right-angled triangle with the line from step 1
- 3.) Read off the change in amount of
product (the vertical line in your
triangle)
- 4.) Read off the change in time (the
horizontal line in your triangle)
- 5.) Calculate the gradient. This will be the answer
from step 3 divided by answer from step 4
- 5.) Calculate the gradient. This will be the answer
from step 3 divided by answer from step 4
- 4.) Read off the change in time (the
horizontal line in your triangle)
- 3.) Read off the change in amount of
product (the vertical line in your
triangle)
- 2.) Draw a vertical line and horizontal line to form
a right-angled triangle with the line from step 1
- In the example; rate of
reaction = 10.4 ÷ 2 = 5.2 g/min
- 1.) Draw a tangent to the curve (a straight line
that represents the gradient at that point)
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