Rate and Extent of Chemical Change (6) Flashcards
1
Q
What is rate of reaction
A
- a measure of how quickly a reactant is used up, or a product is formed.
2
Q
What is the collision theory
A
- For a chemical reaction to happen:
- reactant particles must collide with each other
- the particles must have enough energy for them to react
3
Q
What is activation energy
A
- the minimum amount of energy needed for a collision to be successful. It is different for different reactions.
4
Q
What does the rate of reaction depend on
A
- Temperature ( When temp is increased, the particles all move around faster, if they move faster they are gonna collide more often, the faster they move the more energy they have, so more collisions will have enough activation energy)
- Concentration of a solution or the pressure of a gas (if there are more particles in a smaller volume then there will be more collisions
- surface area ( its total volume stays the same, the area of exposed surface increases, the surface area to volume ratio increases)
- presence of a catalyst ( a catalyst increases the rate of reaction, having more of these means they will reduce the activation energy needed (this is done by providing a alternative reaction pathway with a lower activation energy))
5
Q
How do you measure rate of reaction
A
- Rate of Reaction = Amount of reactant used up or amount of product formed / time
6
Q
How do you perform the practical for investigating the effect of changing the concentration on the rate of a reaction.
A
- Support a gas syringe with a stand, boss and clamp.
- Using a measuring cylinder, add 50 cm3 of dilute hydrochloric acid to a conical flask.
- Add 0.4 g of calcium carbonate to the flask. Immediately connect the gas syringe and start a stop clock.
- Every 10 seconds, record the volume of gas produced.
- When the reaction is complete, clean the apparatus as directed by a teacher.
- Repeat steps 1 to 5 with different concentrations of hydrochloric acid.
7
Q
How do you perform the practical for investigating the rate of reaction by colour change
A
- Using a measuring cylinder, add 50 cm3 of dilute sodium thiosulfate solution to a conical flask.
- Place the conical flask on a piece of paper with a black cross drawn on it.
- Using a different measuring cylinder, add 10 cm3 of dilute hydrochloric acid to the conical flask. Immediately swirl the flask to mix its contents, and start a stop clock.
- Look down through the reaction mixture. When the cross can no longer be seen, record the time on the stop clock.
- Measure and record the temperature of the reaction mixture, and clean the apparatus as directed by a teacher.
- Repeat steps 1 to 5 with different starting temperatures of sodium thiosulfate solution.
8
Q
How do you calculate the mean reaction rate from a graph
A
overall change in y / time
9
Q
How do you find the rate of reaction from a particular point
A
- by drawing a tangent to the curve
10
Q
What is a reversible reaction
A
- A reaction that can go both ways
11
Q
What is Le Chatelier’s principle
A
- the idea that if you change the conditions of a reversible reaction at equilibrium, the system will try and counteract that change
12
Q
How can changing temperature cause the system to counteract a change
A
- In a reversible reaction, if the reaction is exothermic in one direction, it is endothermic in the other direction. If the temperature is increased, the equilibrium position moves in the direction of the endothermic process
13
Q
How can changing concentration cause the system to counteract a change
A
- If the concentration of a reactant (on the left) is increased, the equilibrium position moves in the direction away from this reactant, and so more of the products are produced (on the right). If one of the products is removed from a reaction (on the right), then the position of equilibrium moves to the right to make more of that product.
14
Q
How can changing pressure cause the system to counteract a change
A
- If the pressure is increased in a reaction involving gases, the equilibrium position moves in the direction of the fewest molecules of gas, to reduce the pressure.
