C5.2 - Controlling Reaction Flashcards
(16 cards)
What is reaction rate?
- How quickly the reactants are used up or how quickly the products are formed.
What is the formula for reaction rate?
Reaction rate = (amount of reactant used or product formed)/time taken
If the products are gas, describe the method used to find the reaction rate?
Attach a gas syringe to the reaction vessel with a stop, once the reaction has started the plunder will move as the gas is produced.
Note the amount of gas at given time intervals.
Describe a method that uses a mass balance to measure rate of reaction.
- Place your reaction vessel onto a mass balance.
- As the reaction occurs mass will be lost PROVIDED THE PRODUCT IS A GAS.
- Measure the loss in mass at time intervals.
How is mean rate of reaction calculated?
From the two given time intervals, find the gradient.
How is instantaneous rate of reaction calculated?
At the given datum point, draw a tangent and calculate its gradient.
State 2 requirements for a reaction to occur.
- Reactant particles collide with each other
- They have enough energy to react successfully.
What is the effect of an increase in temperature on reaction rates?
- More kinetic energy transferred to the reactant particles
- Particles move faster
- More energy = more frequent collision.
- More particles have enough activation energy or more to conduct the reaction successfully.
- Increase in rate of reaction.
How can reaction times be used?
Reaction time is inversely proportional to rate of reaction so 1/reaction time is rate of reaction s^-1.
What is the effect of an increase in reactant concentration on rate of reaction?
- Reactant particles are more crowded, they are more likely to collide and collide more often.
- Therefore the rate of successful collisions increase increasing the rate of reaction.
- Energy doesn’t change unlike temperature increase where it does.
Describe an investigation that can be used to investigate the effect of concentration on reaction rate.
Mg(s) + 2HCl(aq) > MgCl2(aq) + H2(g)
- Add a known mass of an Mg(s) ribbon to a known volume and concentration of HCl(aq).
- To change concentration, water down the dilute HCl .
- Measure the time taken for each Mg ribbon to dissolve.
- Use 1/time to calculate reaction rate and plot a graph.
What does rate of reaction depend on?
- collision frequency
- energy transfer being enough to conduct a reaction
What effect does an increase in pressure have on reaction rate?
- Particles in a gas state become more crowded, collide more often = more successful collision and faster reaction rate.
- Energy doesn’t change unlike temperature increase where it does.
What effect does smaller surface area of particles have on reaction rate?
- Surface area:volume ratio increased
- More solid reactant particles exposed and more particles reacting for reacting particles to work with to increase reaction rate.
- Energy stored doesn’t change but collision likelihood is more.
What are catalysts, what are their properties and what do they do?
- Catalysts are substances that increase the rate of reaction without being up or changed by lowering the activation energy required.
- Providing an alternative reaction pathway.
In the presence of a catalyst, what occurs in a reaction?
- Greater proportion of particles have activation energy required.
- Rate of successful collisions increase.
- ENERGY DOESN’T CHANGE.
