Rates of reaction Flashcards
On a rate of reaction graph what does the line getting steeper show?
The rate of the reaction is increasing
What does a flat line on a graph of amount of products against time show?
A flat line shows that all the products have been formed
What two factors relating to the collisions between particles influence the rate of the reaction?
Collision frequency and energy transferred during a collision
What are the four factors that affect the rate of a chemical reaction?
Temperature, Pressure/Concentration,Surface area and the presence of a catalyst.
Why does increasing the temperature of a reaction mixture increase the rate of the reaction.
Particles are moving faster and therefore will collide more frequently. They also transfer more energy when colliding.
Other than increasing the temperature, describe two ways of increasing the rate of reaction between a solution and a solid.
Increase the surface area to volume ratio of the solid by breaking it up into smaller pieces. Particles will have more area to work on so there will be collisions more frequently.
Using a catalyst to lower the activation energy, so less energy is required and the reaction happens faster.
What is a catalyst, and how do they work?
A catalyst speeds up the rate of the reaction without being used up. It works by decreasing the activation energy needed. They do this by providing an alternative reaction pathway with lower activation energy.
State the equation that could be used to calculate the mean rate of reaction
Rate of reaction=Reactants used or products formed/time
Give three possible units for the rate of reaction
g/s
mol/s
cm3/s
How would you measure the rate of a reaction between two clear solutions, in which the product formed was a precipitate?
You can observe a mark through the solution and measure how long it takes for it to disappear. You can also time how long it takes for a solution to lose or gain its colour.
Why is measuring a mass change during a reaction an accurate method of measuring rate?
Mass balance is very accurate.
Describe how you could investigate the effect of increasing HCl concentration on the rate of reaction between HCl and Mg.
Add HCL to conical flask and place on a mass balance. Add magnesium ribbon and plug the flask with cotton wool. Start the stopwatch and record the mass on the balance at regular intervals. Change the acids concentration only.
Describe how you could use a graph to find the mean rate of a reaction between two points in time.
Change in y divided by change in x
How could you use a tangent to find the gradient of a curve at a particular point?
Draw a tangent to the curve only touching at the point you are trying to find and calculate the gradient of the tangent.
If the forward reaction in a reversible reaction is exothermic, what is the reverse reaction?
Endothermic
