Rates of Reaction Flashcards
What factors can affect the rate of reaction
- surface area
- temperature
- pressure
- concentration
- use of catalyst
Describe the effects of changes in the surface area of a solid to the rate of reaction
- increasing surface area means there are more places for particles to collide
- this leads to an increased frequency of collisions between the particles
- resulting in a faster rate of reaction
Describe the effects of changes in the temperature of a solid to the rate of reaction
- when particles are heated they have more kinetic energy and move around more
- this leads to an increased frequency of collisions between the particles
- resulting in a faster rate of reaction
Describe the effects of changes in the pressure in a gas to the rate of reaction
- increasing pressure means there are more particles in a given volume
- this leads to an increased frequency of collisions between the particles
- resulting in a faster rate of reaction
Describe the effects of changes in concentration on the rate of reaction
- increasing concentration means there are more particles in a given volume
- this leads to an increased frequency of collisions between the particles
- resulting in a faster rate of reaction
Describe the effects of using a catalyst on the rate of reaction
- using a catalyst provides an alternate route for the reaction with a lower activation energy
- this increases the proportion of particles with energy to react
- resulting in a faster rate of reaction
What is a catalyst?
Catalysts are substances that speed up chemical reactions without being changed or used up during the reaction
- they do not appear in equations as they do not change the final product, only the rate at which the reaction happens
Test for oxygen
- glowing splint relights
Test for hydrogen
- squeaky pop over a lit splint
Test for carbon dioxide
- bubble through limewater
- should turn cloudy
What are the ways to measure the rate of a reaction
- mass loss at regular time intervals (using a balance scale)
- volume produced at regular time intervals (using a gas syringe)
- decreasing light (record time for cross to disappear)
What experiment can be used to prove temperature affects the rate of reaction?
Sodium thiosulfate experiment
In the sodium thiosulfate experiment, what is the:
- independent variable
- dependent variable
- control variables
- possible errors and solutions
- temperature
- time taken for cross to disappear
- concentration + volume of thiosulfate solution and acid
- judgement of cross (use same person)
- inaccuracy of temperature (water bath)
- error in measuring acid (small increments at eye level)
- judgement of cross (use same person)
What is the equation (word and symbol) for the sodium thiosulfate experiment
- Sodium thiosulfate + hydrochloric acid = sodium chloride + sulphur dioxide + sulphur + water
- Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + SO2(g) + S(s)
What experiment can be used to prove concentration affects the rate of reaction?
Magnesium chloride experiment
In the magnesium chloride experiment, what is the:
- independent variable
- dependent variable
- control variables
- concentration
- rate of the volume of gas produced at regular time intervals
- -volume of acid (measure with a measuring cylinder)
- mass of magnesium (weigh using a balance)
- type/size of magnesium
- temperature (same room and time)
What is the equation (word and symbol) for the magnesium chloride experiment
- magnesium + hydrochloric acid = magnesium chloride + hydrogen
- Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
What experiment can be used to prove surface area affects the rate of reaction?
Marble chips experiment
In the marble chips experiment, what is the:
- independent variable
- dependent variable
- control variables
- surface area of the marble chips
- rate of mass loss over time (at regular intervals)
- -volume of acid (use measuring cylinder)
- mass of chips (weigh using a balance)
- concentration of acid (use same conc)
- temperature (same room and time)
Why is cotton wool used instead of a bung
- cotton wool lets gasses escape but not any solution so prevents spillages
What is the equation (word and symbol) for the marble chips experiment
- Calcium carbonate + hydrochloric acid = calcium chloride + carbon dioxide + water
- CaCO3 + 2HCl → CaCl2 + H2O + CO
Describe a method for finding out the effect of surface area on rate of reaction
- weigh x amount of marble chips (calcium carbonate) into a conical flask and place onto a balance
- using a measuring cylinder, measure y amount of hydrochloric acid
- add all acid to the flask, placing cotton wool on the top and start the timer
- record mass of reaction every z seconds for at least v minutes
- repeat experiment using small marble chips
Describe a method for finding out the effect of concentration on rate of reaction
- measure x grams of magnesium using a balance and add to a conical flask
- using a measuring cylinder, measure y amount of hydrochloric acid
- add all acid to the flask and start the timer
- read off and record the volume of the gas syringe every z seconds for at least v minutes
- repeat experiment using a higher concentration of acid
Describe a method for finding out the effect of using a catalyst on rate of reaction
- Set up the apparatus. Fill the measuring cylinder with water and hold it in position with a clamp.
- Measure x cm3 of water using a measuring cylinder and pour into the conical flask.
Measure y cm3 of 20-volume hydrogen peroxide solution using a small measuring cylinder. Add this to the conical flask. - Add a large spatula load of manganese dioxide powder to the flask.
- Swirl and immediately fit the stopper and start the clock.
- Note the time take to fill the measuring cylinder with gas. Record the results in the table below. Repeat the experiment with different catalysts.
Catalyst experiment word and symbol equation
Hydrogen peroxide = water + oxygen 2 H2O2(l) = 2 H20() + O2(g)
