C2 Part B Flashcards
On which four factors does the rate of a reaction depend?
- Temperature
- Surface area of any solids
- Concentration (or pressure for gases)
- Catalyst
What is the formula for measuring rate of reaction?
Rate of reaction = amount of reactant used OR amount of product formed ÷ time taken
Outline three methods by which the rate of a reaction can be measured.
- By observing a reaction of which the product is a precipitate and timing how long it takes to go cloudy
- By measuring the decrease in mass within a reaction that releases gas
- By measuring the amount of gas given off by a reaction
When the product of a reaction is a precipitate how can rate of reaction be measured?
By observing a mark beneath the transparent beaker where the reaction takes place, and taking note of the time it takes for the mark to totally disappear as the solution becomes increasingly cloudy.
Measuring the speed of a reaction that produces a ……. can be carried out on a mass ……… The quicker the reading on the ….. ….. drops, the faster the rate of reaction.
The volume of gas given off by a reaction can be measured by using a …….. ………, the more gas given off during a certain ……… interval, the faster the rate of reaction.
Measuring the speed of a reaction that produces a gas can be carried out on a mass balance The quicker the reading on the mass balance drops, the faster the rate of reaction.
The volume of gas given off by a reaction can be measured by using a gas syringe, the more gas given off during a certain time interval, the faster the rate of reaction.
Give one advantage and one disadvantage of using either a mass balance or gas syringe method to measure rate of reaction?
Mass balance:
A - Most accurate equipment
D - gas is released straight into the room
Gas syringe:
A - Accurate to the nearest millilitre
D - if the reaction is too vigorous, the plunger can pop out of the syringe.
What is the reaction of hydrochloric acid and marble chips often used to demonstrate?
The effect of surface area on rate of reaction - the reaction wil be faster with smaller pieces of marble chips (or powdered chalk).
This can be demonstrated by using a gas syringe to measure the volume of Carbon Dioxide that is given off.
What is the reaction of magnesium metal with hydrochloric acid used to demonstrate?
How concentration affects rate of reaction. The greater the concentration of acid, the faster the reaction will be.
Sodium thiosulphate and hydrochloric acid are two chemicals, which are both ……. ……. that react together to form a ……… …………
A ……… ……… can be used to change the temperature at which this reaction takes place.
Sodium thiosulphate and hydrochloric acid are two chemicals, which are both clear solutions that react together to form a yellow precipitate (sulfur).
A water bath can be used to change the temperature at which this reaction takes place.
Which catalyst can be used in the decomposition of hydrogen peroxide? And which gas is given off by this reaction?
manganese (IV) oxide
Oxygen is given off, provifing an ideal way to measure the rate of reaction using the gas syringe method.
Which four factors increase the number of collisions in a reaction, and therefore increase the rate of reaction?
- Higher concentration
- Higher temperature
- Larger surface area
- More energy (eg. higher temperature)
Define the term ‘catalyst’
A catalyst is a substance that increases the rate of a reaction, without being changed or used up in said reaction.
List 3 disadvantages of using a catalyst in industry
- They can be expensive
- Most catalysts are very specialist and can therefore only be used for one specific reaction.
- Catalysts can be ‘poisoned’ by impurities and therefore stop working eg. sulfur impurities can poison the iron catalyst in the Haber process
What are the four main advantages of using a catalyst in industry?
- Increases the rate of reaction, product made faster
- Allows the reaction to work at a lower temperature, reduces the energy needed
- Reduces energy needed and therefore cost also
- They don’t get used up easily so can be used over and over again
What is an exothermic reaction?
An exothermic reaction is one which gives out energy to the surroundings, usually in a form of heat and shown by a rise in temperature.
List the 3 main examples of an exothermic reaction
- Burning fuels
- Neutralisation reactions
- Oxidation reactions
What is an endothermic reaction? Give one well known example
An endothermic reaction is one which takes in energy from the surroundings, usually in the form of heat and is indicated by a fall in temperature.
Thermal decomposition is an example of an endothermic reaction
How can reversible reactions be both endothermic and exothermic?
If a reaction is endothermic in one direction, it will be exothermic in the other direction. The energy absorbed in the endothermic direction will be equal to the energy given out in the exothermic direction.
What is the range of the pH scale?
0 to 14
Which pH indicates that a substance is:
a) an acid
b) neutral
c) an alkali
a) From 0 -6
b) 7
c) From 8 - 14
What is a ‘base’? What is an ‘alkali’?
Base = A substance with a pH of greater than 7
Alkali - A base that dissolves in water
What do acids and alkalis form in water?
Acids create H+ ions in water
Alkalis form OH- ions in water