Flashcards in Chemistry 6 Deck (65)
What four things affect rate of reaction ?
Surface area of solids
In what state does pressure affect rate of reaction ?
How can you find the rate of reaction ?
Amount of reactant used or amount of product formed divided by time
Give three ways rate of reaction can be measured ?
Change in mass
Volume of gas given off
How do you measure rate of reaction with precipitation ?
Place a cross, or mark, below the solution and time how long it takes before the mark is no longer visible
What do you look for when measuring a change in mass ? How do you find this ?
You are looking for a change in the mass, the quicker the change the faster the rate of reaction. To find this you place the solution on weighing scales and let the reaction take place
What piece of equipment measures the volume of gas given off ?
A gas syringe
How is the volume of gas given off in a reaction measured ?
A gas syringe measures the gas given off by collecting it as it leaves the beaker. The more gas given off the faster the rate of reaction
What is an example of an experiment that measures volume given off ?
The reaction of hydrochloride acid and marble chips
Name a reaction that is good for measuring a change in mass
Magnesium metal with dilute hydrochloric acid
What does the decomposition of hydrogen peroxide show ?
The effects of different catalysts on rate of reaction
What catalyst speeds up the decomposition of hydrogen ?
Manganese (IV) oxide catalyst
What is collision theory ?
More collisions between particles increases the rate of reaction.
How does temperature increase rate of reaction in regards to collisions ?
When the temperature increase the particles gain energy and move quicker. If they move quicker they will collide more often
How does higher concentration increase collisions ?
If there is a higher concentration there are more particles in the same amount of space. Therefore they are more likely to collide as the space becomes confined
Why does a smaller surface area increase the rate of reaction ?
The particles, when smaller, have a larger area to work on so they can collide with more things and more frequently
What is a catalyst ?
A catalyst is a substance which speeds up a reaction, without being changed or used up in the reaction
How does using a catalyst reduce cost in industrial reactions ?
• By increasing rate of reaction the plant doesn't need to operate for so long because it happens quicker
• Works at a lower temperature, reducing energy costs
What are the disadvantages of using catalysts ?
• They are expensive
• they can be 'poisoned' by impurities and stop working
What is an exothermic reaction ?
A reaction which transfers energy to the surroundings, usually in the form of heat and shown by a rise in temperature
What is the best example of an exothermic reaction ?
Combustion - it gives out a lot of heat through burning
What is an endothermic reaction ?
A reaction which takes i energy from the surroundings, usually in the form of heat and shown by a fall in temperature
What is a good example of an endothermic reaction ?
If a reversible reaction is endothermic one way, what will it be the other way ?
Exothermic, the energy absorbed one way is equal to the energy released the other
What number is neutral on the pH scale ?
What numbers are acids on the pH scale ?
What numbers are alkalis on the pH scale ?
What is an indicator ?
A dye that changes colour depending on whether it's above or below a certain pH
What are substance with a pH of greater than 7 also known as ?