C-6 The rate and extent of chemical change Flashcards
1
Q
- What is the the rate of reaction
A
- How fast the reactants are changed in products
2
Q
- what are the equations used to calculate rate of reaction
A
mean rate of reaction =
quantity of reaction used//time taken
Sanity ion product formed// time taken
3
Q
What must happen in order for a reaction to take place
A
- Must collide with enough energy
-
4
Q
What is collision theory
A
- The more collisions there are the faster the rate of reaction
- the energy transferred during a collision. Particles have to collide with enough energy for the collision to be successful
- Activation energy- the amount of energy needed to break to bonds
5
Q
What increases the rate of reaction on a theory basis
A
- More collisions increase the rate of reactions
6
Q
How does temperature effect the rate of reaction
A
- When temperature increase the kinetic energy store increases and they move faster
- As they are moving faster they will collide more frequently
- The faster they move the more energy they gave so more collisions will have enough energy to make the reaction happen
7
Q
What effect does concentration and pressure have on a reaction
A
- IF a solution is more concentrated it means there are more particles knocking about in the same volume of water
- Similarly when pressure increases it means same number of particles occupy smaller space
- makes collisions more frequent- therefore rate of reaction increases.
8
Q
What effect does surface area have on rate of reaction
A
- IF reactants is solid then breaking it up will increase surface area to volume ratio
- This means that for the same volume of solid particles will have more area to work on- so reactions will be more frequent
9
Q
- What is a catalyst
A
- Substance that speeds up a reaction without being used up itself within the reaction - not part of overall equation
- Different catalysts are needed for different reactions- but they all decrease activation energy- provide an alternate pathway- lower energy needed
10
Q
- How do catalysts effect the rate of reaction
A
- Different catalysts are needed for different reactions- but they all decrease activation energy- provide an alternate pathway- lower energy needed
11
Q
- What are enzymes
A
- Biological catalysts - speed up rate of reaction in living things
12
Q
- What are the steps in measuring change in rate of reaction
A
- Colour change and precipitation
- Change in mass- gas
- Volume of gas given off
13
Q
How do you investigate rat elf rate of reaction in precipitation and colour
A
- Visual change
- Observe a mark through solution and see how ;omg to tales to disappear- faster it takes faster rate
- If reactants are coloured and products colourless you can see how long it takes to gain or loose colour
- Subjective results
- Cant plot
14
Q
How do you investigate rate of reaction using change in mass
A
- measuring speed that produces a gas
- As gas is related the mass leaving is measured in change in mass balance
- IF take measurements at regular intervals a graph can be plotted
- Most accurate- gas goes into room
15
Q
- How do you investigate rate of reaction using gas syringe
A
- Gas given off
- More gas given off means faster rate
- nearest cm 3
- Graph
- Can low plunger out
16
Q
What is the two rates experiments method
A
- Add set volume of HCL to conical flask
- Add magnesium while on a mass balance
- Record mass change at set intervals
- Test with other concentrations
- Plot on same graph and compare
17
Q
- What is is the black cross test
A
- Both clear- go yellow
- Add set amount of sodium
- Place piece of paper in
- Test time to no longer see black cross for different concentrations
- No graph
18
Q
- How can you calculate mean rate of reaction
A
- Overall change//overall time
19
Q
- How do you find rate of reaction at a particular point
A
- Draw a tangent and find relative gradient
20
Q
- What are reversible reaction
A
- In some chemical reactions the products can react to produce original reactants
21
Q
- How can reversal reactions be represented
A
- A + B <=> C + D
22
Q
- How can the direction of reversible reactions be change
A
- By changing the conditions
e. g Ammonium chloride <====> Ammonium+ hydrogen
to move left to right - heat
to remove left to right- cool
23
Q
- What are the energy changes in a reversible reaction
A
- A reversible reaction is endothermic in one direction and exothermic in another. Same amount of energy transferred
24
Q
- What is an example of exothermic and endothermic reversible reactions
A
- Hydrated copper sulfate <=====> Anhydrous copper sulfate+ water
Left to right- endothermic
Right to left- exothermic
25
Q
What is an equilibrium
A
- When a reversible reaction occurs in apparatus that prevents the escape of reactants and products
26
Q
When is equilibrium reached
A
Equilibrium is reached when the forward and reverse reactions occur at exactly the same rate
27
Q
What do the relative amounts of reactants and products depend on in an equilibrium
A
- The conditions
28
Q
What happens if there is a change to a system that is in equilibrium
A
- The system responds to correct it
- La chandelier’s principle
29
Q
How does a system respond to temperature change
A
- All reactions are endothermic one way and exothermic another
- IF you decrease the temperature- equilibrium will move towards the exothermic in order increase the temperature- more products for endothermic- less for exothermic
- IF you Increase the temperature the equilibrium will move towards endothermic in order to decrease the temperature. More products for Endothermic. Less for Exothermic
30
Q
How does a system respond to a pressure change
A
- Only relevant for gases
- IF pressure is increased to try and reduce it it moves towards state where less molecules are present
- If pressure is decreased it will move towards state where more molecules re present
31
Q
- How does a system respond to concentration increase
A
- If you increase concentration it will no longer be at equilibrium
- System attempt to bring it back
- IF increase in concentration of reactions- shift towards products
- If increase in products- shift toward reactants
