C2B Flashcards
Examples of slow, moderate and fast?
- Slow - rusting of iron
- moderate - metal reacting with an acid
- fast - reactions in an explosion
What affects rate of reaction?
1, Temp
2, concentration
3. catalyst
4. surface area
What would typical rate of reaction graphs look like?
- slow reaction = not a steep line
* faster rection = steep line that increases quickly and then levels off
How do you measure rate of reaction?
measure how quickly the reactants are used up
OR
how quickly the products are formed
How do you calculate the rate of reaction?
time
Different ways to measure the rate of reactions and explain them
- Precipitation - the solution clouds as the reaction is a precipitate. Mark at base of flask and time how long before it disappears
- Change in mass- usually gas given off. Carried out by mass balance - as gas is released mass is lost
- Volume of gas given off - use a gas syringe and measure amount of gas released. More gas means a faster reaction
Give an examples of rate of reaction experiments
- Hydrochloric acid and marble chips
Break into small or large chunks to judge the affect of surface area - Magnesium metal and dilute HCI
Shows affect of concentration - more concentrated = faster reaction - Sodium thiosulfate and HCI - will produce a cloudy precipitate. Shows that the higher the temp, quicker the reaction
- Decomposition of hydrogen peroxide - shows affect of catalyst
What is collision theory?
The idea that as particles gain more energy they will move/vibrate more which causes more frequent collisions which increases the rate of reaction.
How does collision theory apply to temp, concentration and surface area?
temp - higher temp means more energy which makes particles move quicker = more frequent collisions
concentration - higher concentration means more particles in area = more frequent collisions
surface area - more surface area means more particles and more exposed for solution to work on = more frequent collisions
Whats a catalyst?
substance which speeds up a reaction without being changed or used up
How do catalysts help in industry?
- increase reactions which saves money
- allow reactions to work at lower temperatures
- use less energy
Disadvantages of catalysts
- Used up over time
- can get poisoned
- initially expensive
What is exothermic?
A reaction which transfers energy to the surrounding areas usually in the form of heat and causes a rise in temperature
Example of exothermic reactions?
Combustion
oxidation reactions (sodium to water)
Neutralisation reactions
Exothermic reactions in everyday situations?
Hand warmers - oxidation of iron in air
Self-heating cans - chemicals in base
What is endothermic?
A reaction which takes energy from its surrounding usually in the form of heat which causes a temperature decrease
Examples of endothermic reactions?
Thermal decomposition
Is a reversible reaction endothermic or exothermic?
BOTH
Exothermic in one direction and endothermic in another direction. So the energy absorbed is the equal to the energy released.
What does anhydrous mean?
A reaction that is without water