Chemistry Topic 40, 41, 42, 43, 44

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T40/41- What is an example of an experiment which uses the volume of gas evolved method?
HCl and marble chips. Time is independent variable and volume is dependent variable. THIS TESTS THE IMPACT OF SURFACE AREA
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T40/41- What is an example of an experiment which uses the mass loss through gas method?
Magnesium with dilute hydrochloric acid, (readings at regular time intervals.) Time is the independent variable and mass lost is the dependent variable. THIS TESTS THE IMPACT OF CONCENTRATION.
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T40/41- What is an example of an experiment which uses the precipitate method?
Thiosulfate and HCl. They are both colourless solutions which produce a yellow precipitate of sulfur. You would time how long it takes for a 'marker' to disappear from sight. The independent can be changed from temperature or concentration etc.
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T40/41- How can the decomposition of hydrogen peroxide be used to test rates of reaction?
H2O2 ---> O2 + 2H2O2: Use manganese 4 Oxide as a catalyst. Independent variable is time. The dependent variable is the volume of oxygen given off. THIS TEST CAN BE USED TO INVESTIGATE TEMPERATURE/CONCENTRATION.
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T42- How does temperature have an effect on the collision theory?
More thermal energy means that the particles have more kinetic energy to make more frequent collisions. THERE ARE ALSO FASTER AND MORE SUCCESSFUL COLLISIONS.
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T42- How does concentration or (higher pressure) have an effect on the collision theory?
There are more moles per unit volume so collisions are frequent and more likely.
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T42- How does surface area have an effect on the collision theory?
Particles in the solution around the solid surface can easily collide with the solid. USEFUL COLLISIONS MORE OFTEN.
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T42- How do catalysts have an effect on the collision theory?
They increase the number of successful collisions by lowering the activation energy.
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T42- Describe bond breaking.
It takes in or requires energy so it is an endothermic process.
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T42- Describe bond forming.
It releases energy so it is an exothermic process.
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T42- What name is given to the overall energy change?
Enthalpy change (KJ/mol) Delta H
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T42- What does a positive or negative delta H show?
+ delta H: endothermic because overall it has taken in more energy (to break bonds endothermic,) than it has given out (to form bonds exothermic.) therefore - delta H is exothermic and the opposite happens.
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T43- What would an energy profile diagram look like for a negative enthalpy change?
(EXOTHERMIC.) The reactants are at a higher energy, a small rise for the activation energy, and then a drop in energy as energy is released from forming bonds.
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T43- What would an energy profile diagram look like for a positive enthalpy change?
The reactants would be at a lower energy than the products, as energy is taken in to break bonds.
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T43- What is the activation energy?
The minimum energy needed for the reaction to occur.
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T43- How does a catalyst work?
It speeds up the reaction by providing an alternative reaction pathway WHICH HAS A LOWER ACTIVATION ENERGY. This means another way for the particles to react.
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T43- What does it mean if a reaction is reversible?
The products themselves can react to form the original reactants.
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T43- What is an example of this?
NH4Cl (s) NH3 (g) + HCl (g) Ammonium chloride to ammonia and hydrogen chloride gas
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T43- When will a dynamic equilibrium occur?
If the reaction takes place in a closed system.
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T43- What are the properties of dynamic equilibrium?
The reactions are taking place in both forwards and backward directions AT THE SAME RATE. The relative % quantities of reactants and products reach a certain balance.
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T43- What are the effects of temperature on the dynamic equilibrium?
If you use a higher temperature, the endothermic direction of reaction will increase to take in the heat. If a lower temperature is used, then the exothermic reaction direction will increase to give out more heat.
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T43- What are the effects of pressure on the dynamic equilibrium?
If you increase the pressure, the reaction will favour the direction with fewer molecules. If you decrease the pressure, the reaction will favour the direction where there are more molecules.
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T43- How does the position of equilibrium move?
It moves with the way the reaction if favouring.
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T44- How are different metals naturally found?
Unreactive such as gold exst as their own element, more reactive are usually part of a compound and generally they must be separated from their oxide. (REDUCED.)
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T44- How do the methods of extraction differ?
The metals more reactive than carbon can be extracted by electrolysis. If carbon is more reactie than the metal oxide, then it will more readily take the oxygen from the metal oxide. Therefore IT CAN BE HEATED WITH CARBON MONOXIDE (REDUCING AGENT.)
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T44- What are common properties of both Iron and Aluminium?
They are both dense and lustrous (shiny.) They both have a high melting point and high tensile strength. They are good conductors of electricity and heat. They are malleable.
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T44- What are uses of iron due to its properties?
Wrought Iron (purer iron) is used for decorations and ornamental gates. Cast iron (iron carbon and silicon) is hard but britle (cooking pans and manhole covers.) Steel (iron, carbon and other metals) Hard yet ductile/malleable. Car bodies.
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T44- Why is stainless steel useful?
It is made from iron and chromium so it doesn't rust unlike other compounds with iron in. Therefore it is used in many cooking utensils.
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T44- What are the uses of aluminium and why?
It is used in bicycle frames, aeroplanes and drinks cans, because it does not corrode easily, ( Aluminium reacts quickly with oxygen to form its own top coat layer of aluminium oxide which stops corrosion.) It is also less dense.
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Card 2

Front

T40/41- What is an example of an experiment which uses the mass loss through gas method?

Back

Magnesium with dilute hydrochloric acid, (readings at regular time intervals.) Time is the independent variable and mass lost is the dependent variable. THIS TESTS THE IMPACT OF CONCENTRATION.

Card 3

Front

T40/41- What is an example of an experiment which uses the precipitate method?

Back

Preview of the front of card 3

Card 4

Front

T40/41- How can the decomposition of hydrogen peroxide be used to test rates of reaction?

Back

Preview of the front of card 4

Card 5

Front

T42- How does temperature have an effect on the collision theory?

Back

Preview of the front of card 5
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