topic 7 Flashcards
What would you call an element in group 1 of the periodic table?
Alkali metal
What would you call an element in group 7 of the periodic table?
Halogen
What would you call an element in group 0 of the periodic table?
Noble gas
What are 2 properties of alkali metals? (group 1)
- soft
- relatively low mp and bp
Describe the reaction of lithium with water
lithium floats, fizzes steadily and becomes smaller, until it eventually disappears.
lithium + water → lithium hydroxide + hydrogen
2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
Describe the reaction of sodium with water
sodium melts to form a ball that moves around on the surface. It fizzes rapidly before it disappears.
sodium + water → sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Describe the reaction of potassium with water
the metal melts and floats. It moves around very quickly on the surface of the water. The metal self-ignites. This results in sparks and a lilac flame. There is sometimes a small explosion at the end of the reaction.
potassium + water → potassium hydroxide + hydrogen
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)
What is the pattern of reactivity for alkali metals?
The more electron shells (so the lower in the periodic table) the more reactive the metal
What is the colour and physical state of chlorine at room temperature?
pale green gas
What is the colour and physical state of bromine at room temperature?
brown/orange liquid
What is the colour and physical state of iodine at room temperature?
Grey solid
Describe the trend of physical properties of halogens
The more electron shells (so the lower in the periodic table), the higher the boiling point and the darker the colour
Describe the chemical test for chlorine
damp litmus paper, turns from blue to white (bleached)
Describe the trend in reactivity for halogens
the lower down in the group, the less reactive the halogen (so fluorine is most reactive)
What do hydrogen halides form when dissolved in water?
acidic solutions
When potassium chloride and bromine are mixed, what would the products be?
No reaction would occur as chlorine is more reactive than bromine, so the products would be the same as the reactants.
Why are noble gases inert?
They are in group 0, therefore they have a full outer shell, so they are stable and do not need to gain or lose electrons.
Describe some uses of specific noble gases (give 2)
Argon: filament lamps non-flammable
Helium: balloons
Describe the trend in physical properties of noble gases
As you go down Group 0, the density, melting points, and boiling points all increase.
Define redox reaction
A chemical reaction in which electrons are lost from one substance (oxidation) and added to another (reduction). Oxidation and reduction always occur together.
Mean rate of reaction =
quantity of product formed / time taken
How do reactions occur?
particles of the reactants must collide, when they collide, they must have enough energy for a reaction to occur, the minimum energy needed for a successful collision (so that products form) is the activation energy
When would the rate of reaction increase?
When the frequency of collisions increases
List the 5 things that can be done to speed up the rate of reaction
- Increase temperature
- Increase concentration
- Imcrease surface area (solid)
- Increase pressure (gas)
- Add a catalyst
Define catalyst
A substance that speeds up the rate of a reaction without altering the products of the reaction, being itself unchanged chemically and in mass at the end of the reaction
How does a catalyst increase the rate of a reaction?
By lowering the activation energy of the reaction
Define exothermic reaction
A reaction in which heat energy is given out
Define endothermic reaction
A reaction in which heat energy is taken in
Define activation energy
The amount of energy that the particles of the reactants required for a reaction to occur
Describe the reaction profile for an exothermic and endothermic reaction (include temperature change)
Exothermic: negative temperature change
Endothermic: positive temperature change
Breaking of bonds is ___________
endothermic
Making of bonds is __________
exothermic
Energy change =
Energy of bond breaking - energy of bond making
