groups, rate and reactions Flashcards
what are the group one metals know as
alkali metals
what are the group one metals
lithium, sodium, potassium, rubidium, casesium, francium
what do all alkali metals have
one outer electron, so they have similar chemical properties
what are group ones physical properties
low melting and boiling points
very soft - can be cut with a knife
what do all alkali metals form
ionic compounds
are group one metals reactive and why
very as they really loose the single outer electron, so its easier to loose as it’s only weakly attached to the nucleus so needs less energy to remove it
what do reactions with cold water produce
a hydroxide and hydrogen gas
what happens when you put alkali metals in water
they react vigorously
what happens to the reactivity as you move down the group and why
it increases as the out electron is lost more easily in the reaction, reaction becomes more violent
e.g. lithium will move around the surface vigorously
sodium and potassium do the same however they also melt in the heat
what are group 7 elements know as
halogens
examples of group 7 elements
fluorine, chlorine, bromine, iodine, astatine
chemical properties of group 7
7 electrons in their outer shells, similar chemical properties
exist as diatomic molecules, sharing one pair of electrons in a covalent bond
physical properties of group 7
as you go down group 7 the melting and boiling points increase
what is chlorine at room temp
fairly reactive, poisonous, green gas
what is bromine at room temp
poisonous red / brown liquid which gives off orange vapour
what is iodine at room temp
dark grey crystalline solid which gives off purple vapour
what is the test for chlorine
using damp blue litmus paper, if chlorine is present, it will bleach the paper and turn white
how does reactively change as you go down group 7 and why
decreases as it gets harder to attract the extra electron to fill the outer shell when it’s further away from the nucleus
what can halogens react with
metals and hydrogen
how do halogens mix with metals and what do they form
vigorously and form salts called metal halides
what happens during a halogen displacement reaction
a more reactive halogen will displace a less reactive one
what is a displacement reaction
where a more reactive element pushes out a less reactive element from a compound
what is a halogen reaction
a redox reaction
what is a redox reaction
where a halogen gains electrons (reduction) and halide ions lose electrons (oxidation)
what do displacement reactions shown
reactivity trends
how can you test if displacement reactions show reactivity trends
1) Start by measuring out a small amount of a halide salt solution in a test tube.
2) Add a few drops of a halogen solution to it and shake the tube gently.
3) If you see a colour change, then a reaction has happened - the halogen has displaced the halide ions from the salt.
If no reaction happens, there won’t be a colour change - the halogen is less reactive than the halide and so can’t displace it.
4) Repeat the process using different combinations of halide salt and halogen.
what are group 0 gases
inert, colourless gases / noble gases
facts about group 0 noble gases
- colourless gas at room temp
- all monatomic, gases of a single atom not molecule
- less inert - don’t react much at all
- non flammable
- hard to observe , long time before dicovered
what is argon used for
- filament lamp / light bulb - non flammable as it stops the very hot filament from burning away
- flash photography
- protect metals
what is helium used for
airships and balloons as they have lower density than air and balloons float, non flammable
what are the properties of noble gases
boiling, melting and density all increase as you go down group 0
all react the same way due to the same about of electrons in the outer shells
rate of reaction equ
amount of reactant used up or amount of produced formed / time
how to experiment ways rate of reaction can be measured - precipitation
1) mixing two see-through solutions produces a precipitate, which clouds the solution.
2) You mix the two reactant solutions and put the flask on a piece of paper that has a mark on it.
3) Observe the mark through the mixture and measure how long it takes for the mark to be obscured. The faster it disappears, the faster the reaction.
4) The result is subjective different people might not agree on exactly when the mark ‘disappears’.
how to experiment ways rate of reaction can be measured - change in mass
1) As the gas is released, the lost mass is easily measured on the balance. The quicker the reading on the balance drops, the faster the reaction.
2) You know the reaction has finished when the reading on the balance stops changing,
3) You can use your results to plot a graph of change in mass against time.
4) This method does release the gas produced straight into the room - so if the gas is harmful, you must take safety precautions, The cotton wool lets gases through but stops any solid, liquid or aqueous
e.g. do the experiment in a fume cupboard.
how to experiment ways rate of reaction can be measured - change in volume
1) This involves the use of a gas suringe to measure the volume of gas given off.
2) The more gas given off during a set time interval, the faster the reaction.
3) You can tell the reaction has finished when no more gas is produced.
4) You can use your results to plot a graph of gas volume against time elapsed.
5) You need to be careful that you’re using the right size gas syringe for your experiment though - if the reaction is too vigorous, you can blow the plunger out of the end of the syringe.
how do you measure how surface area effects rate
1) Set the apparatus up as shown in the diagram on the right.
2) Measure the volume of gas produced using a gas surinée. Take readings at regular time intervals and record the results in a table.
3) You can plot a graph of your results time goes on the x-axis and volume goes on the y-axis.
4) Repeat the experiment with exactly the same volume and concentration of acid, and exactly the same mass of marble chips, but with the marble more crunched up.
5) Then repeat with the same mass of powdered chalk.
what do finer particles mean when measuring surface are
higher rate
what does changing the concentration of the acid in measuring surface area mean
affects the rate, more concentration means higher rate
how is rate of reaction affected by temperature
higher temp = higher rate
what does a steeper graph gradient show
faster rate of reaction
gradient equ
change in y / change in x
what needs to happen in order to react (collision theory)
particles must collide with enough energy
what does the rate of a chemical reaction depend on
- collision theory of reacting particles (how often they collide)
the more often the collisions, faster the reaction - energy transferred during collision, particles need to collide with at least activation energy to be successful
what is a catalyst
a substance which increases the rate of reaction however it isn’t used up in the reaction, doesn’t change the products of the reaction
what are biological catalysts
enzymes, they speed to chemical reactions in living cells
examples of reactions where biological catalysts are used
respiration
photosynthesis
protein synthesis
what is an exothermic reaction
one which gives out energy to the surroundings, usually in the form of heat and usually shown by a rise in temp of the surroundings
what is an endothermic reaction
one which takes energy from the surroundings, usually in the form of heat and usually shown by a fall in temperature of the surroundings
what do reaction profiles show
if a reaction is exothermic or endothermic, shows energy levels of the reactants and products in a reaction
what is activation energy
minimum about of energy needed for bonds to break to start a reaction
overall energy change equ
energy required to break bonds - energy released by forming bonds
is a neutralisation reaction endo or exo thermic
exothermic
is a displacement reaction endo or exo thermic
exothermic
is a precipitation reaction endo or exo thermic
exothermic
is a dissolving salts in water reaction endo or exo thermic
depends
some reduce temp - endo
some increase temp - exo
