Chemistry Flashcards
What is the relative mass of protons,neutrons and electrons
protons=1
neutrons=1
electrons=0
What is the radius of an atom
0.1 nanometers
How do you measure an atoms radius
measure it from the nucleus to the electrons outer orbit
How does an atom become an ion
by losing or gaining electrons to make it balanced
In the periodic table what is another word for the boxes the atoms are arranged in
nuclear symbol
What does the atomic number of an element tell us
how many protons it has and electrons
what does the mass number tell us
how many protons and neutrons in an atom there is
T or F the number of protons and electrons in an atom are the same
True
What is an isotope
an atom with the same number of protons and electrons but a different number of neutrons
What does an element do if it’s isotope isn’t stable
It decays through radiation(alpha,gamma and beta)
What is radioactive decay
where an isotope emits radiation because it it unstable
How do electrons increase to another energy level
if they gain enough energy
How do electrons gain energy to increase to another energy level
from electromagnetic radiation
What happens after an electrons increases to another radiation and why does this happen
it will fall back down,it is not in a stable position because the energy runs out,it then re-emits electromagnetic radiation to it’s surroundings
What is the process of ionisation
where the outermost electrons gains so much energy that it is able to leave the atom completely,this leaves the atom with more protons than electrons which makes it a positive ion
What does ionising radiation mean
that it’s able to knock electrons of atoms
What happens when atoms mix with other substances
they lose the outermost electron and become a positive ion
What are the most reactive group of metals
1
what is the least reactive group of metals
transition metals
What are the measurments to make to when testing reactivity of metals
same mass and surface area and same type and concentration of acid
What will happen if you react metals with water instead of acid
It will form metal hydroxides and hydrogen
What is the idea of displacement reactions
that more reactive metals will replace less reactive ones
Write the reactivity series of metals from most reactive to least
Pottasium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper
What is the non metal in the reactivity series
carbon
What would the outcome be:magnesium sulfate+zinc
no reaction as magnesium sulfate is more reactive than zinc
What would the outcome be:Iron oxide+carbon
=Iron+carbon dioxide
what is the trend with date of discovery with the reactivity series
metals the less reactive metals were found the longest amount of time ago
Why is it that the less reactive metals in the reactivity series were found the longest amount of time ago
because ancient people used charcoal(pure carbon)in a fire/furnace which displaced and made the metals
What does an exothermic reaction do
it gives off heat to the surroundings like a fire
What does an endothermic reaction do
it takes in heat like a snowman
T or F most chemical reactions are exothermic
True
What happens to the activation energy on an exothermic reaction and why
it will increase as the reactants energy level is high
What physical process’s are seen in endothermic reactions
an ice cube melting
what can we measure exo and endo thermic reactions with
a themometer
Describe the process of energy through exothermic reactions
it starts with more energy and ends with less
Describe the process of energy through endothermic reactions
it starts with less energy and ends with more
Describe how freezing and condensation are exothemermic reactions
because bonds need to be made which gives out energy
Describe how melting and boiling and endothermic reactions
because bonds are broken which requires additional energy
When barium hydroxide and ammonium chloride react, the temperature of the mixture decreases. What kind of reaction is this?
This is an endothermic reaction
Why should a polysteyrene cup be used to measure energy change
because it insulates the surroundings from losing or gaining heat to it’s surroundings
If the energy change on an energy level diagram is negative, what does this tell you about the reaction?
It is exothermic
On a reaction profile, what does the height of the hump represent?
the activation energy
T or F thermal decomposition is an endothermic reaction
true
When calcium reacts with water, the temperature changes from 18°C to 39°C.What will the end solution be?
The solution at the end will be alkaline
If a reaction releases more energy when bonds are made than the amount of energy absorbed to break bonds in the reactants.What type of reaction is it?
An exothermic reaction
What does a reaction profile show
a graph that shows the energy of the reaction changing over time
What are the y-axis and the x-axis on the reaction profile
y-axis:the amount of energy the chemicals have got at any particular moment
x-axis:called the progress of reaction
On a reaction profile if the reactants were higher on the y-axis than the products,what reaction is it?
an exothermic reaction
What is the rule of recation profiles to tell if it is exothermic or endothermic
if the product has a higher amount of energy it is endo if the products have a smaller amount of energy than the reactants it is exo
What is the overall energy change on a reaction profile
the difference in energy between the reactant and the product
if the overall energy change is negative on a reaction profile what does it tell us
that it is exothermic
What is activation energy
the minimum amount of energy needed for a reaction to start
In reaction profiles why isn’t the line a straight line and not a curve
because the bonds need to be broken which requires energy
On a reaction profile where is the activation energy
the activation energy is an invisible line from the bit with the least energy to the peak of the curved line
What do catalysts do
they speed up a chemical reaction without it being changed
How do catalysts do their job
they provide an alternative reaction route that has a lower activation energy
How does a catalyst work on a reaction profile
it decreases the activation energy making the peak of the curb smaller
are reversible reactions present in reaction profiles(reactants and products)
yes
What is a reversible reaction on a reaction profile
where reactants can turn into products and vica verca
What is the definition of rate of reaction
the speed at which reactants get turned into products
What is the result of magnesium and acid
a gentle stream of hydrogen bubbles
What are the 2 ways of measuring a rate of reaction
how fast the reactants are being used
how fast the products are being formed
What are the 2 equations for rate of reaction
quantity of reactants used/time taken
quantity of products formed/time taken
What is the reality of the rate of reaction
the answer for it is actually the mean amount of time it has taken
If you measure the rate of reaction in moles how is it different
the time is in minutes not seconds
During an experiment on the rate of reaction what is the best equipment to use to measure the change in mass
a top pan balance
During an experiment on the rate of reaction what is the best equipment to use to measure the gas volume
if the gas is very soluble in water than a gas syringe if not than a inverted measuring cylinder or a burette
what does the reversible reaction symbol mean
that reactants can form products and the products can reform by heating or cooling back into the reactants(vica versa)
If a reversible reaction is endothermic in one direction what is it in the other direction
exothermic
What is equilibrium
a state in which opposing forces or influences are balanced.
What term is used to describe a chemical reaction in which the forward and reverse reaction rates are the same?
a dynamic equilibrium
What is a chemical equilibrium
a state in which the rate of the forward reaction equals the rate of the backward reaction.
What is produced in the backward reaction in this equilibrium, when the reaction goes from right to left: NH4Cl(s) ⇌ NH3(g) + HCl(g)?
The product of the backward reaction is NH4Cl(s).
When a reversible reaction is at equilibrium,what is true
The concentration of products remains constant over time
The equation for the Haber process is: N2 + 3H2 ⇌ 2NH3. What gases will be present at equilibrium?
At equlibrium, there will be a mixture of nitrogen, hydrogen and ammonia. Ammonia has been produced by the forwards reaction.
One of the stages in sulfuric acid production is described by this equation: 2SO2(g) + O2(g) ⇌ 2SO3(g). What will happen to the yield of SO3 if the pressure is increased?
It will go up, because the equilibrium position moves in the direction which forms the fewest molecules of gas.
If the forward reaction in a reversible reaction is endothermic, what will be the effect of decreasing the temperature?
It decreases the amount of product present at equilibrium
What is the effect of decreasing the pressure on the following equilibrium 2NO(g) + O2(g) ⇌ 2NO2(g)?
more NO2 will be formed as the equilibrium will shift in the movement which has more gas molecules
What effect on the equilibrium position is produced by adding a catalyst to a system in equilibrium?
it will have no effect as a catalyst speeds up the forwards and backwards direction of the reaction
What does the mass no. tell us
how many protons and neutrons it has
what does AR stand for and what does it mean
it is the relative atomic mass which means it is the average mass of all the isotopes of the element
Explain why chlorine has a relative atomic mass of 35.5
the isotopes are 35 and 37 which added and divided by 2 equal 35.5
What is MR and what is it
it is relative formula mass,you use it if you want to find all the isotopes in a compound
How do you find the relative formula mass
add together the relative atomic masses of all the compounds in that molecular formula
What would the relative formula mass of magnesium chloride be
24+35.5(x2)=95
What is the % mass of sulfur in Sulfuric acid(H2SO4)
AR of sulfur X no. of sulfur/MR of compound
32 X 1/98 X100=32.7%
What is ionic bonding
Ionic bonding occurs between metal and non-metals. The metal loses electrons to form a positive ion and the non-metal gains electrons to form a negative ion.
What is covalent bonding and when does it occur
A chemical bond formed when electrons are shared between two atoms.It typically occurs between 2 non-metals
Give an example of covalent bonding
if there were 2 hydrogen atoms both of them would need 1 more electron to be stable,to make them stable they form together
What is metallic bonding
where the metal ion stays still and vibrate and delocalised electrons can move freely throughout it
What is the metal with the highest melting point and what does it make it useful for
Tungsten(3339)it is used for filaments in a light bulb
What are alloys used for
breaks up the regular structure of a metal atom
How do you make an alloy
by inserting different sized atoms
What are alloys
they are harder than original metals because the irregulatiry of the structure helps stops rows of atoms from slipping over each other
What are the 2 allotropes of carbon
fullerenes and graphene
What are allotropes
different structural forms of the same element in the same physical state
What is graphite made up of and what is it’s structure
graphene,multiple repeating hexagons with each carbon being bonded to 3 others
How can graphene conduct electrcity
because one of it’s atoms donates it to a pool of delocalised electrons
What are fullerenes
shapes made out of grapite like tubes or spheres
How are fullerenes spheres useful and why is this
for example with drugs they can use it to form a sphee to act like a cage to deliver it to certain parts of the body,industrial catalysts because of their high surface area:volume
What are the fullerene tubes used for and why is this
nanotechnology,electronics,to strengthen other materials(tennis racket frames),this is because of their high length:diameter ratio
What was the first fullerene made and what is it
the buckminster fullerene-a hollow sphere made of 60 carbon atoms
formula:C60
what is nanotechnology used in
medicine,batteries,fashion and food
How are ions formed
when atoms lose or gain electrons
What is an ionic compound
it is made up of charged particles called ions
T or F ionic bonds are really strong
true
What is oxidation
the process of gaining oxygen
What is reduction
the process of losing oxygen
How are metal oxides form
as most metals are quite reactive they react with the oxygen which oxidises it
T or F most metals are oxidised
true
What are the exceptions to metals being oxidised
metals like gold as they are very unreactive
What is the cheapest and easiest way to make pure metals and how does it work
to direct the metal oxides with carbon,the carbon takes the oxygen to form carbon dioxide to leave behind a pure metal
When making pure metals why can’t you use the carbon method all the time
it only works on the metals that are less reactive than carbon
Why is carbon placed in the reactivity series
when making pure metals the carbon method only works on the metals less reactive than carbon
How do you make pure metals if the metal is more reactive than carbon
through a process called electrolysis but it is really expensive
What is the most common iron ore
FE2O3
What is the haber process
the industrial production of ammonia from nitrogen and hydrogen
Why is the haber process one of the most important reactions in the world
because the ammonia it produces is used to make nitrogen based fertilisers which grows all the food we need
For the haber process we need huge amounts of ammonia,how do we aqquire this
we would need lots of nitrogen and hydrogen
nitrogen is easy to get as it is 78% of our atmosphere
hydrogen is harder to get as we have to get it from hydrocarbons like methane
What type of reaction is the haber process and what does that make it
exothermic as it produces heat so it would be reversible
How does the haber process work
take the hydrogen and nitrogen and feed it in to the top left of the machine so they can mix together this happens at the reaction vessel,under the conditions in the reaction vessel they react to form ammonia but because it is a reversible reaction there will still be a lot of nitrogen and hydrogen
What is in the haber process machine
where the nitrogen and hydrogen enter is called the reaction vessel,it is kept at 450 degrees and has 200atm,there is a tube in it which is where the iron catalyst is
how do we separate the nitrogen and hydrogen from the ammonia
ammonia has a low boiling point,so in the machine it is passed into the condenser which will cool down the gaseous ammonia into liquid ammonia,and the hydrogen and nitrogen will stay as gasses as they have high boiling points
In the haber process why does the temp need to be kept at 450 degrees
because it is an exothermic reaction we will need a lower temp to favour the forward reaction and to keep a higher % yield but it has to be 450 as for the rate of reaction the temp needs to be high and very high temp’s would be very expensive
What are the 3 things to consider in the haber process
% of yield
rate of reaction
cost
In the haber process why does the pressure need to be 200 atm
to achieve a high % of yield you need a high pressure a high amount of pressure would also achieve a high rate of reaction(makes particles collide more frequently)it has to be at 200 amp because maintaining a high pressure is expensive or can be very dangerous
Fertilisers typically contain three essential elements. What are they?
nitrogen,phosphorus and pottasium
Which essential elements are provided by the fertiliser potassium nitrate, KNO3?
Potassium nitrate contains potassium and nitrogen
What useful compound is produced when phosphate rock is reacted with phosphoric acid?
Triple superphosphate (calcium phosphate) is made when phosphate rock is reacted with phosphoric acid.
What is ammonia reacted with to produce nitric acid?
Ammonia, NH3, is oxidised to form nitric acid, HNO3
Which two reactants are needed to make ammonium sulfate in the laboratory?
Ammonia + sulfuric acid → ammonium sulfate.
