Quantitative chemistry Flashcards
what is concentration
measurement of how many moles of a substance is dissolved in a solvent it is measured in moles per dm3
what is the equation for moles involving mass and Mr
moles = mass divided by mr
what is the equation for concentration involving moles and volume
concentration = moles divided by volume
what is a titration
where an acid reacts with an alkali to give us salt and water
what is an ionic equation
H+ +OH- -> H20 (neutrilization)
what equipment do you need to perform a titration
buretter(unknown concetration
pipette(known concentration)
concial flask
stand
what is step one of performing a titration
use pipette to take 25 cm of the known concentration substance
what is step 2 of performing a titrationn
add an indiator to the conical flask which is phentel phalene
what is an indicator
substance that changes colour in an acid or alkali
what is yield
the mass of the product tjat is made in a chemical reaction
what is the equation for percentage yield
actual yield / theortical yield x 100
what are some reasons why we cant have 100% yield
1.some products will be left behind
2. not all rectants completely react for example in a resible reaction ]
3. sometimes unexpectant [products will happen as a side reaction
4.some product will be lost in separating
5.some of the reactant will not be pure
what is atom economy
the proportion of atoms in the reactants that are covered into useful products reactants with one product will have 100% atom economy
what is the equation for atom economy
rfm of desired products / rfm of all reactants x 100
what is the equation for gas volume including moles and volume
moles = volume / 24 dm 3
what are the conditions of the haber process
iron cataylst,hydrogen and nitrogen
what are the components of air
79% nitrogen , 20% oxygen,0.04% carbpn dioxide and less than 1% of noble gasses - argon,neon
How does the Haber process work
- the two gases,nitrogen and hydrogen will go to the compressor where they will be compressed together
- the compressor is at 200 atmosphere pressure and the tempreturew is 450 degrees
- the combined nitrogen and hydrogen will then go into the reaction vessel
- Iron catalyst will speed up the reaction then it will go into the cooling chamber
- the cooling chamber is where the ammonia will condense into liquid ammonia and any unreacted hydrogen and nitrogen will recycled. The ammonia will be collected for fertiliser
where does nitrogen come from
air
where does hydrogen come from
methane(natural gas
what is a reversible reaction
a reaction in which the product cam also combine to form the reactants
what is equilibrium
the rate at which the foward reaction = the rate of the backward reaction
why can you reach equillirbum in a reversible reaction
you can go both ways,both backward and forward
what is le chatelier’s principle
if a system is at equillibrium and a change is made to any conditions, then the susyem responds to contract the change
where can equillbrium only happen
in an open or closed system where by you are not adding or removing anything from the reaction
what are three factors that effect equllibrium
temperature,concentration and pressure
how does concentration effect equllibrium
- add more reactants mean an increase in concentration of the reactants and causes equilibrium to shift to the right because you have more reactants so they will combine to make products.So the forward reaction will be favoured and you will get more products produced until you reach equilibrium again
- less reactants, equilibrium will shift to the left so the products will combine to make more reactants
how does temperature effect equilibrium
- in every reversible reaction , if one side is exothermic, the opposite side will be endothermic
- expthermic releases energy to the surrounding
3.endothermic takes in energy from the surroundings - the energy is mostly heat energy or thermal
- increase the temperature endothermic will be favoured and would favour the backward reaction,equilibrium will shift to the left
6.decrease in temperature ,exothermic reaction and will favour forward reaction,more product formed
how does pressure effect equillibrium
- always look at the number of moles
222, when you increase the pressure, it will favour the side with more moles,equilibrium will shift to right, reactants will combine to get products,wants more products,favor forwards reaction until you reach equilibrium again - pressure only applies yo gasses because tey are the ones you can compress
what effect does pressure have on the yield of ammonia
causes higher yield of ammonia
what effect does pressure have the rate of reaction
higher/faster rate of reaction
what pressure conditions are used to make a higher yield of ammonia and rate of reaction
high pressure,200 not too high, perfect to increase the yield and rate of reaction
what effect does temperature have on the yield of ammonia
decrease on the yielf of ammonai
what effect does tempreature have on the rate of reaction
higher/faster rate of reaction
what tempreature conditions are used to make a low yield of ammonia and high rate of reaction
medium tempreature
what effect does cataylst have on thhe yielf of ammonia
no effect
what effect does catylst have on the rate of reaction
higher/faster rate of reaction
what cataylst conditions are used to make a high rate of reaction
increase rate no effect on yield
what effect does removing ammonia from the reaction have on the yield of ammonia
higher effect on yielf of amonia
what effect does removing ammonia from the reaction have on the rate of reaction
no effect
what removing ammonia from the reaction conditions are used to make a higher yield of ammonia
equilibrium will shift to the right because of the increase of yield
what is dynamic equillibrium
the rate of the foward reaction = to the rate of the backward reaction and it happens at thee same time
what is fertilliser
a chemical or natural sibstance added to soil or land to improve the growth of plants
nitrogen in the air must be what
fixed into solule nitrates (NO3)
how do you make ammonium nitrate
ammonia + nitric acid
how do you make ammonium phosphate
ammonia + phosphoric acid
how do you make ammonium sulfate
ammonia +sulfric acid
why do plants need nitrogen
for healthy growth
what will happen if we leave the nitrogen in the air
we wont have any nitrate because we are eating the plants
what is nitrogen used for
to make the plants green
what is phosphorus used for
strong roots
what is potassium used for
healthy growth
what is a battery called
a cell
what are 2 or more cells called
battery
what do cells transfers
chemical energy to elecctrical energy and we can use that to power gadgets
what is electricty
the flow of electrons (current)
how do you create the flow of electrons
you beed two metals,one metal that is more reactive than the other,one less reactie than the other and the salt solution because you want to make ions which allows electricity to be conducted
what are simple chemical cells
involves two metals,one more reactive than the other
what does the production of voltage depend on
the type of electrodies and electrolytes
greater the diffrence in reactivity will ……
greater diffrence in reactiveity will produce greater voltage
what will the battery carry
chemical reactoon
what are the two types of batteries
non rechargable and rechargable
how does the inside of a battery work
- the more reacrive the metal is the more oxidised
- the less reactive metal is the more reduced
- in a battery the electrodes are carbon rod and zin casting and carbon will displace zinc
4.ammonium chloride is the electrolyte paste because it is liquid enough to conduct electricity and not liquid enough to fall out the battery
what is a non rechargable battery
ince the reactants are used up the chemical reaction stops for example alkaline batteries
what is a rechargable battery
reactions can be revseed by a suooky with a current and can be used multiple times for example cadiumum batteries
what are fuel cells
- use hydrogen and oxygen
- doesn’t need recharging
- constant supply of fuel
- fuel must be supplied constantly
how do fuel cells work
- in the middle are electrolystes and separate electrodes made of graphite
2.hydrogen is supplied to the negative electrode and the gas will diffuse through the graphite electrode
3.when it diffuses it is going to be reacted with hydroxide Ions to form water#
4.and there will be elections produced and will go to positive electrode where oxygen will gain electrox to form dioxide ions
5.oxygen is supplied to positive electrode and diffuse through graphite electrode and that’s where it will gain that electrons to from the hydroxide ion
what is the half equation for hudrgen at the negative electrode
H2 +2OH- -> 2H20 +2e-
what is the half equation for oxygen at the positive electrode
O2 +2H20 + 4e - -> 4OH
what are three advantages for hydrogen as fuel
- only waste product is water(pollutant)
- fuel cells can be any size for a range of uses
- don;t need to be recharged using electricity
what are three disadvantages for hydrogen as fuel
- hydrogen gas is highly flammable(potinetially toxic )#
- difficult to store/compress
- hydrogen is sometimes produced from ono rechargeable batteries
