chemical synthesis Flashcards
when are reactions faster?
- temp of reactants increases
- size of solid particles smaller, increasing surface area
- concentration of reactions in solution increases
what is the process of crystallisation?
1) dissolving - product in hot water
2) filtering - solid impurities
3) evaporating
4) filtering - crystals
5) drying - crystals in dessicator
what is needed for a reaction to happen?
particles must collide, more collisions faster reaction
what is a catalyst?
substance that speeds up chemical reaction
how does the rate of reaction increase?
- frequency of collisions increases
- with large surface area of solids with high conc of solution
how do chemical engineers control rates?
controlling factors that affect rate
eg:
- temp
- conc
- particle size
what are examples of safety precautions?
4 answers
- gloves + eye protection
- safety screens
- no eating when working with chemicals
- not using flammable chemicals near naked flames
what is chemical synthesis?
give some examples
process which raw materials are made into useful products
eg:
- fertilisers
- paint
- pigments
- food additives
- dyestuffs
what is the formulae of the following salts?
1) sodium chloride
2) potassium chloride
3) sodium carbonate
4) sodium nitrate
5) sodium sulfate
6) magnesium sulfate
7) magnesium carbonate
8) magnesium oxide
9) magnesium chloride
10) calcium carbonate
11) calcium chloride
12) calcium sulfate
1) NaCl
2) KCl
3) Na2CO3
4) NaNO3
5) Na2SO4
6) MgSO4
7) MgCO3
8) MgO
9) NgCl2
10) CaCO3
11) CaCl2
12) CaSO4
what is exothermic reaction?
release energy
- as heat
be dangerous bc can reach high temps if not controlled
what is endothermic reaction?
- less common
- take in energy, so cold to touch meaning products have more energy than reactants
how are salts and water formed?
when acids react with metal oxides, carbonates + hydroxides
when acid reacts with metal carbonate, produces co2
what are examples of salt produced depending on the acid?
- nitric acid, nitrate salts
- sulfuric acid, sulfate salts
what are examples of balanced equations for reactions of acids that produce salts?
hydrochloric acid + sodium hydroxide —> sodium chloride + water
HCl + NaOH —> NaCl + H2O
hydrochloric acid + copper oxide —> copper chloride + water
2HCl + CuO —> CuCl2 + H2O
what is neutralisation?
mixing together acid + alkali in correct amounts so cancel out
acid + base —> salt + water
whats the equation when hydrogen ions from acid react with hydroxide ions from alkali to make water?
H+ + OH- —> H20
what is the equation for when hydrochloric acid and potassium hydroxide neutralise?
hydrochloric acid + potassium hydroxide —> potassium chloride + water
what is the pH scale?
measure of acidity and alkalinity of an aqueous solution across a 14 point scale:
- acids, less than 7
- alkalis, greater than 7
1) how can you detect an acid or alkali?
2) how can you measure the pH of a substance?
1) litmus paper
2) indicator eg universal or pH meter
what is the percentage yield?
when chem synthesis takes place, reactants react to produce new products
greater amount of reactant, greater product formed
how can you calculate percentage yield?
comparing..
- actual yield - actual amount of product
- theoretical yield - expected amount of productactual
————- x 100
theoretical
what is RAM of an element?
shows mass of 1 atom in comparison to the mass of other atoms
(basically top number)
what are the different stages in chemical synthesis of an inorganic compound?
1) establish reaction needed to make reaction
2) risk assessment
3) carry out reaction under suitable conditions eg temp, conc, catalyst
4) purify product to ensure its not contaminated by other products/reactants
5) weigh mass + calculate py
6) check yield + purify by titration
what are the ways of purifying a product?
1) filtration separates insoluble solids from dissolved substances
2) heating evaporates solvent to leave crystals
3) drying in desiccator
what is the RFM of a compound?
RAM of all its elements added together
how do you calculate the RFM?
need to know…
- formula of compound
- RAM of each atom involved
example:
1) MgO
Mg = 24, O = 16 = 40
2) H2O
H2 = 2, O = 16 = 18
how do you find the mass of a product?
1) write equation
2) work out RFM
3) check mass equals mass of products
4) need ratio of mass of reactant to mass of product
5) use ratio to calculate how much produced
what 4 factors speed up the rate of reaction?
- temp
- catalyst
- conc of reactants
- surface area
what happens in a low concentration reaction?
few particles of reactant, and particles spread out so will collide less frequently
what happens in a high concentration reaction?
more particles of reactant, and particles crowded so will collide more frequently
what 3 things does a catalyst do?
- speeds reaction
- makes collisions successful
- lowers energy needed for successful collision
what is an example of different reactions needing different catalysts?
- production of ammonia uses iron catalyst
what are examples of safety factors when carrying out a chemical synthesis on an industrial scale?
- care must be taken to avoid putting harmful by products in environment
- risk assessment
- care must be taken when using reactants that could harm environment if leak
what are examples of economic factors when carrying out a chemical synthesis on an industrial scale?
- py must be high enough to product sufficient daily yield of product
- optimum conditions used that give lowest cost rather than fastest reaction
what does it mean when large particles have a small surface area?
- collisions less frequent so slow reaction
- few particles exposed for collisions
what does it mean when small particles have a large surface area?
- collisions more frequent so fast reaction
- more particles exposed for collisions
how do you analyse a graph about the rate of reaction?
2 things to remember
1) steeper line, faster reaction
2) when reactants used up, reaction stops
why can a reaction be faster than another on a graph?
- catalyst used
- temperature greater
- concentration greater
- surface area greater
what is titration?
used to calculate concentration of acid by finding out how much alkali is needed to neutralise it
what is the method of titration?
1) fill burette with alkali + take reading of volume
2) weight sample of acid + dissolve in a measured volume of distilled water
3) use pipette to measure aqueous acid into conical flask
4) add drops of indicator
5) add alkali from burette to acid in flask drop by drop
6) swirl flask to mix, near end indicator will turn pink. when colour changes permanently = acid neutralised
7) record volume of alkali added by substracting the initial burette reading from final burette reading
how do you collect titration?
need to repeat to make sure its a good estimate of the true value
if 1 result diff, error, repeat or ignore
what is the collision theory?
states for 2 reactants to react, must collide, when they collide, must have enough energy so don’t bounce off each other - called activation energy
if reactant particles collide more frequently, reaction speeds, if particles collide with more energy, more likely to have successful collisions which speed up reaction
what do acidic compounds produce?
aqueous hydrogen ions, H+ when they dissolve in water:
nitric acid - HNO3 - L
sulfuric acid - H2SO4 - L
hydrogen chloride - HCl - G
what do alkali compounds produce?
aqueous hydroxide ions, OH- when they dissolve in water:
sodium hydroxide - NaOH
magnesium hydroxide - Mg(OH)2
what is the formula to analyse titration results?
mass of pure citric acid = 192 x volume x conc / 120,000
then
answer/mass x 100
what different ways can a rate of chemical reaction be found?
1) weighing reaction mixture
2) measuring volume of gas
3) observing formation of precipitate
