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Industrial Chemical Synthesis

Chemical synthesis term used to describe process of making complex compounds from simpler ones

Most chemicals have been carefully researched, formulated and tested by chemists

Examples:

Food additives- chemical industries make preservatives, flavourings and colourings

Cleaning and decorating products- like paint and pigments and dye in it or bleach and oven cleaner been formulated by chemists

Drugs- Made by pharmaceutical companies most common drugs like paracetamol have gone through lots of development and testing

Fertilisers- 1 mil tonnes of fertilisers made each year, lots of ammonia used which is made by chemical industry

Not only do chemists have to figure out how to make chemicals, but also in a way that produces the highest yield (by controlling the rate of reaction) also need to think about how environment and producing least amount of waste

Chemical industry huge

Scale- some chemicals made on a HUGE scale e.g sulfuric acid other chemicals e.g pharmaceuticals produced on smaller scales but doesn't mean we don't need them just means we need less of them

Acids and Alkalis

Pure acidic compounds can be solid- citric acid, liquid- sulfuric acid or gas- hydrogen chloride

Common alkalis include sodium hydroxide

Indicators and pH meters can be used to determine a pH

Indicators contain dye that changes colour depending on substance

Litmus paper is easy way to find out whether substance is acid or alkali (red= acid blue=alkali)

Universal indicator can also be used and gives an estimate of the number on the pH scale

pH meters are the most accurate- probe dipped in substance and then gives a reading of the pH

Neutralisation Reactions: acid and alkali mixed together make a salt

Acid is a substance with a pH below 7 and produces aqueous hydrogen ions H+ in water

Alkali is a substance with a pH above 7 and produces aqueous hydroxide ions OH- in water

When acid and alkali react together they form salt and water

Products are neutral

Neutralisation can be seen in terms of the equations: H+ (aq) + OH- (aq) ----> H20 (l)

Acids Reacting with Metals

Acid + Metal ----> Salt + Hydrogen

More reactive the metal the faster reaction will go- some react explosively

Copper doesn't react with acid at all because it's less reactive than hydrogen

Speed of reaction indicated by rate at which bubbles given off

Hydrogen confirmed by using the squeaky pop method

Name of salt produced uses name from acid and metal

E.g Hydrochloric acid always produces chloride salts, Sulfuric acid produces sulfate salts

Oxides, Hydroxides and Carbonates

Acid + Metal Oxide ----> Salt + Water

Acid + Metal Hydroxide ---> Salt + Water

Combination of acid and metal decides name of salt

Metal carbonates give salt + water + carbon dioxide

Synthesising compounds

7 stages involved in chemical synthesis

Choosing the reaction: Chemists need to choose the reaction to make the product e.g neutralisation- acid and alkali make a salt, thermal decomposition- heat used to break up compound into simpler substances and precipitation- an insoluble solid formed when two solutions are mixed

Risk Assessment: involves identifying hazards, assessing who might be harmed and what action can be taken to minimise risk

Calculating the Quantities of Reactants: Using maths and balanced symbol equations to calculate how much of each reactant is needed to produce a certain amount of product. Important in industry so you can know exact amount of raw material and not to waste any

Choosing the Apparatus and Conditions: Right apparatus needs to be used and correct size and strength. Chemists also need to decided what temp the reaction should be carried out in and concentration and should a catalyst be used or not

Isolating the Product: After the reaction is finished products may need to be separated from reaction mix. Could use evaporation, filtration or drying

Purification: As your isolating the product you are also purifying it

Measuring Yield and Purity: Yield tells you overall success of the process. Compares what you think you should get with what you get in practice. Purity of chemical needs to be measured.

Purification and Measuring Yield

Isolating product and purification use similar techniques

Filtration: Used to separate insoluble solid from liquid. Pharmaceutical industry uses filtration to separate out aspirin. Can be used for purification too because solid impurities filtered out

Evaporation and Crystallisation: Used to separate soluble solid from solution Heating up solution causes liquid to evaporate leaving behind the solid crystals. Crystals have regular structure that impurities can't fit into which is why it helps to purify the product. Process repeated many times to increase purity, products dissolved and then crystallised again (called recrystallisation)

Drying: Used to dry product by removing excess liquid. Products can be dried in drying oven. Some just heat the sample others blow hot dry air over product. Some use desiccators- containers that contains chemicals like silica gel that remove water from their surroundings

Percentage yield: Actual yield: Mass of pure dry product. Calculated by weighing product Theoretical yield: Maximum possible mass of pure product that could be made using amount of reactants used. Calculated from the balanced symbol equations and the relative formula mass. Percentage yield: (Actual yield/ Theoretical yield) x 100 Always will be less than 100% due to the loss of product along the way

Titrations

Titration can be used to check purity of acidic or alkaline products

First add known volume of alkali to titration flask with 2 or 3 drops of indicator

Fill a burette with acid

Using burette, add acid to the alkali a bit at a time (swirling regularly)

Indicator changes colour when all alkali has been neutralised

Record volume of acid used to neutralise alkali

Solids weighed out into a titration flask:

First solid must be crushed into powder

Put titration onto balance

Weigh some of powder into flask

Add a solvent (e.g water or ethanol) to dissolve powder

Finally swirl titration flask until all solid has dissolved

Purity

Some products need to be very pure

Purity of product will improve as it's being isolated

Purity is important in pharmaceuticals and petrochemicals

Energy Transfer in Reactions

Exothermic: a reaction which gives out energy to the surroundings usually in the form of heat usually shown in rise of temperature

Endothermic: a reaction is one which takes in energy from the surroundings usually in the form of heat shown by fall in temperature

Chemical synthesis, Acids+alkalis, acids reacting metal

OX,hydrox+ carb + synthesisng compounds+purification

titration + purity + Enrgry transfer in reactions