Chemistry C4 - C6 Flashcards

Question

Alloys (Triple)

Answer 1

An alloy is a mixture of a metal and other elements. Steel is an alloy of iron and carbon - A lot harder and stronger (wont rust either) Brass - Copper and Zinc Bronze - Copper and Tin Solder - Lead and tin Duralumin - 94% aluminium, 4% copper, 1% of magnesium and small amounts of manganese

Answer 2

Rusting of iron is a redox reaction. Iron + oxygen + water --> hydrated iron(III) oxide Iron loses electrons when it reacts with oxygen to become Fe3+ so it's oxidised Each O atom gains two electrons to become O2-, so oxygen is reduced Oil, grease and paint can prevent corrosion (keeps oxygen and water out) A coat of tin can protect steel More reactive metals can prevent metals corroding

Answer 3

Nitrogen and hydrogen can react to make Ammonia N2 (g) + 3H2 (g) ⇌ 2NH3 (g) (+ heat) This reaction is at equilibrium Nitrogen can be obtained from the air (78% of the air is nitrogen) Hydrogen can be obtained from hydrocarbons (natural gas or crude oil) In industry, ammonia is made at a pressure of 200 atm and a temperature of 450°C in the presence of an iron catalyst (doesn't affect the position of equilibrium) Higher pressures allow the forward reaction to occur faster, so the highest possible pressure is used. The forward reaction is exothermic, which means that increasing the temperature will move the equilibrium the wrong way (away from ammonia and toward nitrogen and hydrogen), so the lowest temperatures are used that don't impact the rate of reaction too much. 450°C is the best compromise

Answer 4

Fertilisers can help plants grow. The three main essential elements are nitrogen, phosphorus and potassium - Fertilisers replace the missing elements in the soil to increase crop yield Ammonia can be neutralised with acids to produce fertilisers. Ammonia is a base and can be neutralised by acids to make ammonium salts. Nitric acid and ammonia form ammonium nitrate which is very good because it has a high percentage of nitrogen Ammonium sulfate and ammonium phosphate are also very good fertilisers Potassium nitrate is also a fertiliser - can be make by neutralising nitric acid with potassium hydroxide.

Answer 5

The burette is filled with sulfuric acid and the flask is filled with ammonia solution + methyl orange indicator Slowly add drops of sulfuric acid into the flask. Methyl orange is yellow in alkalis, but red in acids, so this colour change means that all the ammonia has been neutralised and ammonium sulfate has been made. However, the indicator is still in there so the solution isn't pure. To overcome this, you note how much acid was needed to neutralise the ammonia solution and repeat the experiment without the indicator. To get solid ammonium sulfate crystals, gently evaporate the solution until only a little bit is left, then leave it to crystallise. The crystals are then filtered out and dried, leaving you with a solid

Answer 6

The contact process is used to make sulfuric acid. The first stage is o make sulphur dioxide (SO2) - usually by burning sulphur in the air. S(s) + O2 (g) --> SO2 The sulphur dioxide is then oxidised (with the help of a catalyst) to make sulphur trioxide (SO3) 2SO2 + O2 ⇌ 2SO3 Next, the sulphur trioxide is used to make sulfuric acid SO3 + H20 --> H2SO4 Step 2 is a reversible reaction, so the conditions can be controlled to change the equilibrium position. Temperature - The reaction is exothermic, so to get maximum yield the temperature must be reduced, but not so much that the rate of reaction is slowed down. Similarly to the Haber process, 450*C is used Pressure - Increasing pressure is quite expensive, so it is normally kept at atmospheric pressure, or just above Catalyst - To increase the rate of reaction a vanadium pentoxide catalyst is used (V2O5)

Answer 7

This is pretty self explanatory so don't spend much time on it ``` When designing an industrial process, you should consider: Cost of raw materials Availability of raw materials Energy costs Rate Equilibrium position ```

Answer 8

``` This pretty much is about the environment costs of industrial processes You consider: - Materials and manufacture - Transport - Product use - Disposal ```

Answer 9

There are lots of different types of polymers, and each of them are useful for different things Ceramics are stiff but brittle. They are made by baking substances such as clay - Glass, porcelain, bone china etc Composites are made of different materials. One material (the reinforcement) is embedded in another (the matrix/binder) - Fibreglass, concrete, kevlar, etc. These tend to be expensive but very strong and light Polymers and metals are the other two, which i'm sure you know quite a bit about Ceramics are insulators of heat and electricity, and they don't degrade/corrode. They are also strong and hard wearing. Composites are very strong and are used to reinforce things Metals are good conductors of heat and electricity. They are malleable but corrode easily

Answer 10

Alkanes are saturated hydrocarbons. They are a homologous series of hydrocarbons - they contain only carbon and hydrogen atoms Their general formula is CnH2n + 2 - CH4 (methane), C2H6 (ethane), C3H8 (propane) etc They typically take part in combustion reactions C2H6 + 3.5O2 --> 2CO2 + 3H20 However, if there is a limited supply of oxygen then carbon monoxide is formed instead of carbon dioxide

Answer 11

Alkenes are unsaturated hydrocarbons; they have a carbon-carbon double bond. This means that the bond can open up, allowing the two carbon atoms to bond with other atoms. ``` They have the formula CnH2n I'm gonna try drawing them lol H H H H - C - C = C H H You can test for an alkene using bromine water. When added to bromine water, an alkene will decolourise the bromine water, turning it from orange to colourless. This is because the double bond can open up and form bonds with the bromine. ``` Alkenes can also be reacted with hydrogen in a process called hydrogenation. This forms an Alkane. If you are struggling to visualise this, message me on discord and i can send an image

Answer 12

Alcohols have an -OH functional group The general formula of an alcohol is CnH2n+1OH For example, ethanol is C2H5OH In certain situation this may be written as C2H6O, but that doesn't show the function -OH group, so refrain to doing this. Alcohols can be oxidised to form carboxylic acids. You need an oxidising agent, such as potassium manganate(VII)

Answer 13

Carboxylic are formed by oxidising alcohols. They have the general formula Cn-1H2n-1COOH and they have a -COOH functional gruop ``` Example: Methanoic acid: HCOOH Ethanoic Acid: CH3COOH Propanoic Acid: C2H5COOH ```

Answer 14

Addition polymers are made from unsaturated monomers, so alkenes for example. Ethene (C2H4) becomes polyethene (C2H4)n where n is how long the chain is. When writing out how the polymer looks, remember to remove the double bond present in the monomer and put brackets around it. (Ask me for an image if you don't understand) Naming these are quite easy - Just add the word poly before it (polypropene) Ask Musa for images of all of this

Answer 15

Condensation polymerisation usually involves two different types of monomer. Each functional group can react with the function group of another monomers, creating long chains of alternating monomers. For each new bond that forms, a small molecule (e.g. water) is lost Polyesters and Polyamides are examples of condensation polymers - Polyesters from when carboxylic acid monomers and alcohol monomers react together - Polyamides are formed from when carboxylic acid and amine monomers react (an amine monomer has nitrogen at the end) For all of this, ask me for an image

Answer 16

Crude oil is a mixture of lots of different hydrocarbons, mainly alkanes. The different compounds in crude oil are separated by fractional distillation. Oil is heated until most of it has turned into gas. The gases enter a fractionating column and the liquid bit is drained off at the bottom. In the column, there's a temperature gradient (it's hot at the bottom and gets gradually cooler) The longer hydrocarbons have high boiling points. They turn back into liquid and drain out of the column early on when they're near the bottom. The shorter hydrocarbons have lower boiling points so they turn into liquids much later on, near the top of the column where it's cooler. Each fraction will now have a different length of hydrocarbons, mostly alkanes

Answer 17

In crude oil, there are strong covalent bonds between the atoms within each hydrocarbon molecule. There are also intermolecular forces of attraction between different hydrocarbon molecules in the mixture When the crude oil is heated, the molecules are supplied with extra energy, making the move about more and eventually allow them to overcome the intermolecular forces that keep it with the other other molecules. The covalent bonds holding each molecule are a lot stronger, so they don't break. Intermolecular forces of attraction break a lot more easily in small molecules. That's why bigger molecules have higher boiling points.

Answer 18

Cracking is splitting up long-chain hydrocarbons Cracking turns long alkane molecules into smaller alkane and alkene molecules (which are more useful) It's a form of thermal decomposition, which is when one substance breaks down at least two new ones when you heat it. Like we said earlier, each atom has strong covalent bonds so a lot of heat is needed to break their bonds. A catalyst is often used to speed things up. We usually take the products of fractional distillation and crack them into smaller ones; the demand of something like petrol may be higher than bitumen. Cracking also produces alkene molecules Vaporised hydrocarbons are passed over powdered catalyst at about 400 - 700*C and 70 atm Aluminium oxide is the catalyst that is usually used

Answer 19

Fuel cells use fuel and oxygen to produce electrical energy A fuel cell is an electrical cell that's supplied with a fuel and oxygen and uses energy from the reaction between them to produce a potential different across the cell, until all the reactants have been used up. Hydrogen and oxygen react to produce water - this is an exothermic reaction. The hydrogen-oxygen fuel cell releases heat energy and nice clean water, so there's no pollutants Hydrogen-Oxygen Fuel cells involve a redox reaction. The electrolyte is often a solution of phosphoric acid. Hydrogen goes into the anode compartment and oxygen goes into the cathode compartment (Ask me for an image). In fuel cells, the anode is negative, which is the opposite of how it is in electrolysis At the negative electrode, hydrogen loses electrons to produce H+ ions. This is oxidation At the positive electrode, oxygen gains electrons from the electrode and reacts with H+ ions to make water. This is reduction. 2H2 + O2 --> 2H2O Fuel cells are quite complicated so just ask me for the image

Answer 20

Phase 1 - Volcanos gave out steam and CO2 Phase 2 - Green plants evolved and produced oxygen. Nitrogen gas was also put into the atmosphere by the ammonia reacting with oxygen and denitrifying bacteria Phase 3- Ozone layer formed, allowing evolution of complex animals. This layer blocked harmful rays from the sun. Our atmosphere is 78% nitrogen and 21% oxygen

Answer 21

Due to the increasing population of humans, more carbon dioxide was produced. CO2 is a greenhouse gas. The greenhouse effect helps to keep the earth warm Greenhouse gases are the gases in the atmosphere that can absorb and re-emit heat radiation. They're only present in small amounts. Carbon dioxide, water vapour and methane are all examples of this. If the concentration of greenhouse gases in the atmosphere increases, more heat radiation is absorbed in the earth and the atmosphere heats up, causing global warming

Answer 22

Ethanol can be produced from plant material, so it is known as biofuel. It's made by fermentation of plants and is used to power cars in some places. It's often mixed with petrol to make a better fuel. It's carbon neutral but farmers cant produce enough to keep up with demand Biodiesel is another biofuel. It can be produced from vegetable oils such as rapeseed oil and soybean oil. These are also carbon neutral, but we can't produce enough to replace diesel

Answer 23

Acid Rain - As fossil fuels are burned, harmful gases are produced, such as sulfur dioxide. This comes from the impurities in the fossil fuels. These can then mix with clouds, causing acid rain. Photochemical smog - A type of air pollution caused by sunlight acting on oxides of nitrogen. They produce ozone, which can cause breathing difficulties Carbon monoxide - As we know, this is a harmful gas as it can stop your blood from carrying oxygen around the body

Answer 24

Water is purified in water treatment plants. The three methods we can use are: 1) Filtration - A wire mesh screens out large twigs, and then gravel and sand beds filter out any other solid bits 2) Sedimentation - Iron sulfate or aluminium sulfate is added to the water, which makes fine particles clump together and settle at the bottom 3) Chlorination - Chlorine gas is bubbled through to kill harmful bacteria and other microbes