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AS and A Level: Inorganic Chemistry
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Top tips for writing reactions
- 1 Remember to balance the charges on any ionic compounds. The common ions are NO3-, SO42-, OH- and CO32-.
- 2 Do not forget to put state symbols on all of your balanced reactions.
- 3 Each side of the reaction must have the same number of atoms on it. Think about a balanced seesaw.
- 4 Your three main acids that you will use have the formulae HNO3 (nitric acid), H2SO4 (sulphuric acid) and HCl (hydrochloric acid).
- 5 Remember that all metal hydroxides and metal oxides are bases. This will help you when using word equations to figure out your products.
Five common mistakes students make when studying inorganic chemistry
- 1 When observing a gas being produced, you would not write “I saw a gas” as most gases are invisible. Instead you should write “I saw bubbling / fizzing / effervescence”.
- 2 When asked to write a word equation, students often write a symbol equation and vice versa. This will get you no marks in the exam.
- 3 - When asked for “standard conditions” people often say “room temperature”. This is not sufficient. You must say 25 degrees celsius (298K). Other standard conditions you must know are 1 atmosphere of pressure and concentrations of 1 mol dm-.
- 4 If you are asked to state a colour change you must state the initial and final colour.
- 5 Students often give group 2 metals a 1+ charge. Remember that all group two metals (Be, Mg, Ca, St, Ba, Ra) have a 2+ charge.
Five word equations that you must know
- 1 Acid + base / alkali = salt + water (eg HCl + NaOH becomes NaCl + H2O)
- 2 Metal carbonate = metal oxide + carbon dioxide (eg CaCO3 becomes CaO + CO2)
- 3 Metal + oxygen = metal oxide (2Mg + O2 becomes 2MgO)
- 4 Metal + water = metal hydroxide + hydrogen (eg 2Na + 2H2O becomes 2NaOH + H2)
- 5 Metal oxide + water = metal hydroxide (eg CaO + H2O becomes Ca(OH)2)
- Marked by Teachers essays 2
- Peer Reviewed essays 9
Therefore, this concentration of acid has not got any risk. However, we will still be taking precautions in order to avoid any possible harm. We will use goggles to avoid acid contact with the eyes and gloves to avoid direct contact with the hands when using it. Also, if the acid is spilt on skin or clothes we will rinse it with water and then wipe it using a dry cloth.4 If it spills either on the floor or on the table, we will clean it up using a damp cloth with water.
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I can read the burette to the nearest 0.05cm3 so the precision error is �0.025cm3 for each reading. I will have to read the burette at the beginning and end of the titre so the precision error for each titre is �0.05cm3. If the titre is 30cm3 the error is (0.05/30.00) x 100 = 0.16% which is acceptably low. A pipette 7 I will need a very accurate, glass pipette which I can use to transfer a specific known volume of sulfuric acid added to the conical flask to be reacted.
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Therefore the best volume of solution to use per titration will be 25cm3, as it allows the acid to have a concentration greater than or less than the assumed 0.1 mol dm-3. To produce reliable results, I will need to complete three titrations with a range of no more than 0.1cm3. Taking into account a rough titration and any anomalous results, I will probably need to do at least six titrations, which will require 150cm3 of sodium carbonate solution. The solution will be made up in a volumetric flask, which has set volumes.
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It is often shortened to RMM. The RMM is used in many sorts of calculations in chemist. And for calculating this I will need to know the relative atomic mass of a substance. This is can be found by using the periodic table. So here I will work out the molecular mass of anhydrous sodium carbonate: Na2 - 23.0 (atomic mass) x 2 (atoms) = 46 C - 12 (atomic mass) = 12 O3 - 16 (atomic mass) x 3 (mass)
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You will also notice that Endothermic reactions have a much greater Activation energy than Exothermic reactions and this is because the energy taken to form new bonds is greater than the energy taken to break them. The rate of a reaction is the time taken for the particles to reach the activation energy and for the reaction to 'go'. The fewer the number of particles with the activation energy, the slower the rate of reaction, and vice-versa. Not every particle in a substance can have the minimum energy requirement for the reaction and this is when outside factors can affect the rate of the reaction.
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Single bonds are relatively easy to break as opposed to double or triple bonds. Endothermic and Exothermic Reactions: Exothermic reactions are those that give energy into their surroundings in the form of heat, heating the surroundings. This allows us to heat up the water directly above the spirit burner. An endothermic reaction is totally opposite to an exothermic reaction as endothermic reactions take in energy from the surroundings and cool the surroundings. Here are some bond energy diagrams for exothermic and endothermic reactions: This shows the negative enthalpy change as energy is given to the surroundings.
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All chemicals have different rates of reaction. The rate of a chemical reaction can be changed if (2): - The pressure of the gas is changed Increase in pressure means that the molecules (mainly in gases) have less space to move around in so have a greater chance to collide with other molecules and react. - The temperature of the reactants is increased Increasing the temperature of the system will increase the chances of successful collision because the molecules will have more kinetic energy and will collide with other molecules with more power increasing the chance of a reaction.
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However steel reinforcing that is constantly exposed to aggressive corroding chemicals such as seawater (Chlorides) often requires an extra level of protection beyond what the concrete alone can provide. The most common method used to protect against corrosion is an epoxy coating on the steel. Other methods used include switching to Galvanised and stainless steel reinforcement, either Impressed Current or Galvanic cathodic protection systems, and chemical and mineral corrosion protection systems. This report will be investigating two corrosion protection systems, epoxy coating and impressed current cathodic protection, analysing their advantages and disadvantages in order to determine which method is the most effective to protect against corrosion in steel reinforcement in concrete coastal structures.
- Word count: 3006