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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)
S4O62- In this redox titration, potassium iodide in the acidic medium acts as a reducing agent is added to the bleach solution to generate the iodine by the reduction of the hypochlorite ions. The formed iodine is then back-titrated with sodium thiosulphate to reduce iodine to iodide ions while sodium thiosulphate is being oxidized in order to determine the amount of hypochlorite ions originally present. When the brown colour of iodine fades as the end point approaches, a little amount of starch solution is added.
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If coloured or oxidized cations are present, the procedure will be more complicated. In this experiment, iron (II) ions in fact also participate in the redox reaction: Fe2+ � Fe3+ + e- Procedures 1) Plastic bag with iron (II) oxalate crystal was provided. 2) The weigh of the plastic bag with crystal was taken. 3) Iron (II) oxalate crystal inside the plastic bag was put into a beaker. 4) The weigh of the plastic bag without crystal was taken. 5) About 150 cm3 of 2M sulphuric acid was added to the beaker. 6)
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The gas syringes available are also too small, with a maximum capacity of 100 cm3 or 0.1 dm3. I will aim to collect a maximum of 80cm3 of gas, to allow some error before the maximum capacity of the gas syringe is reached. Due to the fact that the first reaction will produce a greater volume of gas, and the figure being taken into consideration is the maximum volume produced, the first reaction is what shall be used to calculate sensible quantities for the reactant.
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It is an irreversible reaction, meaning that it is impossible to reverse the reaction back to how it originally was. Hypothesis It is to be expected that it will be possible to identify each unknown cation and anion by various testing methods. Safety assessment Goggles Should be worn to prevent any spillages coming into contact with the eyes Lab coat Should be worn to prevent any spillages on clothes. Glass ware Correct procedures to be followed for cleaning up, if any breakages occur.
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Hypothesis It is expected, that it will be possible to purify contaminated water using ion exchange Safety assessment Goggles Prevents from any splashes getting in the eyes. Lab coats Prevents staining of clothes. Stools and bags Should be put away, preventing trips and falls. Pipettes Must be handled carefully, as the tip is fragile and can break Liquids Care must be taken when measuring and the correct procedures must be carried out when cleaning up any spillages. Sodium Hydroxide is an irritant, so hand washing is important. Copper Sulphate and Lead Nitrate is harmful, and Nitric Acid is corrosive.
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It has an electron shell of 2, 8, 18, and 1 - and is an excellent conductor of electricity. HYPOTHESIS It is to be expected that there will be a loss in weight at the end of the experiment. SAFTEY ASSESMENT Tying hair back Can catch alight with the Bunsen flame, and gets in the way of working. Goggles Must be worn, as liquids are being used. They protect the eyes from any splashes. Bunsen burner Ensure that the hole is closed, keeping a visible flame for when the Bunsen is not in use. Lab coats Worn to protect clothes Bags and stools Keep them both tucked under tables or moved out of the way for a clear fire exit, and to prevent falling over them, etc.
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The mobile phase is a developing liquid. The developing liquid (Butyl Ethanolate), travels up the stationary phase, moving the samples with it, in this case over the counter analgesics. The samples will separate on the stationary phase according to how much they absorb on the stationary phase against how much they dissolve in the mobile phase. Hypothesis It is to be expected that substance x will be able to be identified using thin layer chromatography. Safety assessment Goggles Prevents from any splashes getting in the eyes. Lab coats Prevents staining of clothes.
- Word count: 937
Load/ g Extension /mm 0g 0mm 50g 95mm 100g 130mm 150g 160mm 200g 190mm 250g 220mm 300g 250mm 350g 280mm 400g 310mm D4 Applying hook's law, by using my theoretical knowledge I predict that the extension of the spring will be directly proportional to the mass added length. In order to increase the accuracy of the result, first I have found more precise values of mass using the following formula mass/g, instead of just assuming each gram, and then I used a couple of equipment such as stand, spring, mass and a ruler marked with a millimetre scale for greater
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The rust forms away from the surface of the iron, as the iron and hydroxyl ions diffuse away. Iron has a more negative electrode potential than oxygen + water (-0.44V compared to +0.40V), which explains why it gives away electrons (oxidation) instead of accepting them (reduction). By coating the iron in a substance with a more negative electrode potential, the coating will give up electrons more readily than the iron. Therefore the coating will be oxidised and the iron will be protected. Ferroxyl indicator is a mixture of Phenolphthalein in sodium chloride solution, and potassium hexacyanoferrate(III). It turns from orangey-yellow to pink in the presence of hydroxyl ions, and to a blue colour in the presence of Fe3+ ions (the charge of the iron ions in the iron(III)
- Word count: 1245
Fission does not happen spontaneously; it requires a trigger. An unstable nucleus bombarded with a neutron will "elongate and divide itself like a liquid drop"  as its surface tension is decreased due to its charge . Reaction 1 - a possible fission reaction of uranium Source  100 words Explain the role of hydrogen nuclei and helium nuclei in the synthesis of elements in stars. Give a detailed explanation of the nuclear changes that happen when lithium forms in stars.
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The end-point of the titration is detected by the first persisting pale pink colour change from purple. Even at the end-point the pink colour will fade after a short period as the MnO4- ions react with Mn2+ ions. As the chlorine solution is of concentration approximately 7g dm-3 it is possible to calculate quantities and concentration of other reactants so the experiment will give realistic outcomes. For instance if the concentration of MnO4- is too low in the titration with the Fe2+ then the volume used will be large, possibly requiring more than one burette volume. This introduces unnecessary inaccuracies, of having to repeat the set-up of the burette and also increases the time for the experiment.
- Word count: 1340
The overall titration reaction of the zinc tetraamine complex and the form of predominate EDTA (HY3-) at pH of 10 is summarized below: Zn(NH3)42+ + HY3- ? ZnY2- + NH4+ + 3NH3 The proton exchange triggers the black T indicator to change colors from purple to blue sharply at the endpoint, and the molar concentration of EDTA can be calculated using the molar ratio and volume of EDTA added to achieve the color change. Experimental Procedure Preparation of 0.01 M EDTA Solid disodium ethylenediaminetetraacetate dehydrate (EDTA)
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METHOD 2 Table of results 1st Titration 2nd Titration 3rd Titration Initial burette reading (cm3) 0.00 37.80 75.50 Final burette reading (cm3) 37.80 75.50 113.40 Titre (cm3) 37.80V 37.70V 37.90V Average titre (cm3) 37.80 + 37.70 + 37.90 3 = 37.80 Treatment of results The equation for the neutralisation reaction in my titration is shown below. LiOH(aq) + HCl(aq)
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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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(*In the experiment, we have only got one thermometer so we measured the temperature of the water bath.) 6. After both of the solutions reach the suitable temperature, they are poured into the beaker which is prepared in step 3. Start the stop watch simultaneously. 7. The solution is stirred*. A person watches the cross vertically during the reaction. (*In the experiment, we did not stir the solution.) 8. Stop the stop-watch when the cross on the paper just 'disappeared'.
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There's 100cm� of LiOH, so it will be: 0.003485 � 4 = 0.01394 Moles present in 100cm� of LiOH 0.0139 moles Relative atomic mass of Lithium R.A.M mass / moles 0.12 / 0.0139 8.633093525 R.A.M of Li 8.633 HAZARD OF CHEMICALS IN THIS EXPERIMENT Care must be taking when handling chemicals in this experiment. Safety goggles and lab coat must be worn at all times. Ensure room is well ventilated. Li: Flammable, burns in air, react violently with water and oxygen.
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& pressure (1atm), 1 mole of gas = 24000cm3 So if the equation 1 is correct, then volume of gas given off = 0.0037 � 24000 = 89cm3 Equation 2: Ratio of - CuCO3 : CO2 1 : 1 Mass of 1 mole of CuCO3 = 123.5g Mass of Copper Carbonate used = 0.4g Moles of CuCO3 = 0.4 � 123.5 = 0.003 moles As the ratio is 1:1, so moles of gas given off = 0.003 moles At room temperature (20�c)
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of moles of NaOH used in titration = 8.25 x 10-3 moles * No. of moles of HCl reacting with NH3: 0.015 - 8.25 x10-3 = 6.75 x 10-3 mole * By the equation NH3 + HCl --> NH4Cl, Number of moles of NH3 in the sample of salt = no. of moles of HCl = 6.75 x 10-3 mole * Molar mass of NH3 : 14 + 1 x 3 = 17 g/mole * The mass of NH3 in the sample = 17 x 6.75 x 10-3 = 0.11475 g * % by mass of NH3 in the sample = 0.11475 / 0.425 x 100% = 27.0% B.
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The benzoic acid was dissolved with minimum amount of boiling water, and the solution was allowed to cool down to initiate the formation of the crystals. 8. The crystals were obtained by suction filtration and were dried in an oven for 1 night. 9. The dried crystals were weighed and its melting point range was determined. Data and Calculation 1. The gas evolved in step 4: NH3 Test: the steam was directed to a piece of pH paper to measure the pH.
- Word count: 850
Relevant Equations/Chemical Reactions Involved : (1) Reaction between propanone and iodine : (2) Reaction between iodine and thiosulphate(VI) ion (titration) : I2(aq) + 2S2O32-(aq) � S4O62-(aq) + 2I-(aq) 7. Chemicals : 0.02 M iodine solution (Iodine dissolved in potassium iodide solution) 1 M propanone solution 1 M sulphuric acid 0.5 M sodium hydrogencarbonate solution 0.01 M sodium thiosulphate(VI) solution Starch solution 8. Apparatus and equipment : 10.0 cm3 pipette 1 Burette 1 25 cm3 measuring cylinder 1 Filter funnel 1 10 cm3 measuring cylinder 1 White tile 1 100 cm3 Beaker 2 Stop watch 1 250 cm3 Conical flask 4 Pipette filler 1 Safety spectacle 1 Wash bottle 1 9.
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I would be using phenolphthalein as my indicator, because the phenolphthalein will change colour just before the equivalence point and therefore, too much acid will not be added to the solution. This means it will be much more accurate than something like Methyl Orange, which would change after the equivalence point and after too acid much has been added.iv To carry out the titration I also need to know the balanced chemical equation for the reaction.i Balanced Equation for the Reaction Ca(OH)2 (aq)
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Trial 1 2 Final volume of Sulphuric acid, cm3 47.60 40.40 43.10 Initial volume of Sulphuric acid, cm3 21.40 15.40 18.20 Volume used, cm3 26.20 25.00 24.90 Mean volume used, cm3 24.95 Molarity of NaOH in 25cm3 of NaOH solution 0.05M*24.95cm3*2 *10*1/1000*1/0.025dm3 =1.00M(cor. to 0.01M) 2. Hydrolysis of aspirn An aspirn tablet was placed into a 250 cm3 conical flask. 25 cm3 of the standardized 1M NaOH was pipetted into the conical flask and about same volume of deionized water was added into it.
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This causes solid to change to a liquid form or state. The temperature remains constant as the phase changes. As more energy is increased or heat is delivered to the particles it causes the liquid to change its shape to gas. This is known as the process of phase change. When you are going from liquid to solid, the energy of the particles decreases and there is less movement within the particles. Finally, in this lab the phase changes from solid to liquid will be observed.
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The equation :(MEBT)- + NaH2EDTA � (MEDTA)-2 + 2 HEBT2-+ H+ + 2Na+ red-wine blue Consequently, the end-point changes from red-wine colour to blue colour. Objective To determine the total hardness in a sample of water by the EDTA titrimetric method Procedure Please refer to the lab manual Result Standardization of EDTA Solution Trail 1 2 3 Initial Reading(ml) 1.50 0.00 0.00 Final Reading(ml) 40.20 39.40 39.10 Volume of EDTA used (ml) 38.70 39.40 39.10 Average volume of EDTA used = (38.70+39.40+39.10)
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The hydrochloric solution will be diluted 10 times to reduce the concentration from 0.3moldm-3 to 0.03moldm-3. This new concentration will therefore be twice the concentration of the calcium hydroxide. Diluting hydrochloric acid 1. Firstly I will ensure the pipette has been washed with distilled water and then washed with hydrochloric acid. This will make sure that all traces of previous solutions have been removed. 2. Then I will fill the pipette with hydrochloric acid using the pipette pump. When the pipette has been filled pass the 25cm-3 line, I will allow the pipette to empty.
- Word count: 2135