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GCSE: Aqueous Chemistry
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The rates of aqueous reactions
- 1 The rate of reaction can be increased by increasing the concentration of the solution. This will mean there are more molecules in the same amount of space, so there will be more collisions.
- 2 The rate of reaction can be increased by increasing the temperature of the solution. This will give the molecules more energy, making them move faster and collide more. It will also mean they stand a better chance of having the activation energy.
- 3 The rate of reaction can be increased by increasing the pressure of the solution. This will mean there are more molecules in the same amount of space, so there will be more collisions.
- 4 Adding a catalyst to the solution will increase the rate of reaction. This is because the catalyst lowers the activation energy needed for the solution to react.
The definition for rate of reaction is “change in concentration of product or reactant over time”.
It has the units mol dm-3 s-1
How to calculate the number of moles in a solution
The two most important equations to learn are:
moles = mass / Mr and moles = volume x concentration
If you know the moles of one chemical in your balanced equation, you can find out the moles of anything else by looking at the “big number” ratios. For example:
2NaOH + H2SO4 = Na2SO4 + 2H2O
If you had 10 moles of H2SO4, because there is a 2:1 ratio, you would have 20 moles of NaOH.
- 3 Your volume MUST be converted into dm3 before you use it in your equation. To convert cm3 into dm3 divide your number by 1000.
- 4 Do not forget to round your answer to a sensible number of significant figures (usually the least amount of significant figures that the question itself goes to).
- 5 Your Mr can be found by looking at the mass number on the periodic table (this is the bigger of the two numbers- the smaller one is called the proton number
Top tips for aqueous reactions
- 1 Anything that is dissolved in an aqueous solution will have the state symbols (aq). For Na+(aq)
- 2 If your reaction is dissolved in water, then water will have the state symbol (l), for “liquid”.
- 3 If the question says that your reaction is done under standard conditions, then it means at 1 atmosphere of pressure, at 25'C.
- 4 When constructing balanced reactions, do not forget to balance your charges when making salts. For example: HCl + Mg = MgCl + 0.5H2 would be wrong. The correct answer would be 2HCl + Mg = MgCl2 + H2.
- 5 The most important equation reaction to remember is acid + base = salt + water. This crops up all of the time in exams!
There are four major factors that affect the speed of a reaction; Temperature, Concentration, Catalyst and Pressure/Concentration. In this experiment, the effect that a Concentration has on the speed of a reaction will be tested. This means, however, that the other variables will have to remain unaltered throughout all the tests. If they were to vary, the tests could not be considered reliable. I will make sure the temperature does not vary by checking that the room is at room temperature. I will not use catalysts, and make sure that all equipment is not contaminated by any other chemicals. I will use the same equipment in each experiment to make sure that the pressure/concentration does not vary.
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Method: *Pour water into basin. *Fill measuring cylinder with water. *Place the measuring cylinder upside down into the basin making sure that the cylinder if full of water when upside down. *Place a gas pipe into the measuring cylinder and put 3g of calcium carbonate chips and 15ml of hydrochloric acid with any amount of molar into the gas pipe. *Time the experiment measuring the amount of carbon dioxide displacing the water every 10 seconds until the water is displaced.
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Science Investigation Report - Aim To investigate how the voltage of the electric current would affect the rate at which a metal is electroplated.
This then leads to another formula: V = IR (Voltage = Current x Resistance) One can deduce that if the resistance of the circuit stays the same, the voltage of the electric current would be the only factor affecting the current. This would mean that when the voltage of the electric power supply increases, the electric current would also increase proportionately. As the current increases, the charge of the electricity would also increase, causing meaning that the flow of electrons in the circuit would also be faster. If the flow of the electrons is faster, it would mean that the rate of electroplating would also increase within a fixed amount of time.
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A thermometric titration - determine the concentrations of hydrochloric acid and ethanoic acids by thermometric titration and find the enthalpy of neutralization.
(II) Titration of CH3COOH with standard NaOH: 1. The procedure was the same as HCL except CH3COOH was used. Results and Calculations: (I) Titration of HCL Volume Added/ cm3 1.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 Temp /oC 25.0 27.5 28.5 30.0 30.5 31.0 30.0 29.0 28.5 27.5 22.5 (II) Titration of CH3COOH Volume Added/ cm3 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 Temp /oC 23.0 24.5 24.5 24.5 24.5 24.5 24.5 24.5 24.5 24.0 24.0 Calculations: 3. Concentration of HCl: (1)(50)
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The answer was 8.33 ml. DATA- Standardization of NaOH Solution Sample 1 Sample 2 Sample 3 Mass of KHP .335 g .320 g .307 g Initial Volume NaOH, Vi(mL) 0 mL 17.2 mL 27.3 mL Final Volume NaOH, Vf (mL) 17.2 mL 34.6 mL 43.4 mL Total Volume NaOH used (mL) 17.2 mL 17.4 ml 16.1 mL Moles KHP .0016 mL .0016 mL .0015 mL Moles NaOH .0016 mol .0016 mol .0015 mol Molarity NaOH .093 M .092 M .093 M Average Molarity .093 M - - Standardization of HCL Solution Sample 1 Sample 2 Sample 3 Volume of HCL
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This method is extremely precise but is a lot more expensive and a lot harder work. A Colorimeter typically retails at around �800 and they also need to be calibrated and adjusted before the experiment, the colour also need to be measured every few seconds, and the results can only be interpreted in graphs. Collision Theory- What is Reaction Rate? Reaction Rate is defined as how fast a reaction takes place. It is a measure of how fast a Chemical Reaction occurs.
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mass is 391.90 We can calculate the number of moles by using the following formula Number of moles = concentration x volume So 0.05 X 0.025(this has to be converted dm3) = 0.0125 APPARATUS: * Volumetric flask * 10 cm pipette * 100 cm conical flask * burette * distilled water *
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To detect the contaminant polluting the water Barium Nitrate To detect the contaminant polluting the water Sodium Hydroxide To detect the contaminant polluting the water Silver Nitrate To detect the contaminant polluting the water Test Tube To allow the contaminated water be tested in Flame Test Wire To test for contaminant over flame Bunsen Burner To provide flame for experiment Contaminated Water To test for various contaminants contained within Method Method A I have been given a sample of contaminated water.
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Investigation of aqueous electrolytic cells.For this experiment, we are to test an aqueous solution, choosing from the four selections given: sodium chloride, copper sulfate, copper chloride and hydrogen sulfuric acid.
Hypothesis (including reason): If the voltage increases, the amount of solid discharged from the electrode will increase as well. I predict that the solid discharged from the electrode will increase as the voltage increase in the circuit because as the voltage goes higher, the more energy will be produced and the faster the solid will be discharged from the electrode. And hence, the mass of the electrode will gradually become heavier as the voltage increases. Variables: Independent variable: voltage For the independent variable, it is the voltage, because I have to change it as we finish the experiment every time, meaning the input of the experiment.
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Mix 40 grams of NaOH into 1000 ml of water. This 1M solution of NaOH is to be used for the remainder of the procedure in place of NaOH. 2. Label the beakers with the tape and permanent marker. Then, fill the beakers. Label one beaker "room temperature" and fill it with 200 ml of water. Label the second beaker "hot", then fill it with 200 ml of water and place it on the stove top. Label the third beaker "cold", then fill it with water and ice up to the 200 ml mark accounting for displacement.
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With every drop that falls into the beaker, there will be a 'pink splash' and then it will disappear. Keep swirling the beaker for thorough mixing. 6. Carefully observe the drops falling because when the drop of sodium hydroxide does not create a pink splash that is when the neutralization has happened. Or when the solution suddenly turns pink, it can be assumed that alkali just became surpassed the amount needed to neutralize the acid and one drop before was when neutralization was complete.
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10) Work out the mean result. 11) Repeat steps (1) - (9) but change your material each time. Preliminary Results (1) All results to 2 decimal places (2.d.p) In this preliminary, I used three different balls which two of them were roughly the same size and weight except for the lead, even though it was about the same size, it was about 1000g heaver than the brass and copper. I dropped it in the same viscous liquid to test how long it took for them to drop to the bottom of the measuring cylinder. It has shown that on average the lead ball dropped to the bottom the fastest with the average speed of 48.64 seconds.
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Rub sand paper on both the electrodes, wash with de-ionised water, ethanol and finally propane and then let them dry. 2. Then weigh the electrodes, handling them carefully to prevent them from becoming greasy. Record your readings. 3. Take copper (II) sulphate solution in a beaker and place the electrodes in it. 4. Set up the following circuit: 5. Switch the circuit on and quickly adjust the variable resistor on the power pack so that the ammeter displays a reading of 0.10 amp. 6. Allow the current to flow for a measured period of time. Maintain the constant current. 7.
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similar to a battery and produces electricity while the reactants are supplied continuously from an external source. Fuel is fed continuously to the anode while the cathode is being feeding the oxidant. The electrolyte layer that acts as a doorway allows ions to pass through however no electrons because they are being forced into the external circuit creating a chemical reaction. One important factor about the hydrogen fuel cells is that it will continue to supply fuel until the fuel (hydrogen being an unlimited resource) has finished. Hydrogen fuel cells do not require electrical recharging and can generate power almost indefinitely as well.
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2.2 Modifications: * Lab manual stated that only "plastic" lab ware be used in the experiment, but instead, glass was used during the laboratory experiment and not all plastic. * The sample of magnesium salts were not transferred with washings. 3. Experimental Results: 3.1 Determination of Magnesium Using an EDTA Titration.
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Experimental Results: 3.1 Data Table CLASS DATA Raw Data - Concentration Data Reaction Time Avg time (s) Reaction mL H2O2 ml I- Run A Run B Run C 1 5 5 839 1300 1245 1128 2 7.5 5 379 594 796 590 3 10 5 632 447 764 614 4 12.5
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Materials and Apparatus: * Burette * 25cm� pipette * Retort stand * Clamp * Conical flask * Pipette filler * Phenolphthalein * Sulphuric acid * 25cm� of 0.1 ml/dm� Sodium hydroxide Procedure: 1. Wash all equipment 3 times with distilled water 2. Rinse the burette with a little of the acid and then fill it up 3.
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Barium Chloride * Silver Nitrate * Potassium Thiocyanate * Dilute Nitric Acid * Iron (II) Iron (II) Sulfate Sodium Hydroxide Color change to mossy green. Precipitate is heavy and gathers at the bottom. Barium Chloride * Silver Nitrate * Potassium Thiocyanate * Dilute Nitric Acid * Iron (III) Iron (III) Chloride Sodium Hydroxide Color change to orange. Precipitate is formed. Barium Chloride * Silver Nitrate * Dilute Nitric Acid * Potassium Thiocyanate * Iron (III) Iron (III) Chloride Potassium Thiocyanate Color change to bloody red.
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These bond with the hydrogen ions and become hydrogen atoms. These atoms bond in pair to form molecules which effervesce and escape as gas. Rates of Reaction There are three factors that influence the speed of which magnesium reacts with sulphuric acid. I will look at each of these in detail. * The concentration of sulphuric acid. If the concentration of sulphuric acid is increased then the speed of the reaction will be increased. This is because with an increase in concentration then there will be more hydrogen ions present.
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Record your result in Table 2. Note that mixing of coloured solutions can give another coloured solution. Furthermore, apart from the vanadium ions, other coloured products may be also be formed. (If you suspect iodine to be produced, test by adding about 3cm3 of 0.2M sodium thiosulphate solution into test tube.) 6. Data Treatment No. of mole of ammonium metavanadate = 2.5x10-3 mol Mass of ammonium metavandate = 2.5x10-3x (14+4+50.9+16x3) = 0.29225g Mass of ammonium metavandate used = 0.29g Table 1 Chemical mixed Observation NH4VO3+ H2SO4 The color of mixture turns to pale yellow.
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The enthalpy change of an endothermic reaction must be larger than zero. The enthalpy change of an exothermic reaction must be smaller than zero. Procedure : Apparatus needed : safety spectacles, a pipette with 25 cm3, a pipette filler, a polystyrene cup with lid, a weighing bottle, a spatula, a thermometer which is started form 0 oC to 100 oC with 0.1 oC graduations, a watch, a balance, a beaker 1. The pipette was washed with pipe water, and then distilled water was used to clean the pipette. Finally, it was cleaned with the solution which would be used later.
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There are many ways ammonia could be used e.g. Ammonia could then be used to make nitric acid, which reacts with ammonia to create ammonium nitrate, which is a fertilizer. The raw materials for creating ammonia are nitrogen (N2 (g)) from the air and methane and water for hydrogen (H2(g)). Hydrogen is process by taking methane (CH4 (g)) and reacting it with steam (H2O (g)) and creating carbon dioxide (CO2(g)) and hydrogen (H2(g)). Therefore in this production the high temperatures favour the reverse reaction. According to the le chateliers principle, the lower temperature is favored.
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Competition reactions in aqueous solutions * In displacement reaction, a more reactive metal will displace a less reactive metal from a solution of its salt. c. Identifying metal ions * When an alkali dissolves in water, it produces hydroxide ions. * Most metal hydroxides are insoluble.. * If hydroxide ions from a solution of an alkali are added to a solution of an metal salt, an insoluble often colored metal hydroxide is precipitated from solution. * In some cases the precipitate dissolves in excess hydroxide, owing to the amphoteric nature of the metal hydroxide.
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tensile strength - required for large bridges Manufacture of Na2CO3 - the Solvay process Used to manufacture soaps, detergents, dyes, drugs Na2CO3 = CaCO3 + NaCl + CO2 + NH3 in a Solvay tower, the centre of reactions CO2 and NH3 are recycled continuously Indirect uses of limestone Lime manufacture When CaCO3 is heated, it breaks up reversibly to form CaO and CO2. CaCO3 - CaO + CO2 .Thus reaction can go in either direction, depending on the temp and the pressure and takes place in a lime kiln.
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Precipitation. The purpose of this experiment is to become familiar with precipitation reactions. According to the textbook, precipitation is the process where a chemical reaction leads to the formation of a solid, which is called a precipitate.
Methods and Materials This experiment required the mixture of several different substances, followed by observation of the results. To perform these tests, a microtiter plate was used to contain the individual drops of substances. The substances provided included the following solutes: sulfuric acid, hydrochloric acid, silver nitrate, sodium carbonate, sodium chloride, potassium chromate, lead acetate, sodium sulfate, and barium chloride. Using pipets, these solutes were carefully mixed on the microtiter plate, which was used as a reaction chamber. Carefully, the reagents were dispersed and mixed, while the reactions observed and recorded. To discover the results of the reactions, it was necessary to use solubility rules to predict the reactions.
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