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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!
- Marked by Teachers essays 36
- Peer Reviewed essays 19
Biology Practical Investigation to find the lowest concentration of Copper Sulphate solution that will denature egg albumen.5 star(s)
The third bond is the hydrogen bond, which occurs between hydrogen and oxygen atoms within the polypeptide chain. Hydrogen bonds are not strong on their own, although a large number of them together makes them very strong. The primary structure is the linear sequence of amino acids stablised by peptide bonds. There are an endless number of different possible primary structure The secondary structure is the sequence of amino acids arranged as either an alpha helix of a beta pleated sheet stabilised by peptide s.
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Back Titration Lab Report. In my experiment, I hoped to find the amount of calcium carbonate in some mineral limestone using the back titration method4 star(s)
250 cm3 volumetric flask (� 0.2 cm3) 50.0 cm3 burette (� 0.05 cm3) 25. 0 cm3 pipette (� 0.1 cm3) 3 x conical flasks Clamp and retort stand 1.0 mol dm-3 hydrochloric acid, HCL 1.5 g of limestone phenolphthalein indicator 0.1 mol dm-3 Sodium hydroxide, NaOH Method: When I had all this, I started my investigation by weighing 1.5 g of limestone on the electric balance. After obtaining the weighed crystals I dissolved them with 1.0 mol dm-3 hydrochloric acid, in the beaker provided and stirred the mixture till bubbling stopped.
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If there were more hydroxide ions than hydrogen ions then once every hydrogen ion joined with 1 hydroxide ion there would be hydroxide ions left meaning the solution would become alkaline. When an acid contains more hydrogen then there are a greater number of hydrogen ions per ml than in an acid containing less hydrogen so it will be stronger. For example in sulphuric acid (H2SO4) there would be more hydrogen ions than in the same amount of hydrochloric acid (HCl), twice as many because there are twice as many in the formula.
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The aim of the experiments was to test food samples to see which food group the sample belongs to. I also did tests to determine what type of carbohydrate an unknown carbohydrate was.4 star(s)
* Pipettes Benedict's Test for non-reducing sugars * Benedict's reagent * Non-reducing sugar sample e.g. sucrose * Test tubes * Water bath or heating apparatus * Pipettes * Hydrochloric Acid * Alkali powder (sodium hydrogen carbonate) Starch Test * Starch Sample * Iodine * Tray * Pipette Emulsion Test * Ethanol * Lipid Sample * Water * Test Tubes Methods The Biuret test 1. Put about 2cm3 of the test sample into a test tube 2. Put an roughly equal amount of biuret's reagent into the same test tube using a pipette 3.
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Scientific Knowledge Salts contain positive and negative ions, which are held together by the strong force of attraction between particles with opposite charges. When one of these solids dissolves in water, the ions that form the solid are released into solution, where they become associated with the polar solvent molecules. H2O NaCl(s) Na+(aq) + Cl-(aq) We can generally assume that salts dissociate into their ions when they dissolve in water. Ionic compounds dissolve in water if the energy given off when the ions interact with water molecules compensates for the energy needed to break the ionic bonds in the solid and the energy required to separate the water molecules so that the ions can be inserted into solution.
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be neutral; the baking soda solutions will be acidic; the "green" cleaner will be basic; the household cleaner will be acidic; the Lemon Juice will be acidic. Materials: For this lab we need pH paper, a spot plate, water (distilled, if available), and substances with varying pH. Safety: In this lab we must were goggles and aprons to avoid skin contact with all chemicals that are going to be used in this experiment.
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What are the possible applications of the heat of neutralisation? 4) What are the possible ways to reduce the heat of neutralization in case a patient taking antacids is sensitive to heat? 5) Does the heat of neutralisation depend on the type of Acid Base combination? 6) Does the heat of neutralisation depend on the temperature of the surroundings? 7) How would the physical states of the reactants affect the heat of neutralisation? 8) How would miscible impurities affect the heat of neutralisation?
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As the H+ ions from the acid diffuse in the indicator within the agar will become colourless. The acid I will be given will be 1M Hydrochloric Acid (HCl). I will be given one Petri dish of pre-prepared pink agar poured to an approximate depth of 1cm. Safety It is important to remember safety whenever working in a laboratory particularly when handling corrosive solutions such as acids and bases. To this extent it is essential to always where safety goggles when doing any experiment. In order to ensure the safety of myself, and my friends I am going to take the following safety precautions during my experiment: * Ensure safety goggles are worn at all times during the experiment.
- Word count: 679
Investigate the rate of reaction between different concentrations of hydrochloric acid with metal carbonates using calcium carbonate as the example.
The calcium carbonate that is used will be in granules because: > They have a smaller surface area than powder, making the timing much easier. > They are easier to measure, which will help the accuracy of the experiment. Preliminary Work During my preliminary work I tested the highest and the lowest and highest concentrations, I did this to find the shortest and longest times it would take to do the experiment. The results obtained are shown below: Calcium Carbonate Granules (g)
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The concentrations will be changed by using different measurements of hydrochloric acid and water. Controlled Variable The equation for the reaction can be seen below; Mg(s) + 2HCl(aq) --> MgCl2(aq) + H2(g) I will be controlling many of the variable which affect the volume of hydrogen which is produced. Temperature - The temperature will be controlled because if the temperature was to be changed this could affect the dependent variable. To control this the experiment shall be done in the same lab with no heating and no cooling will be done while the temperature will also be maintained using a thermometer.
- Word count: 841
The gas is produced by 4 marble chips been put in the acid which produces gas. Hydrochloric acid + calcium carbonate --> calcium chloride+ carbon dioxide. Sceintific knowledge that will help with my prediction: > When a reaction occurs the particles of two reations must collide. > A much more conentrated solution has more particles per cm /ml. > So, if there are more particles in both solutions and solid the particles will be able to collide more easily and so, making the reaction quicker. > The particles must have a lot more energy so that they move fast and when they collide with each other they don't just brush past each other.
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acid present. 4. A few anti-bumping granules were added to the flask, and it was attached to a water-cooled reflux condenser. It was refluxed for 1 hour. The flask and its contents in an ice bath was cooled. 1.0 cm3 sample was removed from the flask for titration with the 0.50 M sodium hydroxide solution as before. The titre needed was recorded (V3)and was corrected for the sulphuric(VI) acid. 5. Refluxing was continued for an additional half hour, and was then cooled and was titrated another 1.0 cm3 sample.
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Oserving the properties of water. Place a drop of water on a smooth plastic sheet or on the bench. Look at it closely from the side.4 star(s)
Experiment #2: Fill a clean 250 ml. beaker with water to about 1 cm. below the top. Carefully float a small filter paper on the surface. Carefully drop a needle, exactly horizontal, on the paper. Wait until the paper becomes soaked and sinks. Observe the needle carefully. After you have observed it, add one drop of detergent with a glass or plastic rod. * the piece of paper floats on the water and then it sinks because it get too wet.
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Heat the contents of the crucible gently at first and then strongly. 4. Remove the crucible from the burner when all the water of crystallization is removed from the copper sulphate crystals. 5. Allow the contents of the crucible to cool down. 6. Weigh out the crucible with its contents again until a constant reading is obtained. Table of Results Substance to be Weighed Weight in Grams Beaker alone 50.00g Beaker + copper sulphate before heating 52.50g Beaker + copper sulphate after heating 51.44g Observation: * The beaker was not directly over the fire and the blue copper sulphate crystals at the bottom of the beaker begin to turn white.
- Word count: 560
Moles = Mass RMM Calcium = 40 Oxygen = 16 Hydrogen =1 = 1 = 1 40+(16�2)+(1�2) 74 = 0.0135 moles of calcium hydroxide The formula which the calcium hydroxide will react with the hydrochloric acid is: Ca(OH)2(aq) + HCL CaCl2(aq) + H2O(l) When balanced= Ca(OH)2(aq) + 2HCL CaCl2(aq) + 2H2O(l) The ratio in which the calcium hydroxide reacts with hydrochloric acid is 1:2. Therefore, to work out the mole of hydrochloric acid needed for this investigation is shown below: Ca(OH)2 + 2HCL Ratio = 1 : 2 Moles = 0.0135 : (0.0135�2)
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After recording the volume of sodium hydroxide required to neutralise the acid, I will repeat the experiment for the same vinegar so as to calculate an average. I will then perform the experiment again for the remaining vinegar concentrations, acquiring two results for each vinegar. From the averages of these results, I can then calculate the concentrations of ethanoic acid in each of the solutions using chemical formulae and my knowledge of the reaction. My prediction is that the solution which requires the most sodium hydroxide to neutralise it will have the highest concentration of ethanoic acid.
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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.
- Word count: 951
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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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.
- Word count: 825
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.
- Word count: 742
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.
- Word count: 985
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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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.
- Word count: 663