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# GCSE: Aqueous Chemistry

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## The rates of aqueous reactions

1. 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. 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. 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. 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.
5. 5 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

1. 1 The two most important equations to learn are:

moles = mass / Mr and moles = volume x concentration
2. 2 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. 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. 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. 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. 1 Anything that is dissolved in an aqueous solution will have the state symbols (aq). For Na+(aq)
2. 2 If your reaction is dissolved in water, then water will have the state symbol (l), for “liquid”.
3. 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. 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. 5 The most important equation reaction to remember is acid + base = salt + water. This crops up all of the time in exams!

1. ## Rates of Reaction - Chemistry

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It was held in place with a clamp stand. We had to ensure that there were no air bubbles in the cylinder or the measurements that we took would be inaccurate because it wouldn't have begun with zero gas in the cylinder. We placed the end of the tube and bung into the cylinder and measured out the appropriate amount of hydrochloric acid and poured it into a boiling tube. Next, we cut a strip of magnesium down to 2cm long and put it into the boiling tube, placing the bung in immediately and starting the stopwatch.

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2. ## Rate Of Reaction

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State of division: If you had lots of little chips and only a few big chips the smaller chips would react faster because there is more surface are, thus more particles, therefore more collisions take place. Catalysts: A catalyst is something that is used to speed up a reaction. It makes the bonds weaker, therefore its easier for a reaction to happen. With weaker bonds there is less energy to make the reaction work. Concentration of Reaction: As the concentration of a reaction increases, then there lots of colliding particles and the collisions being more successful and the rate of reaction increasing.

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3. ## RATE OF REACTION

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This is because increasing the concentration increases the probability of a collision between reactant particles because there are more of them in the same volume so therefore increases the chance of successful collisions forming more products when reacting with other elements, in this case when Hydrochloric Acid reacts with Calcium Carbonate, Carbon Dioxide is the has given off so the Higher the concentration of Hydrochloric Acid the higher the volume of Carbon Dioxide produced. Increasing the concentration of any of the reactants will increase the frequency of successful collisions as more particles will collide and the concentration of Hydrochloric Acid will increase and therefore increase the speed of products being formed.

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4. ## Determine the solubility product of calcium hydroxide

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Ksp is also known as the course of the equilibrium constant, and is constant at constant temperature. As predicted in the Le Chatelier's Principle, precipitate of solid Calcium Hydroxide will form when Ca2+ or OH- ions is added into a saturated solution of Calcium Hydroxide. Therefore, from the concentration of the Ca (OH) 2 in the saturated solution, we will be able to determine both the Ca+ and OH- concentration in the saturated solution. OBJECTIVE 1) To determine the solubility product of calcium hydroxide APPARATUS Burette, Pipette, Erlenmeyer flask, Beaker, Retort Stand, Filter paper, Funnel PROCEDURE Solution I : A saturated solution of Calcium Hydroxide in deionized water.

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5. ## Enthalpy of Neutralisation.

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Linking prediction to theory: The collision theory describes how the rate of reaction (the speed in which a reaction takes place) will increase as the concentration of hydrochloric acid increases. This is due to the knowledge that particles are closer together in a concentrated solution. The closer the particles are, the more often the particles collide. With more collisions comes a greater chance of the reactants reacting. This also explains why I can predict that the greatest rate of reaction will be found as the reactants have come into contact, as they are both at their highest concentrations, and the rate of reaction decreases as the reaction continues as the concentration of the reactants decreases.

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6. ## Heat of Neutralisation - I am going to investigate the heat of neutralisation between acids and alkalis.

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The experiments will always be carried out at room temperature so the initial temperature is the same. I will also repeat the experiments to obtain good results, if the results vary in any way I will calculate the average. Apparatus Measuring Cylinders Pipettes Thermometers Polystyrene Cup Safety To ensure the experiments are carried out safely I will always wear a lab coat and goggles. My hair will be tied up. I will make sure my work area is tidy and will observe all other laboratory rules. Method 1. Measure 25cm3 of acid into a polystyrene cup and take temperature. 2.

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7. ## Agar Diffusion Investigation

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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.

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8. ## 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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9. ## Concnetraion Hydorchloric Acid

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.

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10. ## The effetct of copper nitrate on the germination of mustard seeds.

these copper tolerant grasses have evolved due to selection pressuresbeing placed on the plants, which has inturn led those who are better adapted, copper tollerant, to survive providing them with a selective advantage. Prediction For this reason i predict copper nitrate will inhibit germination and growth of mustard seeds, especially at relativly low concentrations of copper nitrate as copper nitrate is toxic. if some of the mustard seeds do grow, this will only be due to chance or a mutation giving them a selective advantage in the environment.

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11. ## To find out how different concentrations of hydrochloric acid reacts with marble chips.

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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12. ## To determine the concentration of limewater

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Diluting hydrochloric acid: My first task for this experiment is to dilute the hydrochloric acid. To do this I first needed to work out how many moles I wanted for hydrochloric acid. For this part of my calculation I choose to use text book Calculations for chemistry to help me. Page..... Ca(OH) 2 (aq) + HCl (aq) --------> CaCl2 (aq) + 2H2O (l) 1gdm of Ca(OH) 2 Number of moles of limewater Mr of lime water= 40.1 + (16 x 2) + (1 x 2) = 74.1 Mass of lime water=1g Moles of lime water =mass(g)/Mr So 1/74.1=0.13 mol dm-3 Molarities of limewater solution: Morality = no.

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13. ## Anti-acids

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A catalyst breaks down a substance to provide a larger surface area to speed up the process. The Rate of Reaction The amount of time the reaction occurs. Magnesium + hydrochloric acid --> Magnesium Chloride + Hydrogen This equation gives me two possible methods of recording the rate of reaction: * Recording how fast hydrogen is produced from the reaction. * Or an alternative you can record how long it takes for the magnesium disappears on the reaction. There are three different factors that can influence the rates if reactions * The strength or concentration of the chemicals.

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14. ## equilibrium constant

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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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15. ## 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.

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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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16. ## Formula of a hydrated salt

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Mass = 0.79 g RFM = (1 x 2) + 16 = 18 Therefore 0.79 / 18 = 0.043888888889 mol To find the value of (x) in the formula FeSO4.xH2O you need to find the formula ratio. To do this you divide the moles of H2O by the moles of FeSO4. So 0.043888888889 / 0.004673512375 mol = 9.39 (3sf) = 9.4 (2sf) Therefore the ratio I have found is 1:9 for FeSO4:H2O. The 9.4 has to be rounded down because it is not possible to have 0.4 of a molecule, you have to make it an integer so you have a whole number of molecules.

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17. ## Handling Experiments,Observations and Data

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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.

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18. ## How oil is obtained, used and effects our world.

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This is known as fractional distillation. This shows the different heat at which some of the fractions boil at. As you can see the boiling points range from 20? to 400?. The different boiling points are important because this means that you can separate out the crude oil for the desired separate fraction. Some of the fractions are; Kerosene- a liquid hydrocarbon usually used to power aircraft or for heating. Naphtha- this is used to create a high octane gasoline.

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19. ## concntraion of calium hydroxide

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Since we are provided with a solution there is no particular danger. * When in contact with skin wash of with soap and water. Apparatus: * 250cm3 volumetric flask * 5cm3 graduated pipette * burette * pipette filler * white tile * clamp and stand * funnel * conical flask 250cm3 * 100cm3 beaker Balanced equation: Ca(OH)2 + 2HCl CaCl2 + 2H2O Dilution: Firstly I will calculate the approximate concentration of the calcium hydroxide in mol dm-3 Moldm-3 = gdm-3/Mr = 1/74.1 = 0.014 (3.d.p) Now I will use the balanced equation to work out the approximate concentration of HCl needed.

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20. ## To determine the concentration of a limewater solution

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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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21. ## Identification of an Organic Unknown.

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Universal indicator is a mixed indicator i.e. it is several indicators with different pH values mixed together. When added to solutions of different pH, different indicators change colour as above. The colour you see is a result of colour mixing. The colour has been linked to a specific pH and a colour chart provided. SAFETY: Follow general safety procedures and be aware that universal indicator can be dangerous so always make reference to the hazcards. 2. Test with Bromine Water EQUIPMENT: Test tube Pipette Bromine water PROCEDURE: Add several drops of bromine water into a test tube which if filled with 1cm� of the unknown substance.

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22. ## Rate of Reaction Investigation

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These below are the five best dilutions we came up with: Vol of Hydrochloric acid (cm�) Vol of Sodium Thiosulphate Solution (cm�) Vol of Water (cm�) Concentration (g/l) 1 10 50 0 40 2 10 25 25 20 3 5 50 5 40 4 5 25 5 20 5 2.5 12.5 7.5 10 After choosing my best five solutions we started to time each dilution. We repeated the method three times with the same solutions. This made my results more reliable and I was able to attain an average time for each dilution. Before doing my final experiment I tried different solutions to decide which one was the best to use and which was the most reliable every time by looking at the results for my final experiment.

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23. ## Chemistry Cwk Concentrations: Who's cheating on the vinegar?

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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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24. ## An Investigation of Titration

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The indicator will change colour when neutralisation occurs, also the temperature will stop rising. Choosing an Indicator I will find the best indicators to use in my experiment, the three indicators that I will compare are: Phenol Phtalein Methyl Orange Universal Indicator I will find which indicator is more beneficial for my experiment by filling a test tube with about 1/3 of Sodium Hydroxide and then adding a small amount of an indicator in, the first indicator I used was the Universal Indicator. As I added the hydrochloric acid to the sodium hydroxide it became neutralised and the colours kept changing as the substance changed from acid to alkali, it was very difficult to establish when you have reached neutralization as the colour changes to easily.

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25. ## The Effect of Concentration on the Rate of Reaction when you React Hydrochloric Acid with Marble Chips

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Collision theory states that the rate of reaction increases depending on how often and how hard the particles collide with each other in order to react. Therefore more collisions increase the rate of reaction because the number of collisions between the reactants increases. So, if there is a greater concentration (more particles between the water molecules) there is a greater chance of collisions. There are other factors that need to be controlled. The temperature can also increase the number of collisions because the particle energy is increased so there is a greater chance of collisions.

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