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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. ## To determine the concentration of Limewater solution

Also Ca(OH) is not very soluble. When is dissolves with HCl for example, only a little of the Ca(OH) will react as some of it will be left in the solution. In this planning, I also need to decide what experiment I am going to use to determine the concentration of Ca(OH). I used preliminary work to decide that the best method is titration. Knowledge from "determination of the relative atomic mass of lithium" (preliminary work). I have decided to use this method because it is a very accurate way of finding out the concentrations of substances. Titration is when you have your solution in a flask and have HCl, for example, above it in a burette.

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2. ## What factors affect the rate of decay of a limestone castle?

I think that if the acid concentration is high, then the marble chips will dissolve faster. If the concentration of acid is low or if acid is not present, the marble chips will dissolve slowly. I also think that the reaction between the calcium carbonate (marble chips) and the nitric acid will omit carbon dioxide, as shown in the equation above. This will become apparent whilst doing the experiment. I think that we will be able to see how much carbon dioxide is let off in each component of the experiment, due to how each one reacts.

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3. ## How the concentration of acid affects the rate of reaction?

Fill the chronicle flask with 20ml of hydrochloric acid. 6. Collect a limestone chip and weigh it before dropping it into the chronicle flask. 7. Start the stopwatch and record down every 20 seconds how much water has gone out of the measuring cylinder. 8. Repeat the whole procedure for each of the different molars of acid going from 1molar, 1.5molar, 2molar, 2.5molar, and 3molar. 9. Record all of my results in a clear results table. Equipment * Hydrochloric acid (different molars)

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4. ## Comparing the concentration of Vitamin C in a fresh fruit versus its carton juice

However, too much can cause bladder and kidney stones, thinning of the blood and loss of calcium from the bones. Sources of Vitamin C are mainly from citrus fruits, cress, fresh strawberries, pineapple and guava. Vegetable sources are tomatoes, green peppers, cabbage, brussels sprouts, broccoli and spinach. DCPIP is an indicator with a full name of Dichloroindophenol. It is dark blue in colour. When Vitamin C is added to DCPIP, the DCPIP turns colourless as it is reduced. L'ascorbic acid + DCPIP L'dehydroascorbic acid + DCPIP (Oxidised)

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5. ## Analysing; Enthalpy of Decomposition of Sodium Hydrogencarbonate

= 32.5 x 4.2 x 4.6 = 627.9 Joules Internal energy change = - 627.9 Joules Enthalpy change of neutralisation = Internal energy change No. Of moles of solid used = -627.9/0.0235 = - 26719.15 Joules/mol = - 26.7 KJ/mol Experiment 2 (T = T2 - T1 = 24.9 - 20.0 = 4.9 0C Energy transferred to surrounding = m x c x (T = 32.5 x 4.2 x 4.9 = 668.85 Joules Internal energy change = - 668.85 Joules Enthalpy change of neutralisation = Internal energy change No.

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6. ## The basic aim of this experiment is to determine the percentage concentration of Iron (II) that is contained in lawn sand. By carrying out a series of titrations as outlined below, hopefully, the percentage of iron can be determined.

+ 8H+(aq) + 5Fe2+(aq) ((( Mn2+ (aq) + Fe3+(aq) + 4H2O (L) If we were to titrate 20 cm3 of the solution with 25 cm3 of Potassium permanganate the following amounts of moles of iron (II) is required: No. of moles of KMnO4 required = volume x concentration = 20/1000 dm x 0.02 moldm-3 = 4.0 x 10-4 moles = the number of moles of MnO4- No. of moles of Fe2+ = 5/1 x no. of moles of MnO4- = 5 x 4.0 x 10-4 moles = 2.0 x 10-3 moles = number of moles of FeSO4 contained in solution Mass of FeSO4 = Mr x number of moles = (55.8 + 32.1 + 16.0x4)

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7. ## Water Pollution & Sewage Disposal

The reed bed is sited over the landfill, and shows that it is possible to locate artificial wetlands on the stabilised and pre-lined surface of landfills. Water Pollution Facts Water has the remarkable ability to renew and cleanse itself. When waste materials are deposited into a receiving stream, they often settle out, break down, or become diluted in the stream. Pollution can occur if too much of a substance or too many substances are discharged so that it overwhelms the capacity of the stream which turns the un contaminated water into a pollute substance.

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8. ## An Investigation into the Heat of Neutralisation

The heat given off can be measured in each reaction by changing it into joules of energy. Heat of neutralisation is the heat change given form an acid and an alkali reacting together to form one mole of water. Deciding on a method: Although there are many ways of investigating heat of neutralisation for this experiment I will only look at one. Methods that I could use include varying the volumes of both acid and alkali together or just one.

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9. ## Mining With Microbes

Smelting copper ore by traditional methods had cost between \$130 and \$200 per kilo. The introduction of biohydrometallurgy cut the cost to less than \$70 per kilo. Production of one tonne of copper by smelting typically results in two tonnes of sulphur dioxide being pumped into the atmosphere. Biological extraction avoids this. Biohydrometallurgy is straightforward when applied to copper production. First, the low- grade ore, and tailings left from any earlier conventional mining, is piled up in an area where the ground has been made impermeable. It is then sprayed with an acidic leaching solution containing T ferro-oxidans and T thio-oxidans (see Figure 2).

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10. ## What Factors Affect The Cooling Of A Liquid

If I have a lid, the heat will then be stopped from escaping into the air through the top. As shown below- Equipment * Timer- this is to time the amount of time the liquid is in the container. This will make sure that the time will be the same for each experiment. * Data logger and Thermometer- this is to take the temperature of the water. I will use two forms of identifying the temperature. This way I can compare the two results and see if there are any drastic differences.

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11. ## The aim of the experiment is to find out which indigestion tablet is the best. We can do this by looking at how much alkali is put in after the tablet has been put in.

These hydrogen ions are produced when an acid reacts with water: HCl (g) + water ==> H+ (aq) + Cl- (aq) Hydrogen ions can be measured on pH scale. If it's an acid then the pH is always below a pH 7. Alkalis always contain OH- ions. They are the Hydroxides. The most commonly known Hydroxide is Sodium Hydroxide (SHO). Hydroxides have a pH of above 7. If the hydrogen ions and the hydroxide ions are put together, they form water (H2O). This is called neutralisation. The equation for this is below: H+ (aq)

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12. ## Find the exact concentration of an acid solution

Apparatus: * burette * clamp stand * pipette * conical flask * volumetric flask * white tile * weighing bottle * balance * funnel * distilled water * methyl orange indicator * sulphuric acid * solid anhydrous sodium carbonate Quantities: The sulphuric acid supplied is believed to have a concentration of between 0.05 and 0.15 mol dm��, so I plan to make up a sodium carbonate solution with a concentration of 0.1 mol dm�� as this is the mid point.

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13. ## How does changing the concentration of hydrochloric acid effect the rate of reaction between hydrochloric acid and magnesium ribbon ?

Next to the bowl of water I will have a water bath which I will keep at 30 degrees Celsius in this is where test tube will stand this test tube will hold 25mm of hydrochloric acid and a piece of magnesium ribbon (5cm). There will be a bung and delivery tube from this test tube that will deliver the gas released from the reaction to the measuring cylinder so it can be measured. I will need to measure the gas from the bottom of the meniscus every 10 seconds during the reaction from the 100cm-cubed measuring cylinder.

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14. ## Rates of Reaction

For a chemical reaction to occur though, there must be reactants which when mixed may cause a chemical reaction. This in turn creates a product or outcome. In this experiment the reactants will be the hydrochloric acid and the magnesium ribbon. As soon as the magnesium is put into the acid and touches it the chemical reaction will start to take place. When a chemical reaction occurs, the particles which combine need to meet up with each other (collide) so that they can swap or share electrons.

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15. ## Find the accurate concentration of a solution of sulphuric acid acid of which concentration is thought to be between 0.05 and 0.15moldm-3

The concentration of the H2SO4 is thought to be between 0.05 and 0.15 moldm-3 . Assuming the concentration of the acid to be 0.05 moldm-3, the concentation of Na2CO3 can be calculated as follows: Conc of H2SO4 (c) = 0.05 moldm-3 Volume of H2SO4 (v) = 25cm3 = 0.025dm3 Number of mole (n) = cv = 0.05 x 0.025 = 0.00125mols 0.025dm3 of Na2CO3 solution will contain 0.00125mols of H2SO4 concentration of Na2CO3 = n/v = 0.00125/0.025 = 0.05 moldm-3 n = mass/ relative molecular mass number of moles (n)

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16. ## Investigation to find out if vinegar from chip shops is watered down

the concentration at 0.1 took too long to neutralise the vinegar and I wouldn't have time to use this and the concentration at 1.0 neutralised the vinegar after a few drop therefore the results would have been too inaccurate. So I went with the one in the middle at 0.5m which neutralised the vinegar in a reasonably amount of time. The titration technique for carrying out this neutralisation reaction is very accurate; this is because the apparatus used is calibrated to give a high degree of accuracy in the measurements made.

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17. ## Factors Affecting the Amount of Carbon Dioxide given off when a Carbonate reacts with an acid

Type of carbonate Some carbonates such as Sodium are soluble, therefore I will not be able to investigate. In my investigation I have chosen to investigate the amount of carbonate rather than the type of carbonate as amount is a continuos variable and will produce a pattern rather than a random collection of carbonates. Constants The following variables will be kept constant: Variable Control of variable Temperature Room Temperature Type & Concentration of acid 2M Hydrochloric Acid Amount of Acid 50ml Pressure Atmospheric Type of carbonate Calcium Carbonate Rate of stirring None Fair Test In order to make this investigation as fair as possible, all the constant variables must remain constant throughout the experiment, as mass of carbonate is the only variable changing.

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18. ## Find out the effect of concentration on the rate of reaction between marble chips and acid.

This is because there are more Hydrochloric acid molecules in a higher concentration. I predict that if I double the concentration the rate of reaction will also double. I predict that the concentration is directly proportional to the rate of reaction. Variable type Variable Value(s) Reason Input Concentration of Hydrochloric acid. 1 - 5 M This range will provide us with a good range of results. 5M is the highest concentration available to us. Outcome Rate of reaction Unknown Measured in the experiment. Rate cannot be measured directly. The time the marble chips takes to dissolve, will be recorded.

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19. ## Investigation looking At the Speed of Reactions

I used a preliminary test to help in the prediction. I went and prepared marble chips and concentrated acid we tried the experiment, the results was clear that as in a few seconds it was almost finished. When we used very dilute acid it took so long for it to react and the amount of bubbles were much less than the first one. By using the results I can make the prediction of that, the rate of reaction is affected by concentration.

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20. ## To Investigate the Effect of Changing the Concentration On the Rate of Reaction In Two Experiments

The rate can then be calculated by dividing 1 by this value. Diagram: Safety: one of the reactants, hydrochloric acid is corrosive so skin contact with it will be avoided. Sulphur dioxide, a toxic gas, will be produced during this reaction. Therefore, I will not stand over the apparatus to avoid inhaling it. Also, the reactants will be disposed of in a fume cupboard when the experiment has finished. List of Apparatus: * 250ml conical flask, chosen because the thin neck limits sulphur dioxide emissions, and the broad base makes it easier to see the cross on the filter paper without standing directly over the experimental.

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21. ## Magnesium Sulphate (MgSO4) as an Anti-Inflammatory Agent Investigation

In a strong acid nearly all the molecules form ions while in weaker acids fewer Hydrogen molecules form ions. When Magnesium reacts with Sulphuric Acid the acid molecules which split up and Hydrogen gas disperses Word equation: Magnesium + Sulphuric Acid Magnesium Sulphate + Hydrogen Symbol equation: Mg (s) + H2SO4 (aq) MgSO4 (aq) + H2 (g) All factors that affect the rate of reaction in this experiment are the concentration of the acid, temperature of which the reaction is performed, surface area of the Magnesium ribbon and the presence or absence of a catalyst.

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22. ## The Erosion of Marble

My controlled variables are; > the mass of marble which I use as it will take longer to erode it. > The size of marble which I use i.e. Try and have the same weight of marble have the same approximate surface area. > I will keep the temperature constant as the rate of reaction may increase as temperature increases. > I will keep the volume of acid used constant as this may also change the rate of reaction My dependent variable will be the mass of CO2 given off with time.

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23. ## To determine the relative atomic mass of Lithium

After setting up the apparatus, I went on to measure my Lithium metal. The Lithium metal was kept in oil because of it reactive nature. Before measuring the Lithium's mass, I cleaned up the oil in because it might affect the rate of reaction. Once the oil is totally dried from the Lithium metal I took the measurement, which was 0.11g. I then went on to put the Lithium into the distilled water in the conical flask. Immediately when the Lithium was put in the distilled water, I inserted the stopper so that they will not be any lose of Hydrogen gas.

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24. ## How Does the Temperature of Hydrochloric Acid Affect the Rate of Reaction Between Hydrochloric Acid and Magnesium?

is the best. At first, I planned to use 50% acid (10 water and 10of acid) but when find out that the hydrogen given out are so fast that which is very hard to measure. It is also very hard to draw the graph if not enough results are collected, Also because of very little volume, it is very hard to control the temperature, so I decided to use 20of acid and 40of water which is about 33% acid is the best, it is much more easy to control the temperature and the speed of giving out hydrogen are not too fast.

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25. ## Does changing the temperature of the acid affect the speed of reaction?

To make it even safer, I will protect my eyes just incase anything goes wrong, using goggles. Then I will put the magnesium ribbon in the acid and what should happen is that the magnesium ribbon reacts with the acid and makes hydrogen. After that I will see how far the gas syringe moves in every 10 seconds up to 130 seconds because of the gas made by the magnesium and the hydraulic acid. I will do this investigation three times and then find the average to get a more reliable set of results.

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