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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!

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  1. The flood

    ceiling, as it collapsed bringing with it plasterboard and water, we were soaked and wondering if things could get any worse when the microwave gained a mind of its own and burst into life! The microwave was by now, understandably quite unhappy about the water it was receiving in this highly unusual storm, there were snaps and jolts resounding from it, the floor was filling up around my feet, time for more action. A bucket here, a saucepan there, "Yes", I thought to myself, "The great saviour in action."

    • Word count: 943
  2. The purity of aminosulphonic acid

    22.53 cm3 is average amount of acid (H2NSO3H) reacted with 25.00 cm3 of alkali (NaOH) with concentration of 0.200 moldm-3. Now I am going to work out the number of moles of NaOH in 25.00 cm3 of that with concentration of 0.200 moldm-3: CV=M C=0.200 moldm-3 M=0.200*25.00/1000=0.005 number of moles of NaOH V=25.00 cm3 reacted with acid. M=number of moles As the ratio of the acid to the alkali in the reaction is 1-1 so number of moles of the acid reacted with the alkali are as same as number of moles of the alkali reacted with the acid because of ratio of 1-1.

    • Word count: 630
  3. Autobiography of Gold

    I start getting angry at 1064�C but if I cannot still control myself until I get to 2861� C, which is when I start boiling I get very violent and . Some people think my family is too big. Well in a sense, I do have a big family. I am in a family more widely known as metals; more specifically transition metals. However, on the dark side, we don't usually interact with each other because we cannot produce much anything by working together.

    • Word count: 733

    Our results were recorded in a data table. Benedict's test - for simple (reducing sugar): A small amount of each unknown liquids was taken in three separate boiling tubes. To each of them Benedict's solution was added. All three tubes were heated gently for 2 minutes in the waterbath. A colour change from blue to orange was searched and the result was noted in the table. Iodine test - for starch: A small amount of each unknown liquids was taken in three separate boiling tubes.

    • Word count: 593
  5. Explain the imagery or theme of the poem called Rising Five

    This is an excellent ambiance to be in during any festival and everyone in the town enjoys it. Each and every person has a marvelous time. It is like living the happiest moment of your life to the fullest. There are different groups of people in every area. To make it more fun I and my friends would play pranks on everyone even if it is an adult or a small boy or girl. Water is thrown to everyone as this festival also combines with water.

    • Word count: 492
  6. Which is the correct equation?

    matt * Bunsen burner * Glass weighing bottle Chemicals: * Powdered potassium nitrate Safety Precautions: * Wear safety glasses at all times to avoid potassium nitrate entering the eye. Should this occur however, immediately wash eyes with water for 10 minutes and seek medical help. * Clean up any spillages immediately. * Any skin contact with the substance, wash with water immediately. * Wear a lab coat at all times to avoid contact with clothes etc. * To reduce the risk of burns, always hold the Bunsen burner at the bottom, and leave all apparatus to cool before touching it.

    • Word count: 896
  7. Qualitative AnalysisCalcium chlorideLead nitrateCopper sulphatePotassium sulphateIron chlorideSodium carbonate

    Negatively charged ions are detected in solution by specific tests. In this practical, I have to detect the presence of the following positively charged ions: Na+, K+,Ca2+, Cu2+, Pb2+,Fe3+ And the following negatively charged ions: Cl-,SO42-,CO32- All of the negative charged ions I am identifying all colourless. Risk Assessment Substance/Apparatus Hazard Risk Precaution Emergency Action Glassware Dangerous if glass is broken. Low risk and perfectly safe if used properly. Do not try to pick up pieces of broken glass with your hands, especially from a wet sink.

    • Word count: 758
  8. The biological signficance of water

    Water is the most universal of solvents and though polar in its make up, it exhibits properties that indicate a sort of polymerizing link between its molecules similar to heavier organic non-polar compounds. While it exists on earth in all three basic states, solid, liquid, and gas, water's properties are often bizarre by most standards. For example liquid water contracts when cooled until it reaches a temperature of about 4 degrees Celsius where it reaches its maximum density. When this temperature is reached liquid water begins to expand, and even with a change in state to ice, water continues to expand, by reducing its density as its temperature decreases.

    • Word count: 984
  9. Extracting fats

    The polar end attracts polar water molecules. The other end, hydrocarbon end, attracts oils and other water insoluble materials like fat or grease. Water is a polar solvent and dissolves polar and ionic molecules Method * Add 10 ml of oil to a beaker * Add 10ml of 40% sodium hydroxide(corrosive) * Heat the solution till it boils * Use a spatula to add sodium chloride till it goes semi solid. * Add perfume or scented liquid * Leave the soap to dry and then take PH.

    • Word count: 564
  10. Testing For Non-Reducing Sugars

    * Stand the Tubes in a Boiling Water Bath by using a rack and leave for 5 Minutes. Remove the Rack with all the Test Tubes and leave to cool for a short period of time. * Carefully add Sodium Hydrogen carbonate to the solution in the tubes, this should cause a reaction to occur where the solution fizzes.

    • Word count: 442
  11. How does the poet convey a sense of the importance of water to this community? The poem "Blessing" was written by Imtiaz Dharker. The poem is set in a slum in India

    The human or seedpod would die. The second sentence is very direct and clear telling us exactly what the poem is about, the lack of water. "Imagine the drip of it, the small splash, echo in a tin mug," This quote contains onomatopoeia to make the reader think of the sound water makes when it splashes. The poet talks of how water leaves an echo when it splashes. The word echo could be said to be referring to water in this community and how like an "echo" it slowly disappears.

    • Word count: 810
  12. How Much Acid there is in a Solution

    = Number of moles (in mol) � volume (in dm3) When working out the concentration of the sulphuric acid, it is immediately clear that it has the same number of moles as the sodium carbonate solution, as the molar mass ratio is 1:1. Concentration of sodium carbonate solution: Calculating the number of moles first: Relative formula mass ( RFM ) of Na2CO3 : ( 23 x 2 ) + 12 + ( 16 x 3 ) = 106g Amount of sodium carbonate used at the start of the experiment was 2.65g.

    • Word count: 651
  13. The aim of this experiment is to compare the volume of CO2 produced as the concentration of acid used to react with the base is changed.

    If the number of moles of acid used were changed, the number of moles of CO2 produced would change. This would also change the volume of CO2 produced as 1 mole of gas occupies 24,000 cm3, therefore a different number of moles of CO2 would produce a different volume of CO2. Preliminary method * The variable that I am testing for is the concentration of acid. Therefore a range of different concentrations of acid is required. This can be done by starting with 2M acid and diluting it to the required concentration. Also an excess amount of carbonate would need to used.

    • Word count: 917
  14. The aim of this experiment is to determine the concentration of a limewater solution by method of titration.

    Volume of 2HCl = 0.000337 dm� = 0.337cm3 The volume of HCl is too small to titrate and therefore I will multiply the volume by x100. To do this I need to divide the concentration of the acid by 100. (2moldm-3 will be 0.02moldm-3) Method of dilution: Apparatus: * 5cm3 graduated pipette * 50cm� burette * 250cm� volumetric flask * funnel * burette stand * 250cm� of limewater * Hydrochloric acid and concentration 2mol dm-3 * 1g dm-3 of Calcium hydroxide (present in limewater)

    • Word count: 708
  15. Aim To produce synthetic aspirin. To calculate the percentage yield of the aspirin produced. To compare the aspirin produced in the lab with tablet aspirin and aspirin from the lab by there melting points

    The flask and its contents were reweighed. > In a fume cupboard, 20cm3 of ethanoic anhydride was added by a measuring cylinder, to the 2- hydroxybenzoic acid. The flask was swirled as it was added to ensure thorough mixing. > 5 to 10 drops of concentrated sulphuric acid was added to the mixture. > The flask was placed on a hot plate, in a fume cupboard and the mixture heated to about 85oC it was kept at this temperature for about 10 minutes, it did not go over this temperature as if it did the compound may of decomposed.

    • Word count: 829
  16. Aim: Our aim is to find out and investigate the boiling temperatures of water and water with impurities.

    Method: First of all, gather together these four impurities: Sugar, Salt, Cornstarch and Baking soda. Pour 10 mL of water into a measuring cylinder, and then add 10 mL of sugar and mix with a spatula until it dissolves, and pour this mixture into a beaker. Follow the same procedure for the rest of the 3 impurities. Remember to wash out the measuring cylinder after every mixture of the 4 impurities other wise... This won't be a very fair test! Now then, you should have four beakers in which contains: Sugar + water, Salt + water, Cornstarch + water and Baking soda + water.

    • Word count: 847
  17. Titration with HCl and NaOH

    Step 4. Add 4 or 5 drops of methyl orange indicator to the contents of the flask. Note the colour. Step 5. Using the tap on the burette run the acid into the solution of sodium hydroxide in the conical flask (shaking the flask as the acid drips in) until the solution changes colour. At this point note the reading on the burette and the colour of the indicator. This first titration is 'rough' so only an approximate volume of acid is required. Step 6. Repeat steps 2, 3 and 4 Step 7. This time: i.) Run the acid into the solution until the volume of HCl is to within 2 cm3 of what it was in the rough titration (step 5).

    • Word count: 897
  18. Determining the equilibrium constant for the hydrolysis of Ethyl Ethanoate Definition

    In hydrolysis of ethyl Ethan ate, the reaction produces ethanoic acid (CH3COOH) and ethanol (C2H5OH). Hydrolysis of esters - Esters break down into their respective organic acid and alcohol from which they are formed. Hydrolysis means to 'split with water'. A number of organic compounds undergo hydrolysis, such as amides, esters and halogeno-alkanes. In the overall process of hydrolysis, a bond in an organic molecule is broken, and an O-H bond in a water molecule also breaks. Then, from the water molecule, an O-H group adds to one part from the organic molecule, and an H atom to the other.

    • Word count: 955
  19. Flame Test

    Then place the loop in the hydrochloric acid and then place in the flame. * Place the loop in the salt and then place it in the flame. * Record the colour of the flame * Repeat the test for the other four salts and record what colour the flame becomes. * In between each test sterilise the loop so the test will not get contaminated. Safety * When suing the Bunsen burner make sure there that there is nothing close to your working area which is flammable. * Wear gloves and goggles to protect your eyes and hands.

    • Word count: 592
  20. Chemistry - What is the atomic mass of lithium? Method one: The first method involves reacting a known mass of lithium with a known volume of distilled wa

    1. This was my rough titration, I did this to find, where the titration became neutral. 2. This titrated was very close but I think went too far. 3+4 where very close titrations which is really what I expected. It is easy to see from my table tat the results I have recorded do not following 3 significant figures like the rest of my results. I have done this for a deliberate reason. This section is so crucial that I think it is reasonable to get the highest degree of accuracy I can find.

    • Word count: 948
  21. To distinguish between the 5 aqueous solutions there are a number of tests and experiments that can be carried out. The tests are best explained as a method and a detailed analysis of the reactions is added further on

    The one goes milky (white precipitate) from colourless is the Calcium hydroxide so this can be eliminated. Label it. 2) The remaining 4 samples are still useable for the next test so, add 10cm3 of silver nitrate to all 4 of the solutions. One solution should give a cream precipitate (Bromide) and another should give a white precipitate (Chloride). 3) Separate the two samples and to these, add excess ammonia. The one which dissolves is silver chloride. Potassium Bromide and Sodium Chloride have now been eliminated. Label them. 4) The remaining solutions should be disgarded (the ones with silver nitrate in)

    • Word count: 718
  22. My prediction is the higher the concentration of HCL the quicker the Sodiumthiosulphate will react with it.I think this because there are more particles colliding with each other

    Measuring cylinder Fair test: To make the experiment fair we repeated it two times on the same day so that the room temperature was the same throughout the test. We cleaned the equipment after the experiment so they were clean and did not have any of the mixed solution left in it. Method: Our method was- * Collect apparatus * Set up apparatus * Pour 25 ml into beaker of HCL * Pour 25 ml Sodiumthiosulphate * Set timer * Start the timer when solutions are together * Record time * Repeat using 1mol * Repeat using 0.5mol * Repeat using 0.25mol * Repeat using 0.125mol * Repeat and record time Results: Test 1 Hcl (MOL)

    • Word count: 668
  23. Aim/Objective: To find out the dissolved oxygen content (in mg dm-3) in a water sample by titration of iodine against thiosulphate solution.

    = 24.7mgdm-3 5) Discussion: A number of precautions needed to be carried out in the experiment. First of all, the volumetric flask should be filled completely with the water sample, because if some spaces were spared in the flask, oxygen in the spaces may dissolve into the solution, increasing the calculated dissolved oxygen content in the sample. In contrast, some of the dissolved oxygen in the sample may evaporate into the spaces, giving smaller dissolved oxygen content. Also, when filling any solution into the volumetric flask, no air bubbles could be trapped. This is because any air bubbles may increase the oxygen content in the volumetric flask, increasing the dissolved oxygen content in the sample.

    • Word count: 829
  24. The group II elements are beryllium, magnesium, calcium, strontium, barium andRadium. The appearances of the Group II elements are all metals with a shiny, silvery-white colour.

    Ionisation energy decreases due to extra shielding from inner shells and increase in distance from the nucleus. Other properties are that the group II elements are good conductors of electricity, there compounds are colourless and in all their compounds they have an oxidation number +2. Uses The uses of group II elements are used widely in the commerce and industry. The bright white flame of magnesium is used in flares. It also has a very strong reducing power that it is widely used to protect steel objects, like ships for example. The strong reducing power also means that it can be used to extract less electropositive metals.

    • Word count: 650
  25. The Memorable Trip

    It was two of my cousins, I quickly said hello to them. I had overslept and no one bothered to wake me up. I then asked Kevin and Elaine if they were coming on the trip, and they said unexcitingly, "Yes, we are coming fishing!" Fishing? I had never even thought of that. I was shocked but excited at the same time as I had never been fishing before. The fishermen knew my dad really well. I always thought that going fishing was just to get on the boat, go out on the ocean, throw the line and wait for the fish to bite, but I was totally wrong.

    • Word count: 865

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