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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. ## What is Ammonia?

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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2. ## Investigate the reaction of Calcium with Water.

Collect hydrogen gas evolved using an inverted measuring cylinder 3) Measure the volume of hydrogen evolved at 40-second intervals Results: Time/s Volume/cm� 0 0.0 40 1.25 80 2.25 120 3.0 160 3.2 200 3.4 240 3.6 280 3.8 320 3.8 Observation: As the calcium reacted with the water, I observed the calcium effervescing, and the calcium moved up and down in the cylinder during the reaction. As the reaction progressed, the piece of calcium gradually dissolved smaller and smaller until it was completely dissolved in the water.

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3. ## To investigate the rate of reaction between Sodium Thiosulphate (-Na - _2 S_(2 ) O_3) and Hydrochloric acid (HCl)?

I will be doing this investigation in many different ways such as varying the temperature or the concentration of the hydrochloric acid and also I will use a calorimeter which will give me an accurate reading of how much light is absorbed and when the solution has turned cloudy and no light can transmit through it. This is the word equation for this reaction: Sodium Thiosulphate + Hydrochloric Acid Sulphur Dioxide + Sulphur + Water + Sodium Chloride The reaction can also be expressed as a symbol equation: Na2S20 3 + 2HCl SO2 + S + H20 + 2NaCl Apparatus: 1.

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4. ## rate of reaction between sodium thiosulphate and hydrochloric acid

Therefore we can say that the effective collision frequency also increases and thus increases the rate of reaction. Variables: Independent * The concentrations of hydrochloric acid. * Volume of water * Volume of Hydrochloric acid Dependent * Time taken for the cross to disappear. * Colour change of the sodium Thiosulphate and hydrochloric acid. * Change in temperature after the reaction is over. Constant * Volume of hydrochloric acid used. * Volume of sodium Thiosulphate used. * Concentration of sodium Thiosulphate * Surroundings * Room temperature Molar calculations to calculate the concentration of HCl after diluting it with water: The molar value of HCl in a solution can be calculated for each dilution.

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5. ## Rates of reaction between Sodium Thiosulphate and Hydrochloric Acid

I completed this experiment to test my method and gather an initial set of set of results. After I successfully completed my preliminary experiment I set out to collect my official set of results. I planned to make this series of tests more accurate so I could therefore collect a more reliable set of data. Method 1. Set up the conical beaker on a laminated cross, and two sets of burettes, one to measure out distilled water, and the other for measuring sodium thiosulphate.

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6. ## Identification of an organic unknown

Apparatus and reagents * Bromine Water * Test tubes/Test tube racks * Acidified Potassium Dichromate (VI) (K2Cr2O7) * 2, 4-Dinitrophenylhydrazine (2, 4-DNP) * 5% Aqueous Sodium hydrogen carbonate (NaHCO3) * Water Cooled condenser * Clamp and stand * 20 ml - 400 ml Beakers * Measuring Cylinder * Bunsen burner * Phosphorous Pentachloride (PCl5) * Ethanoic acid * Iron (III) Chloride (FeCl3) * Sodium metal (Na) * Tollens Reagent * Sulphuric Acid * Jones's reagent (CrO3-H2SO4 in H2O) * Water bath * Bunsen burner/heating Mantle * 1 ml of 0.5 mols hydroxylamine hydrochloride * Sodium Hydroxide (NaOH)

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7. ## Experiment on The Use of Analytical Balance in Determining the Water Content of a Given Hydrated Salt

To find the mass of the water, we weighed the hydrated salt and then heat the hydrated salt in order to obtained the mass of the dehydrated salt, then the mass of the hydrated salt minus with the mass of dehydrated salt. To weigh the mass of the salt accurately, we use analytical balance and the two-decimal balance to check the accuracy of the mass obtained. Analytical balance is an instrument used to measure mass to a high degree of precision.

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9. ## Investigating the effect of changing temperature on the rate of reaction between sodium thiosulphate (Na2S2O3) and hydrochloric acid (HCL).

Method * Start by setting out the equipment in the right places for you. * Then measure out volumes of water (10cm�) and sodium thiosulphate (40cm�) in the larger measuring cylinders and mix them together in the beaker. * Measure out the 5cm� of hydrochloric acid but keep it separate from the water and the sodium thiosulphate in a smaller measuring cylinder to be more accurate. * Heat the mixture to the desired temperature. * Place the heated mixture on the cross marked paper and quickly add the hydrochloric acid to the mixture. As you do this, start the stopwatch.

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10. ## Preparation of standard solutions.

Requirements: - 1 burette (25 ml) - 2 beakers - 3 calibrated flasks (500 ml) - 1 plastic bottle (1500 ml) - 0.5% solution of phenolphthalein - 0.1 mol dm-3 NaOH (1 dm3) - balance - lime water Method: Titrating the solution of NaOH over potassium hydrophtalane to calculate the exact concentration of the solution of NaOH. Procedure: 1. I measured accurately about 5 g of sodium hydroxide and dissolved it in 1 dm3 of lime water. 2. On the analytical balance I measured 0.5-0.9 g of potassium hydrophtalane and dissolved it in 70 cm3 of water.

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11. ## Blessing: Creative Writing

It was like living in a hell on earth except the fiery overlord is the sun. People didn't want to look up in the sky because if you did the sun would probably burn your eyes out. There wasn't a cloud in the sky. We all decided to make sure we had no pets because we would have to give them water too and it would be a waste. When you walked outside the ground would melt the bottom of your shoes.

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12. ## Relative atomic Mass of Lithium

The 100cm3 of water measurement from method 1 would be used to work out the concentration, so an error could just affect the results. These results are the tolerance values for each piece of equipment used within the experiment. * 10cm3 Pipette- (+ or -) 0.04cm3 * 100cm3 Pipette- (+ or -) 0.15cm3 * 250cm3 Measuring cylinder- (+ or -) 1cm3 * Burette- (+ or -) 0.04cm3 * Balance- (+ or -) 0.005g The equipment used within this experiment played a major role, and so whenever making a measurement I always considered the fact that any errors in my measurements would have an effect later on during my investigation.

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13. ## Are all Saccharides Reducing Sugars

After the two minutes are up I will take the test tube out of the water to check if it has changed colour and will record the results whether it has or not. If any of the sugars do not change colour then I will place the sugars that don't change in fresh test tubes, I will then add 4/5 drops of hydrochloric acid and then place the test tubes into the water bath for 3 minutes. We then take the test tube out of the water bath and slowly add sodium bicarbonate a small amount at a time until

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14. ## Aim: To Determine The Concentration Of a Limewater Solution

Hydrochloric Acid Concentration The HCl provided for this experiment is far to concentrated my experiment. It would react with the limewater too quickly hence giving unreliable results. Therefore, I will have to dilute it, using the standardization technique. First I would need to find what would be an optimal concentration for the HCl. (molar mass of Ca(OH)2= 74.1) Converting the g dm-3 to mol dm-3 of the limewater. Concentration (g dm-3) / Molar Mass = Concentration (mol dm-3) 1 / 74.1 = 0.0135 0.01 mol dm-3 limewater concentration (3 s.f)

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15. ## Acid-Base titration of Sulphuric acid and Sodium Hydroxide

This is known as neutralization by titration. Titration is a technique used to find the concentration flask. The acid solution is then added in small quantities from the burette. Since the concentration of one of the solutions is known, the concentration of the other solution can be determined from the end-point of the titration. To show when neutralization has been reached, an indicator is used. A suitable indicator is phenolphthalein. This indicator is colourless in acid and pink in an alkaline solution. The end-point of this reaction is determined when the colour changes from pink to colourless.

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16. ## Colorimetric Determination of Manganese in Steel

+ 2 NO3- (aq) + 8 H+ (aq) --> 3 Mn2+ (aq) + 2 NO (g) + 4 H20 (l) Then the manganese ions were oxidised into permanganate ions using the oxidising agent, potassium periodate: 14 Mn2+ (aq) + 16 H20 (l) + 10 I04- (aq) --> 14 MnO4- (aq) + 5 I2 (g) + 32 H+ (aq) Procedure The apparatus used for the experiment were: 50cm3 and 100cm3 standard flasks 50cm3 burette spectrophotometer optically matched cuvettes balance 50cm3 and 250cm3 beakers bunsen burner 10cm3 and 50cm3 measuring cylinders clock glass filter funnel tweezers wash bottle dropper wire cutters steel paper clips 0.0010 mol

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17. ## Determining the relative atomic mass of lithium

To protect clothes from the chemicals an apron should be worn. o Method 1 results: 0.10grams of lithium produced 172cm3 of hydrogen gas, moles of H2 collected: H2 produced = 172cm3 = 7.167�10-3moles 24000cm3(1 mole of gas) 24000cm3 2Li(s) + 2H2O(l) � 2LiOH(aq) + H2(g) - molar ratio of Li to H2 is 2:1 therefore; the amount of moles of lithium that reacted = 7.167�10-3moles � 2 = 0.0143moles Relative atomic mass of lithium = mass = 0.1000g = 6.99g mol-1 moles 0.0143mol o Method 2 results: titration 1 2 3 4 initial (cm3) 0.0 0.0 0.0 0.0 final (cm3)

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18. ## Acid Base Characteristics of Oxides Across the periodic Table

Observe and record the reaction. 4. In the third test tube add Sodium Hydroxide in an appropriate amount. Observe and record the reaction. 5. Repeat these steps for Magnesium Oxide (MgO), Aluminium Oxide (Al2O3) and Silicon Oxide (SiO2). NOTE: Phosphorus Pentoxide and Sulfur Dioxide were performed by the teacher. Data Collection: Table 1: Appearance Of Oxides Oxide Name Appearance Sodium Oxide White (creamy), crystallised, clumped Magnesium Oxide Powdered, white, very fine, fluffy, slightly grainy Aluminium Oxide Extremely fine powder, white, silky Silicon Dioxide Beige brown colour with darker and lighter specks, grainy Phosphorus Pentoxide White fine powder Sulfur Dioxide Clear colourless gas Table 2: Reaction Of Oxides With Water Oxide Name Reaction pH Acid/Base Observations Sodium Oxide Yes

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19. ## Fruit and Vegetable Batteries

What I found: I found that the fruit that gave off the highest voltage was an orange,- and highly acidic, which led me onto investigation 3, and the question- do acidic fruits give off a higher voltage?

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20. ## A2 Chemistry -Assessed Practical In theory the remaining mass after the heating will be only FeSO4, so from this the mass that was evaporated off would be entirely water. From this we can calculate

Sulphate Crystals is FeSO4.6 H2O. Method 2 Titration # Start Vol. (cm�) End Vol. (cm�) Difference (cm�) 1 9.0000 30.9500 21.9500 2 11.0000 33.1500 22.1500 3 15.0000 37.2500 22.0500 4 4.0000 26.1000 22.1000 Average (cm�) 22.0625 Equation 5 Fe2+ + MnO4- + 8 H+ = 5Fe3+ + Mn2+ + 4H2O By finding the number of moles of Fe2+ ions being reduced by the MnO4- ions we can calculate the Mr of the FeSO4.xH2O that was used in the experiment. Calculations 22.0625 / 1000 = 0.0220625 dm � Using n=VxM 0.0220625 x 0.01 = 2.20625x10-� moles of Fe2+ From the equation

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21. ## an investigation about investigating various metal carbonates and hydrochloric acid such as calcium carbonate, Iron carbonate etc.

The only factor I will have to change is the different types of metal carbonates like Calcium carbonate, Magnesium carbonate, Lead carbonate, Copper carbonate, Sodium carbonate and Iron carbonate. I also have to take precise and accurate readings. This means to use a measuring cylinder to determine the reading of the hydrochloric acid. Analysis I think that the higher the concentration of hydrochloric acid the faster the carbon dioxide will be given off. I predict that the most or highest metal carbonate will be Copper carbonate (CuC03).

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22. ## titration of limewater

Because there is a 1:2 molar ratio we need to double the concentration of the Calcium Hydroxide to find the concentration of Hydrochloric Acid needed. So: Concentration of HCl = 0.01 x 2 = 0.02 Mol dm-3 The concentration of HCl we are given is 2.00 Mol dm-3. So now we need to find out by how much the acid is too concentrated. 2.00 /0.02 = 100 times too concentrated So the acid needs to be diluted 100 times before using it in the titration.

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23. ## Finding the concentration of a chemical. Outline of procedures: to prepare a standard solution of sodium carbonate and carry out a series of titrations to determine the concentration of hydrochloric acid.

Then I will carefully weigh out the mass of solute, dissolve it into water and transfer the solution into a volumetric flask. This is a flask of known volume. When the level of liquid in the flask reaches the graduation mark on the neck of the flask I will know the volume of the liquid in the flask. I will then add distilled water to top off the solution to the graduation mark. A standard solution can only be made from a pure solid which is stable in air therefore I will have to make a solution of sodium hydroxide and then find its concentration.

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24. ## To Determine the Concentration of a Limewater Solution.

I will round my volume up to 10cm3 and use a pipette to measure the acid out. I will therefore make up a solution of dilute HCl using 450cm3 of distilled water and 10cm3 of 2M HCl. Concentration of HCl in Final 250cm3 solution: Molarity of given acid = 2M Volume of given acid used in solution = 0.01dm3 Volume of final acid solution = 0.5dm3 Concentration of HCl in 10cm3 used = 2 X 0.01 = 0.02moldm-3 Concentration of HCl in final 250cm3 = 0.02/0.5 = 0.04moldm-3 Method for Diluting Acid.

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25. ## concentration of acid rain

When the Na2CO3 reacts with the H2SO4 the CO32- ions react with the H+ to form CO2 and H2O. The carbon dioxide gas will bubble out of the titrated solution, this my distort the solution so it will be harder to see where the end point is. I know that the rough concentration of the acid rain is about 0.01 moles, so by means of a balanced equation I can determine the concentration of sodium hydroxide that would be suitable to titrate.

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