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Planning experimental procedures.

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Skill Area P : Planning experimental procedures: Information: Word equation: Hydrochloric acid (s) + Calcium carbonate (aq) ==> Carbon dioxide (g) + Calcium Chloride (aq) + Water (l) Chemical equation: 2HCl (s) + CaCO3 (aq) ==> CO2 (g) + CaCl2 (aq) + H2O (l) Ratio: 2 : 1 ==> 1 : 1 : 1 Molar ratio in thousandths: 0.002 : 0.001 ==> 0.001 : 0.001 : 0.001 The above equation shows when two moles of hydrochloric acid are added to one mole of calcium carbonate the products made are one mole of carbon dioxide, one mole of calcium chloride and one mole of water. Introduction: In a chemical reaction, the starting materials are called the reactants, and the finishing materials are called the products. If the reactants take a short time to change into products the reaction is a fast reaction. If the reaction takes a long time to change into the products the reaction is a slow reaction. The factors which can alter the reaction are: * Temperature because as the temperature is increased, the ions in the reactants gain more kinetic energy, and so move faster leading to a higher rate of reaction. Thus, there is a greater frequency of collisions and with a greater force i.e. they move more vigorously. So, there is a greater chance the reactants will react and they will then react faster. * Concentration of the reactants because if you increase the concentration of the reactants, there would be more molecules in the same volume and so the molecules would collide more often. So, the energy of the collisions will remain the same (as long as the temperature is kept constant), but the molecules will collide more often (as there are more of them) and so there is a greater chance of them reacting. Therefore increasing the concentration of the reactants would increase the rate of reaction. ...read more.


? 1 moles / dm3 Volume ( litres ) 0f HCl = 0.002 Moles 1 mole / dm3 Skill Area P : Planning experimental procedures Volume ( litres ) of HCl = 0.002 litres = 2 cm3 However I shall multiply the volume of hydrochloric acid by four to create 8 cm3 instead of 2 cm3 which as it is an easier amount to use. I had to find the volume of carbon dioxide evolved from reacting calcium carbonate and hydrochloric acid .To make 8cm3 for a 0.5 Molar solution of Hydrochloric acid this formula is used: No moles of Hydrochloric acid = Volume ( litres ) ? Concentration ( moles / dm3 ) No moles of Hydrochloric acid = 0.008 litres ? 0.5 moles / dm3 No moles of Hydrochloric acid = 0.004 Moles The ratio of the reactants and products is seen below in the equation: Chemical equation: CaCO3 + 2HCl (s) ==> CO2 (g) + CaCl2 (aq) + H2O (l) Ratio: 1 : 2 ==> 1 : 1 : 1 Molar ratio in thousandths: 0.002 : 0.004 ==> 0.002 : 0.002 : 0.002 The molar ratio in thousandths highlighted in red is the ratio which is needed. It shows when 0.004 Moles of Hydrochloric acid is used 0.002 Moles of Carbon dioxide is evolved. At room temperature and pressure ( RTP ) one mole of any gas will have a volume of 24 dm3 ( 1dm3 = 1 litre = 1000 cm3 ) and the following formula is used: Volume of CO2 = Moles of gas ? 24,000 cm3 Volume of CO2 = 0.002 ? 24,000 cm3 Volume of CO2 = 48 cm3 Therefore the amount of carbon dioxide evolved is 48cm3 when 8cm3 of 0.5 Molar hydrochloric acid is used. To make 8cm3 for a 1.0 Molar solution of Hydrochloric acid this formula is used: No moles of Hydrochloric acid = Volume ( litres ) ...read more.


This prevented it reacting with the hydrochloric acid as well as it should have, and so lowered the rate of reaction. * although the chips had the same mass, they had different surface area. This did not make the investigation a fair test, as those chips with a greater surface area had a higher rate of reaction, and those chips with a lower surface area had a lower rate of reaction. * I could only measure the gas syringe to the nearest cm3 and I found this to be not a very high accuracy. This limited the accuracy of my results. * the room temperature may not have been constant, causing the particles in the hydrochloric acid to have different kinetic energy, causing different rates. * Not every single drop of the hydrochloric acid or the distilled water could be removed from the measuring cylinders, and some of it remained in the measuring cylinder. * It was difficult to simultaneously look at the stop-watch to see the time and look at the gas syringe to see the volume of gas released. Time was wasted in reaction time and this would have affected the results slightly. Further Improvements * more duplicates could have been taken, so that my results would be more reliable. * a burette could have been used to measure out the hydrochloric acid and the distilled water. * more concentrations could have been used. By taking more concentrations, I would have more points on my final graph, leading to a greater accuracy. * the room temperature could be measured every 15 minutes while doing the experiments to make sure that it does not vary too much. this is a test area 19/3/2001 we are looking to see if the computer crashes, if so how long it takes it has now been on for half an hour and it is working very well 2.00pm started- time time now 2.30pm time now 2.45pm timre 3.00pm why is it not crashng, what is the matter time now is 3.15pm I am going to switch off and start again. restarted 3.30pm ...read more.

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