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The rate of reaction of sodium thiosulpahte and acid.

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Chemistry coursework: Plan Scenario When sodium thiosulphate reacts with an acid, a precipitate of sulphur forms. I am investigating one of the factors affecting the rate of reaction between sodium thiosulpate and hydrochloric acid. In this case I will investigate the concentration. Hypothesis The rate of reaction should vary as different amounts of sodium thiosulpahte and acid is added. I think that increasing the concentration of reactants will increase the speed of the reaction. Equation for the Reaction Na S O + 2HCl-->2NaCl +S+H O+SO Background Information Concentration Foe chemicals in solution, the concentration can be the number of grams of solute per litre of solution. For a reactant chemical, which is a gas, the concentration means the pressure of the gas. So increasing the pressure of reactant chemicals, which are gases, increases the rate of reaction. For example, in a dilute acid solution here are not so many acid particles. This means that there is little chance of an acid particle colliding with particles in it; therefore there will be a greater chance of successful collision between acid particles and other particles. ...read more.


Adding a Catalyst Some reactions can be speeded up, by using a catalyst. This happens because, in the presence of a catalyst, a collision needs less energy in order to be successful. This means that more collisions become successful during any period of time, goes faster. Light Light is a form of energy, and it has a particular range of wavelengths. For some reactions, the reactants are able to absorb the amount of energy in light and then use this as the energy they need to react. Most chemicals cannot dot his and so the absence or presence of light does not affect the sped at which they react. The formation of silver salts takes place when a photographic film is exposed to light. Photosynthesis, the reaction by which green plants synthesis sugars, takes place in sunlight. Variables Variables are factors, which could affect the investigation, these are: Time Rate of Reaction Temperature Volume Mass Independent Variables The independent variable through out the investigation is the concentration of sodium thiosulphate solution as this will be what is changed throughout the investigation. ...read more.


I will then add the acid to the flask and start a stop clock. I will swirl the flask to mix the solution and put it on a piece of paper marked with a cross. I will look down on the cross from above and when the cross disappears I will stop the clock and note the time. I will then repeat these using different concentrations of sodium thiosulphate. I will make up 50cm3 of each solution by mixing different volumes of the original sodium thiosulphate solution with water. Safety Precautions * Wear safety goggles to protect your eyes * Wear an apron to protect clothing * Tie hair back so it doesn't get tangled in anything * Don't spill any hydrochloric acid on skin, as it is highly corrosive. * Asthmatics should not inhale as it gives off sulphur dioxide, which is highly toxic. Apparatus Conical flask Small cylinder Stop clock Paper marked with a cross 250cm3 beaker Reliability To make sure that my results are accurate and precise, I am going to repeat my experiment and for reliability so I will have two sets of results. ...read more.

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