What factors effect the rate of a chemical reaction?

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What factors effect the rate of a chemical reactionIntroductionDuring any chemical reaction the concentrations of the reactants decrease and the concentration of products increase with time. The rate of reaction (reaction velocity) may be defined as the rate of change of concentration of a stated reactant or product. The rate of a reaction is found by measuring the amount of a reactant used up per unit of time or the amount of a product produced per unit of time. A reaction can be made to go faster or slower by changing a number of factors. In order for a reaction to occur it is necessary that: particles must collide with each other and the collision must have enough energy. If this happens the original bonds are broken and new bonds are formed - so that new products are formed. Successful collisions (those with sufficient energy) can be increased (or decreased) by a number of factors.AimI am trying to find out what factors effect the rate of a particular reaction - the reaction between Calcium Carbonate and Hydrochloric acid.Key VariablesThe key variables that I could change are:Surface area of solid - The surface area has an effect on the rate of reaction. If the solid has a large surface area then there are more opportunities for collisions to occur between the solid and liquid. This is because there are more opportunities for collisions to occur. If the surface area is small, collision can only occur with the outer atoms and is therefore limited. The diagram below illustrates this:The temperature of the reaction - When the temperature is low, the particles in the reaction do not have much energy so collision is unlikely to occur. However on heating, particles take in energy causing them to move faster and collide more often. Because the collisions have more energy they are more likely to be successful in breaking and reforming bonds. Therefore the rate of the reaction will increase. When the temperature increases by 10C, the rate of the reaction roughly doubles.Concentration of the reactantsThe more concentrated the solvent, the more particles are present and the greater the chance of a successful collision. In dilute acids, with fewer particles the chance of successful collisions occurring is reduced. Therefore if concentration is increased, the reaction rate also increases. This also applies in reactions between two gasses when increasing the pressure has the same effect as increasing the concentration.Amount of the reactantsIt is important to keep the amount of reactants constant in the experiment because, as the reactant is used up, so the reaction slows down. This means a small amount of solid will have a different reaction time to a large amount. A small amount of solid will have fewer atoms so will be less likely to successfully collide with acid particles. The limiting factor would be the amount of the smaller reactant.Presence of a catalystA catalyst increases the rate of a chemical reaction without itself being used up. Catalysts are usually transition metals. In the presence of a catalyst, less energy is needed by a collision in order to be successful. Therefore there are relatively more successful collisions and so the reaction rate increases.In order to ensure a fair test with reliable results, I will need to keep all variables
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constant apart from the one I am intending testing.The investigationI am going to investigate how a change in temperature will effect the rate of the reaction between calcium carbonate (marble chips) and hydrochloric acid). The word equation for the reaction is:Calcium carbonate + hydrochloric acid À calcium chloride + water + carbon dioxideThe chemical formula for this reaction is as follows:CaCO3(s) + 2HCl(aq)À CaCl2(aq) + H2O + CO2(g)I will collect the carbon dioxide as a measure of the rate of reaction.Prediction:I can predict that there will be a positive correlation between the rate of the reaction and the temperature so ...

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