science
Controlled assessment- How concentration affects the rate of reaction between sodium thiosulfate and hydrochloric acid.
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Scientific knowledge
Sodium thiosulfate (Na2S2O3), also spelled sodium thiosulphate, is a colourless crystalline compound that is more familiar as the pentahydrate,Na2S2O3·5H2O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.” Sodium thiosulphate has a melting point of 48 degrees C. It is freely soluble in water. It contains five molecules of water as water crystallization. At 48 degrees C, the sodium thiosulfate melts; at 215 degrees C, it loses all its five molecules of water; and above 220 degrees C, it is converted into sodium tetrasulfide.
The collision theory briefly: For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, surface area, temperature and the addition of catalysts.
Different reactions can happen at different rates. Reactions that occur slowly have a low rate of reaction. Reactions that happen quickly have a high rate of reaction. For example, rusting is a slow reaction: it has a low rate of reaction. Burning and explosions are very fast reactions: they have a high rate of reaction.
Collisions
For a chemical reaction to occur, the reactant particles must collide. But collisions with too little energy do not produce a reaction. The particles must have
SA): Strategy
Scientific knowledge
Sodium thiosulfate (Na2S2O3), also spelled sodium thiosulphate, is a colourless crystalline compound that is more familiar as the pentahydrate,Na2S2O3·5H2O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.” Sodium thiosulphate has a melting point of 48 degrees C. It is freely soluble in water. It contains five molecules of water as water crystallization. At 48 degrees C, the sodium thiosulfate melts; at 215 degrees C, it loses all its five molecules of water; and above 220 degrees C, it is converted into sodium tetrasulfide.
The collision theory briefly: For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, surface area, temperature and the addition of catalysts.
Different reactions can happen at different rates. Reactions that occur slowly have a low rate of reaction. Reactions that happen quickly have a high rate of reaction. For example, rusting is a slow reaction: it has a low rate of reaction. Burning and explosions are very fast reactions: they have a high rate of reaction.
Collisions
For a chemical reaction to occur, the reactant particles must collide. But collisions with too little energy do not produce a reaction. The particles must have