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Chemistry - Acids and bases - Rates of reaction
Terms in this set (5)
Calcium carbonate (marble chips) and hydrochloric acid react together in conical flask.
Calcium carbonate + hydrochloric acid ---> Calcium chloride + water + carbon dioxide gas
- Describe an observation you would make when this reaction occurs
Bubbles are produced, Calcium carbonate fizzes/dissolves
The mass of the flask and contents is measured on a scale overtime and recorded on a graph.
Mass of flask and contents decreases over time
Explain why the mass decreases with time
- Consider all the products being formed
- Explain what is happening, in term of particles AND the rate reaction, in each section of the graph
The mass decreases with time because : the amount of reactant particles decrease overt time as they are colliding and forming products of calcium chloride, water and carbon dioxide. One of the products is a gas, carbon dioxide, which is released into the atmosphere, so the mass decreases as carbon dioxide is given off.
Section X: The rate of reaction is very fast because lots of calcium carbonate and hydrochloric acid particles are colliding and forming products per second. One of which is carbon dioxide. So lots of carbon dioxide is released into the atmosphere per second, therefore the mass is decreases quickly
Section Y: The rate of reaction is slowing down because there are less calcium carbonate particles and hydrochloric acid particles present so there are less collisions occurring per second so less carbon dioxide is produced per second. Therefore little mass is lost as little carbon dioxide is produced.
Section Z: The reactions has stopped as there are no more calcium carbonate particles left to react with the hydrochloric acid particles, therefore no carbon dioxide is produced so no mass is lost and the mass isn't decreasing anymore
When more concentrated hydrochloric acid is used, the reaction is faster.
Explain the difference in the rate of reaction
- Refer to the particles, collisions and rate of reaction
A higher concentration of hydrochloric acid means more hydrochloric acid particles are present in the solution in a given volume. A high concentration of hydrochloric acid means, more hydrochloric acid particles are available to collide with calcium carbonate particles so there are more collision between calcium carbonate and hydrochloric acid particles, so more successful collisions occur per second. Since more particles are colliding per second, the rate at which the reaction is occurring is greater, so the reaction rate increases.
The following experiment was carried out at 20°C and 40°C. Marble chips (calcium carbonate) were added to hydrochloric acid in a conical flask. The mass and size of the marble chips, and the concentration and volume of hydrochloric acid used, were the same for both experiments. The flask was connected to an inverted measuring cylinder in a basin of water.
The volume of gas produced at two different temperature was measured for a few minutes and the results were used to sketch a graph.
Line B has a steeper gradient at the start and the volume of gas produced stops faster than Line A, which has a less steep gradient at the start than Line B and finishes slower.
State which line on the graph represents the reaction at 40°C and explain how you worked this out
- Identify which line represents the reaction at 40°C
- Explain why the line you have identified is the reaction at 40°C
- Give reasons for the different rates of reaction in terms of particles
- Explain why both lines end up horizontal
Line B represents the reaction at 40°C. You can tell this because the the line is steeper than line A at the start which shows a great amount of gas has been produced in a short amount of time. The reason the reaction of the experiment when carried out at 40°C is quicker than the experiment when carried out at 20°C is because when the temperature increases the particles gain kinetic energy and move faster therefore they collide more often. Since the particles have more energy it is more likely that the collisions will have enough energy to result in a reaction. This means increasing the temperature results in both an increase in the frequency of collisions and more importantly in the effectiveness of the collisions so that there is a greater chance that the collisions between particles will overcome the activation energy barrier. Both lines end up horizontal because this is when both reactions have finished as the reactants have been completely used up and therefore no more gas can be produced. Both finished with the same amount of gas produced as they started with the same amount of reactants.
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