Introduction: The experiment taking place is between calcium carbonate [CaCO3] and hydrochloric acid [HCl]. Calcium carbonate, also known as marble, is a metamorphic rock. This is a rock that is formed over long periods of time under high temperature and pressure. It is also formed when carbon dioxide reacts with calcium hydroxide to produce calcium carbonate. Calcium hydroxide + carbon dioxide calcium carbonate + Water Ca(OH)2(aq) + CO2(g) CaCO3(s) H2O(l) When an acid reacts with a carbonate the products are salt, water and carbon dioxide gas.
When hydrochloric acid reacts with calcium carbonate the products are calcium chloride, water, and carbon dioxide. The formula for this reaction is: Hydrochloric acid + Calcium carbonate Calcium chloride + Water + Carbon dioxide HCl(aq) + CaCO3(s) CaCl2(aq) + H2O(l) CO2 As you can see above, in the reaction, the reactants are hydrochloric acid and calcium carbonate, and the products are calcium chloride, a salt, water and carbon dioxide. The speed at which the reactants will create the products is called the rate of reaction. This follows a theory called the kinetic theory.
This theory states that all states of matter contain particles, which are constantly moving/vibrating [kinetic energy]. In solids the particles are positioned close together which allows them to vibrate slightly. Between them are strong bonds that hold them together in a fixed place. The particles present in liquid have further distance between them; therefore the forces of attraction are less than in solids. The particles have weaker bonds that allow them to move. The particles in a gas are much further apart than in a solid or liquid, and have very weak bonds that allow them to move quite freely.
There are virtually nil forces of attraction between the gas particles. This therefore means that solids would have the slowest rate of reactivity, liquids would me in the middle, and gasses would have the fastest rates of reaction. The factors that would affect the rate of reaction would be: Concentration of hydrochloric acid. The higher the concentration of the acid the faster the rate of reaction will be. This is because there would be more particles of hydrochloric acid present in the reaction; therefore there would be more collisions, which would therefore results in a faster rate of reaction.
The following diagram can show this overleaf: As you can see, in the low concentration of hydrochloric acid, there are 5 particles present, compared to 8 particles of calcium carbonate. In the higher concentration however, there are 10 particles of hydrochloric acid present, and the same amount of calcium carbonate particles present. This should therefore double the rate at which carbon dioxide is produced as there is now double the amount of collisions occurring. Catalyst catalysts are useful in a reaction as it speeds up the rate of reaction without being used up.
Most catalysts are there to speed up the rate of reaction, however some can slow them down. The ones that speed up the rate of reaction are called activators, and those that slow down the rate of reaction are called inhibitors. For example, in the reaction where the enzyme (biological catalyst) breaks down hydrogen peroxide (H2O2) into water (H2O2) and oxygen (O2), glycerine is sometimes added, this is in order to slow down the rate at which hydrogen peroxide is broken down during storage. Most of the catalysts that are used are transition metals and their compounds, such as the making of margarine, where a nickel catalyst is used.
The nickel catalyses an addition reaction, between a double bonded hydrocarbon (alkenes), the oil, and hydrogen. The result is a solid fatty product, which is margarine. By controlling the rate of reaction (i. e. how much catalyst is used) you can also control the solidity of the margarine. A catalyst allows a substance to react more easily by reducing the activation energy. This is where the energy needed in order to break the bonds is reduced. Therefore the particles require less energy to react, and the reaction occurs faster.
Catalysts can be compared to getting from a-b in a car. The normal way would be by going through small roads, however using the motorway is like using a catalyst. This is as it takes less energy (petrol) to get there as well as far less time than compared to taking the smaller roads. Temperature when particle collide with each other, they do not always react. This is, as they do not have the sufficient kinetic energy for them in order to stretch or beak the bonds in order to form the products. In some reactions, only the particles with high energy can react.
This sort of situation can be compared to a car crash; if two cars hit each other at low speeds, then hardly any damage will be done, however, if the cars hit each other at a higher speed, then a lot more damage would be done to both cars. Mass of calcium carbonate chips when you increase the mass of the chips, it means that there are more particles present for the hydrochloric acid to collide with. This would cause more collisions, which means a faster rate of reaction. Surface area of calcium carbonate chips in a reaction; if one of the reactants is a solid then the surface area of the solid will affect the rate of reaction.
This is because the only particles that can collide with each other are the ones at the solid-liquid interface. This is the area in which the surfaces of the marble chips come in contact with the hydrochloric acid. This would therefore mean that the larger the surface area of the marble chips, the more collisions there would be, which a higher rate of reaction is. Diagram A and B are marble chips with the same masses. Diagram be has a higher surface area, and as you can see, there are more marble particles exposed to the surrounding, which would mean that there would be a larger amount of collisions in a given amount of time.