Gas Equilibriums: examples of Reversible Reactions
Q1. Identify the general chemical and physical characteristics of gas equilibriums as a group. Explain the forward and reverse reaction mechanisms. Use nitrogen dioxide and hydrogen iodide as examples and explain how equilibrium is reached.
The general chemical characteristic of gas equilibriums is when the concentrations of reactants and products do not change with time. This is known as the state of reversible reaction. At this state, pressure, density, colour and concentration can be recognised. At equilibrium, both the forward and backward reactions are still continuing because the rates of the forward and backward reactions are equal. This leads to the general physical characteristic of gas equilibriums which is the concentration of each substances become constant and the system is said to be at dynamic equilibrium. The equilibrium can be established in physical equilibrium and in chemical equilibrium.
A reversible reaction that takes place in both the forward and backward directions can be demonstrated by the reaction between gaseous hydrogen and iodine vapours to give gaseous hydrogen iodide:
The physical characteristic for this reaction is that the colour changes from purple to colourless.
Another example would be the reaction gaseous dinitrogen tetroxide vapours to give gaseous nitrogen dioxide is a reversible reaction and may be expressed as:
N2O4 (g) 2NO2 (g)
At equilibrium, the rate of decomposition of N2O4 is equal to the rate of combination of NO2. As the NO2 increases, then it starts declining as NO2 starts combining to form N2O4. This is called reverse reaction. The physical characteristic for this reaction is that the colour changes from colourless, d...
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...this system is increased or decreased, then the time taken to reach equilibrium will not be effected after it was in equilibrium stage.
3. When the volume changes were made and the reaction restarted, the reaction rates were affected. This is because in a low pressure system, the rate of the reaction would be slower because of the space between the particles being bigger and as a result of this, time between collisions (necessary for reactions) also increases.
4. The reason why the position of the equilibrium was unaffected in this reaction because of reaction:
1 mole + 1 mole 2 moles
If the volume is changed, then it will have an equal effect on the concentration of reactants and of products. This is because there are an equal number of moles of gaseous substances on both sides of the arrow. Therefore, the position of the equilibrium was unaffected.
Felder, M. Richard, Elementary Principles of Chemical Processes, 3rd ed.; Wiley: New Jersey, 2000; p 631.
The rate law determines how the speed of a reaction occurs, thus allowing the study of the overall mechanism formation in reactions. In the general form of the rate law, it is A + B C or r=k[A]x[B]y. The rate of reaction can be affected by the concentrations such as A and B in the previous equation, order of reactions, and the rate constant with each species in an overall chemical reaction. As a result, the rate law must be determined experimentally. In general, in a multi-step reaction, there will be one reaction that is slower than the others.
anyway) Note these factors affect the rate of the reaction, but not the final. amount of carbon dioxide produced). Why these factors affect it: higher temperature makes atoms move more. so they are more likely to bump into each other and react.
will result in an increase in the speed of the rate of reaction it has
The Equation Of State These three gas laws that were proposed by Boyle, Amontons and Charles can be summarised as follows: For a fixed mass of gas pV = constant if T = constant (i) p/T = constant if V = constant (ii) V/T = constant if p = constant (iii)
Abstract: This week we experimentally determined the rate constant k for the reaction 2HCl (aq) +Na2S2O3 (aq) → S (s) + SO2 (aq) + H2O (l) + 2NaCl (aq). In order to do this the average reaction time was recorded in seconds during two trials. The data from the experiment shows this reaction is in the first order overall: rate=.47s-1 [HCl]0 [Na2S2O3]1. These findings seem to be consistent with the expected results
The aim of this experiment was to investigate the affect of the use of a catalyst and temperature on the rate of reaction while keeping all the other factors that affect the reaction rate constant.
This law also relates itself to Thermodynamics, stating that "at constant temperature the internal energy of an ideal gas is independent of volume."1
t = time, a = volume of reactant, k is a constant of proportionality; x is the order of reaction. Because k is a constant of proportionality 1/t is directly proportional to the rate of reactant. Then to find out the order of reaction in a catalysed system the volume of ammonia molbydate is varied and the concentration of the other reactants kept the same. Thirdly to investigate the activation energies, the concentrations are kept the same and the temperature is varied.
If I were to roughly plot a graph for the reaction, it would look like
5. In a gas increasing the pressure means molecules are more squashed up together, so there will be more collisions. My Investigation. I am going to investigate the concentration variable. I have chosen this because in my opinion it will be the easiest one to measure.
Many factors influence rates of chemical reactions. Some of these factors include: the nature of reactants, for example the formation of salts, acid-base reactions, and exchange of ions are fast reactions, while in reactions where bigger molecules are formed or break apart are typically slow; temperature, frequently, the higher the temperature, the faster the reaction; concentration effect, the reliance of reaction rates on concentrations are called rate laws. Rate laws are expressions of rates in terms of the concentra...
This form of chemical reaction is known as a single displacement reaction and is exothermic. The reaction is irreversible and is written as:
Since the days of Aristotle, all substances have been classified into one of three physical states. A substance having a fixed volume and shape is a solid. A substance, which has a fixed volume but not a fixed shape, is a liquid; liquids assume the shape of their container but do not necessarily fill it. A substance having neither a fixed shape nor a fixed volume is a gas; gases assume both the shape and the volume of their container. The structures of gases, and their behavior, are simpler than the structures and behavior of the two condensed phases, the solids and the liquids
The time taken for this to happen is the measure of the rate of reaction. We must do this several times, and change the concentration of sodium thiosulphate. The rate of reaction is a measure of the change, which happens during a reaction in a single unit of time. The things that affect the rate of reaction are as follows. Surface area of the reactants Concentration of the reactants