6. Chemical Reactions
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Equilibrium
The state achieved when the forward and reverse reactions occur at the same rate and the concentration of the reactants and products stay constant.
Is White copper sulfate powder turning blue when water is added and white again when water is evaporated a chemical or physical reaction
Physical
How can compounds be split up
chemical separating techniques such as electrolysis
Difference between chemical and physical changes
In a physical reaction, the substance itself doesn’t change, only the form. E.g. changes of state In a chemical reaction reactants are converted to products and have different properties Physical changes are reversible, most chemical changes aren’t e.g. combustion
What factors affect the rate of reaction (5)
Concentration Pressure (only in gases) Temperature Catalyst Surface area
rate of reaction
The change in concentration per unit time of either the product or the reactants
What is the formula for gases
v=n24
How does concentration affect the rate of reaction
The higher the concentration the higher the number of particles per unit volume, resulting in more effective collisions per unit time and a faster reaction rate
How does temperature affect the rate of reaction
As the temperature increases, the particles gain energy and move faster, resulting in more effective collisions per second with sufficient energy to react
How does a catalyst affect the rate of reaction
By introducing a catalyst it lowers the activation energy resulting in a higher rate of effective collisions per second as more molecules collide with equal or greater activation energy.
How does surface area affect the rate of a reaction
The smaller the particles size(the greater the surface area), the more surface exposed for reactions to take place, therefore there are more effective collisions per unit time.
How does pressure affect the rate of reaction
Reducing the volume of the container means that you are reducing the space in which the gas particles can move, therefore more effective collisions per unit time.
How can we measure the rate of a reaction
• Measuring the volume of gas given off every minute • Measure the decrease in mass as the gas escapes
How is nitrogen obtained
Distillation of liquid air
How is hydrogen obtained
Methane
What effect does equilibrium have on the concentration of the reactants/products in a reaction
None, they cancel each other out
Homogeneous equilibrium
One in which all species present are in the same phase E.g gas-phase/solution reactions
Heterogeneous equilibrium
One in which the reactants, products, or both are in more than one phase E.g reactions involving solids and gases or solids and liquids
What are the characteristics/requirements of equilibrium
Constant concentration of reactants and products given there is no other change in the system Dynamic-products and reactants changing into each other by chemical reactions constantly and at the same time Must occur in a closed system so nothing can escape
How does a catalyst effect equilibrium
It affects the rate of a reaction, but has no influence on the equilibrium of a reaction
What factors affect equilibrium (3)
Temperature Pressure (only in gasses) Concentration
What is the Haber process
The industrial process used to make ammonia
What are the uses of ammonia
Nitric acid-cleaning products Explosives Fertilizers
How is nitrogen gas obtained
From fractional distillation