Rate of Reaction Flashcards
What happens in a chemical reaction?
In a chemical reaction old bonds are broken and new bonds are formed, to make a new substance or product. During this process there is a rearrangement in the electrons in the valence shell (chemical reaction).
How do we know a reaction is occurring?
- There could be a change in colour
- Change in temperature due to energy being given off or absorbed, ones receiving energy are endothermic, ones giving away energy are exothermic
- There might be fizzing
- It might form an insoluble solid, precipitate
- One or more of reactant getting used up or disappearing
Collision Theory
For a reaction to take place the particles must collide. Not all collisions will result in reactions taking place. The collision must be effective in order for reactions to take place. For collisions to be effective the collision must be energetic (move faster to have more kinetic energy). The energy does not guarantee they will collide, so they need to have correct orientation.
3 things you need for a successful collision
- The particles must collide
- Energy (move faster so more kinetic energy)
- Correct orientation
What is rate of reaction?
Reaction rate is a measure of how fast a reaction is occurring.
Rate of chemical reaction is a measure of the number of “effective” collisions occurring per units time. In other words, reaction rates is a measure of the frequency of collision between the particles of the reactants. The greater the frequency of collisions the greater the reaction rate.
Frequency
Number of effective collisions per units time.
3 ways to measure the rate of reaction.
- How many bubbles are being given out every 10 seconds (not good one)
- Time how long it takes when the reaction is complete
- You can measure the mass of the products
Factors that determine the rate of reaction.
Temperature, concentration, surface area and catalyst.
How does the temperature affect the rate of reaction?
Rate of reaction depends on the number of effective collisions per unit time. Temperature is the measure of average kinetic energy of particles. As the temperature increases, the average kinetic energy of particles increases so they start to move faster. Since the particles are now moving faster, there will be a lot more collisions per unit time. Also, these colliding particles have greater energy so there will be a greater number of effective collisions per unit time, causing the rate of reaction to increase.
Discuss why reaction between HCl and powdered since is much faster than between same HCl and zinc granites.
Powdered zinc has larger surface area compared to zinc granites. Reaction only occurs when reactant particles collide. Only those zinc particles are exposed to acid particles that are on the surface. So having larger surface area means there are greater number of particles that can collide. The greater the number of collisions per unit time the greater the reaction rate. This is why reaction between powdered zinc and HCl is faster than between HCl and zinc granite.
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Discuss how concentration of acid effects the rate of reaction between HCl and zinc granules?
Concentration of a solution is a measure of the number of solute particles per unit volume. Acid with higher concentration will have a greater number of particles per unit volume. Reaction rate is determined by the number of effective collisions between HCl particles and zinc particles. With greater concentration of acid there will be a lot more particles per unit volume that can collide. This means there will be a lot more effective collisions between acid and zinc particles per unit time when the acid concentration is higher. The greater the number of collisions the greater the number of effective collisions per unit time the greater the rate of reaction.
When does reaction stop?
When one of the reactants have been used up.
Qualitative data
Information that is not in numerical form, like open ended questions and unstructured observations.
Quantitative data
Quantitative research gathers data in numerical form which can be put into categories, or in rank order, or measured in units of measurement. This type of data can be used to construct graphs and tables of raw data.
