Rates of reaction

Question 1

A reaction needs

Answer 1

Particles must collide with enough energy in order to react

collision frequency of reacting particle

Energy transferred per collision (needs to be the minimum energy activation energy to react and break bonds

Question 2

Factors affecting rates of reaction

Answer 2

temperature, concentration of solution or pressure of gas , surface area (solid)
, presence of catalyst

Question 3

How does temperature increase rate of reaction

Answer 3

If the temperature is increased, the particles have more energy and so move quicker. Increasing the temperature increases the rate of reaction because the particles collide more often and with more energy.

The higher the temperature, the faster the rate of a reaction will be.

Question 4

Increasing concentration or pressure

Answer 4

If the concentration of reactants is increased, there are more reactant particles moving together. There will be more collisions and so the reaction rate is increased. The higher the concentration of reactants, the faster the rate of a reaction will be.

same with pressure increased pressure more gas particles occupies smaller space

Question 5

Surface area

Answer 5

By decreasing the particle size of a reactant, we are increasing its surface area. The greater the surface area, the higher the chance of collisions, thus the faster the rate of reaction. The smaller the particle size the faster the reaction.

Question 6

Catalyst

Answer 6

A catalyst provides an alternative reaction pathway that has a lower activation energy than the uncatalyzed reaction. This does not change the frequency of collisions. However, it does increase the frequency of successful collisions because a greater proportion of collisions now exceeds this lower activation energy.

LEARN GRAPHS

Question 7

Calculating rate of reaction formula

Answer 7

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​Rate​ ​of​ ​reaction​ ​=​ ​amount​ ​of​ ​reactant​ ​used divide
​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​Time
​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​Rate​ ​of​ ​reaction​ ​=​ ​amount​ ​of​ ​product​ ​formed divide
​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​Time
o Quantity of reactant or product can be measured by the mass in grams or
by a volume in cm3

o Units of rate of reaction may be given as g/s or cm3/s

o You​ ​can​ ​also​ ​use​ ​quantity​ ​of​ ​reactants​ ​in​ ​terms​ ​of​ ​moles​ ​(instead​ ​of
mass​ ​or​ ​volume)​ ​and​ ​therefore,​ ​units​ ​for​ ​rate​ ​of​ ​reaction​ ​in​ ​mol/s

Question 8

Rate of reaction graphically

Answer 8

To measure the rate of reaction: draw tangents to curves and use the
slope of the tangent

Calculate​ ​the​ ​gradient​ ​of​ ​a​ ​tangent​ ​to​ ​the​ ​curve​ ​on​ ​these​ ​graphs​ ​as​ ​a
measure​ ​of​ ​rate​ ​of​ ​reaction​ ​at​ ​a​ ​specific​ ​time

Question 9

Precipitation and colour change

Answer 9

1. You can record visual change in a reaction if the initial solution is transparent and product is a precipitate which clouds solution(becomes opaque)
2. You can observe a mark through the solution and measure how long it takes to disappear - faster mark disappears , quicker the reaction

3.If reactants are coloured and the products are colourless(vice versa) you can time how long it takes for the solution to gain or lose colour.

4.Results are very subjective - different people may disagree when the mark ‘disappears or solution changes colour.

You cant plot a rate of reaction graph with this experiment

Question 10

Change in mass (usually gas given off)

Answer 10

1. Measuring the speed of a reaction that produces a gas can be carried out using a measure balance

2.As the gas is realeased , the mass dissappearing is measured on the balanced

3.The quicker the reading on the balance drops the quicker the reaction

4. If you take measurements at regular intervals you can plot a rate of reaction graph and find the rate quite easy.

This is the most accurate of the three methods because balance is very accurate. Disadvantage is gas released straight in the room