2.3 Rates Of Reaction

Measuring the loss of a reactant or gain of a product over time

1 / time

Gas volume, change in mass, formation of a precipitate

The reactants are mixed together in a conical flask, the gas syringe is connected and the stop clock is started, and the scale on the gas syringe is used to record volume of gas at regular intervals A thistle funnel can be used to add the solid to the reaction mixture. It must be below the level of the reaction mixture to prevent gas escaping. This way all gas travels to the delivery tube is measured

Reactants are mixed together, initial mass is measured and stop clock is started, and the mass of the reacting mixture is measured at regular time intervals The cotton wool prevents any loss of liquid from the conical flask caused by liquid spray

The reactants are mixed and a stop clock is started, the stop clock is stopped when the X is no longer visible when viewed from above

Acid + metal = salt + hydrogen Measure gas volume or change in mass

Acid + calcium carbonate = calcium salt + water + carbon dioxide Measure gas volume or change in mass

Hydrogen peroxide = water + oxygen Measure gas volume or change in mass

Hydrochloric acid + sodium thiosulfate with= sodium chloride + sulfur dioxide + sulfur + water Measure gas volume or change in mass or formation or precipitate

X axis

Thing you change (usually time in this topic)

Thing you measure (mass/gas volume in this topic)

When reacting atoms, molecules or ions collide with enough energy to react

The minimum amount of energy for a collision to be successful

How many successful collisions (of particles) occur

• at a low temp the particles collide with energy less than the activation energy - many collisions are unsuccessful • at a high temp the particles have more energy equal to or greater than the activation energy • therefore they move more quickly and collide more often leading to more successful collisions per unit time • rate of reaction is increased

• at a low concentration there are fewer particles and therefore few successful collisions • at a high concentration there are more reactant particles in the same volume • therefore they collide more often leading to more successful collisions per unit time • rate of reaction is increased

• a large piece of solid has a small surface area and only a few particles can react • if the solid is broken down into small pieces it has a large surface area and more particles are exposed to the other reactant • therefore they collide more often leading to more successful collisions per unit time • rate of reaction is increased

A substance which increases the rate of a reaction without being used up

Transition metals and their compounds eg manganese (iv) oxide in the catalytic decomposition of hydrogen peroxide and iron

• for a reaction to occur, particles must collide with sufficient energy to overcome the activation energy • catalysts increase this rate of reaction by providing an alternative reaction pathway and lowering the activation energy • this means there are more successful collisions per unit time • the rate or reaction increases