Chemistry - rates of reaction (The rate and extent of chemical change)

equation for mean rate of reaction

total quantity (g or cm³) / time taken (s)

equation for moles (solid)

mass (g)​ / molar mass (g/mol)

molar volume of gas

24 dm³/mol

equation for moles (gas at room temperature)

volume of gas (dm³)​ / 24 dm³/mol

cm³ → dm³

divide by 1000

what 4 conditions can increase the rate of reaction?

how does higher temperatures increase the rate?

• increase surface area

• high temperature

• high concentration

• high pressure

more kinetic energy is transferred which increases amount of collisions

why do smaller objects such as powders increase the rate of reaction?

have a larger surface area to volume ratio, therefore more collisions take place

collision theory

chemical reactions can only occur when particles collide with enough energy

activation energy

the minimum amount of energy that particles must have to react

catalyst

substances which increase rate of chemical reaction by providing an alternative reaction pathway with a lower activation energy

test for hydrogen

• burn splint

• hold splint above tube until a squeaky pop sound is made

how can the student investigate how the rate of reaction when the concentration of is changed by measuring the volume of gas produced?

• use 50cm³ of 1mol/dm³ hydrochloric acid

• use 3cm magnesium ribbon

• set up a conical flask containing 50cm³ of 1mol/dm³ hydrochloric acid

• have bung and delivery tube attached to gas syringe prepared

• add a 3cm piece of magnesium ribbon

• quickly fit bung on conical flask and start a stopwatch

• record the measurement of gas produced every 10 seconds

• repeat experiment with 2 and 3 mol/dm³ hydrochloric acid

how can the student investigate how the rate of reaction when the concentration of is changed by observing change of colour or turbidity?

• use 10cm³ sodium thiosulfate solution

• use 10cm³ dilute hydrochloric acid

• pour 10cm³ of sodium thiosulfate solution into a conical flask

• measure out 40cm³ water with a measuring cylinder and pour into conical flask

• add 10cm³ dilute hydrochloric acid into conical flask and place it on a black cross and start a stopwatch

• record the time it takes for the cross to disappear

• repeat using other concentrations of sodium thiosulfate