Rates Of Reaction

States that in order for a reaction to occur, particles must collide with each other with enough energy to react.

The minimum amount of energy required for a successful collision to occur

Surface area, volume, catalysts, conc/pressure, temperature

• increasing SA = faster rate • smaller objects have larger SA • there are more exposed particles on the surface of the solid = more frequent collisions • more frequent collisions between particles = faster rate

• higher conc. of solid / higher pressure of gas = faster rate • this is because there are more particles in the same volume • increases frequency of collisions • therefore increases number of successful collisions = faster rate of reaction

• higher temp. = faster rate • high temp. = more kinetic energy • makes particles move around faster • higher frequency of collisions = more successful ones = faster rate

At higher temperatures, more particles will have energy greater than or equal to the activation energy, meaning more successful collisions will occur = faster rate

A chemical substance that increases the rate of reaction by providing an alternate reaction pathway with a lower activation energy. It remains chemically unchanged at the end of the reaction.

• marble chips of large + small size but the same mass are put into separate conical flasks each w/ dilute hydrochloric acid • then time taken for the solution to produce 100cm3 of CO22 is measured for both the large and small marble chips • the smaller ones took the least amt. of time as they had a larger SA:V ratio

Calcium carbonate (CaCO3)

Same setup as the SA version, but the only difference is that the concentration of the hydrochloric acid is changed between 2mol/dm3 to 0.4mol/dm3 in increments of 0.4. The volume of acid remains the same

• sodium thiosulfate and hydrochloric acid are put into a flask inside a water bath with a black cross underneath • then time taken for the solution to go cloudy is measured • temperature of water bath varied between ice cold, room temp, warm and boiling water to see which made solution turn cloudy the quickest • the boiling water one turned cloudy the quickest as high temperature increases rate

Sodium thiosulfate + hydrochloric acid => sodium chloride + sulfur + sulfur dioxide + water

• 4 compounds (copper,copper oxide, manganese oxide and potassium iodide) were placed in hydrogen peroxide to see which one would catalyse its decomposition into water and oxygen • manganese oxide was the catalyst as it made the solution effervesce vigorously and produce heat and steam

Water and oxygen

2H2O2 (l) => 2H2O (l) + O2 (g)

Solution turned black (but this was because CuO is black), small bubbles were produced

Steam was produced, lots of heat and vigorous effervescence

No change

Solution turned yellow, effervescence and heat

Change in amount of product/time or 1/time

Cm3/s

• read off the x axis to see where that specific moment touches the curve • then draw a tangent touching that specific part of the curve • then find the gradient of the tangent using rise/run

At the start, there’s a high concentration of reactant particles. This means that: - more frequent collisions between particles - more frequent collisions = more successful collisions so faster RoR - faster rate = steeper gradient