OCR Gateway GCSE Chemistry A Monitoring and controlling chemical reactions (C5) overview quiz quiz

The particles must be exactly the same size as each other and collide very slowly

The particles must be both hot and large, and they must collide head-on with one another

The particles must collide gently many times over until they finally stick together

The particles must collide and the collision must have at least the activation energy

Particles move faster so collide more often, and more collisions have enough energy to react

Particles get bigger as they warm up, so they end up colliding far less often than before they did

The activation energy of the reaction falls and at the same time the particles all shrink

More product is made straight away and the pressure inside the container rises sharply

The powder is much more concentrated than the large lumps of the solid

The powder has a larger surface area, so collisions are more frequent

The powder has a higher activation energy than the large lumps do

More product is made overall from the powder than from the lumps

0.5 cm3/s

30 cm3/s

2.0 cm3/s

1800 cm3/s

Read off the volume of gas shown on the curve at that time

Divide the final volume of gas by the total amount of time taken overall

Measure the whole area underneath the curve up to that point

Draw a tangent to the curve at that point and find its gradient

40 g/dm3

10 g/dm3

0.04 g/dm3

1000 g/dm3

Universal indicator is far too expensive to use in a titration

A single indicator gives a sharp colour change at the end point

Universal indicator reacts with the acid and uses some of it up

A single indicator changes through many colours as you add acid

The forward and the backward reactions have both completely stopped happening in the system

Only the forward reaction is still happening, while the backward reaction has stopped entirely

The forward and backward reactions happen at the same rate, so concentrations stay constant

All of the reactants have now turned into products and nothing is left to react any further

The yield increases

The yield stays exactly the same

The reaction stops

The yield decreases

There are fewer gas moles on the right, so increasing pressure shifts the equilibrium to that side

There are more gas moles on the right, so increasing the pressure shifts the equilibrium to the right

Pressure has no effect at all on a reaction at equilibrium when all of the substances are gases

The iron catalyst becomes far more effective at high pressure, so it makes much more ammonia

It lowers the overall energy of the reactants so that they need much less energy to start reacting together

It provides an alternative pathway with a lower activation energy, so more collisions are successful

It is gradually used up during the reaction, releasing energy that speeds the reaction up

It increases the activation energy so that the reactant particles collide far harder together

They are metals that melt very easily when they are gently warmed up

They are used up very quickly whenever the temperature is kept low

They are proteins that denature (change shape) if the temperature is too high

They are only ever able to work properly in complete darkness with no light at all