6 Market Asnwers

Question 1

Nitrogen molecules and oxygen molecules react exiremely slowly, even at 200°c.
- The reaction between nitrogen and oxygen becomes faster as both the temperature and the pressure increase.
— Explain why, using the reacting particle model.

Answer 1

—> there are strong bonds between the oxygen and nitrogen molecules, meaning that high energy is needed to break them
—> more energy is needed for them to react
—> in the particle model, gases are very spread apart meaning that they don’t collide often
—> increasing the pressure means that the particles are closer together, increasing the amount of collisions per second
—> an increase in the temperature means that the molecules gain more energy and are able,to move around faster
—> this means that more successful collisions are able to take place per second

Question 2

Potassium chloride is a mineral found in many foods.
A student wants to make a salt called potassium chloride, KCl, by neutralisation of an acid by an alkali.
Describe how to make a pure, dry sample of potassium chloride in a laboratory by neutralisation.

Answer 2

-> acid used is HCl
-> alkali used is potassium hydroxide/oxide
-> while they react gently heat them
-> use a pH Probe to check the pH
-> when the pH is near neutral, remove the potassium hydroxide to prevent contamination
-> evaporate the water
-> let the salt dry in the oven

Question 3

In questions about producing a salt containing ammonium what is the process

Answer 3

-> TITRE the acid against alkali using indicator to provide exact values
-> use those values again to conduct the reaction but without the indicator so that it does not contaminate it
-> heat them whilst reacting
-> once a solution containing water is produced evaporate most of the water leaving some behind
-> leave to dry in an oven overnight to crystallise and form ammonim salt