Principles Of Chemistry

Question 1

Dilution practice

Answer 1

Dissolving potassium manganite in water demonstrates how slow diffusion in liquids is be as use of the small amount of gaps in the liquids that other particles can pass into

The random movement of particles causes the purple colour to spread out evenly throughout the water

Adding more water will cause the potassium manganite particles to spread out further and results in a more dilute, less purple liquid

Question 2

Diffusion experiment

Answer 2

In one end of a tube place a pad soaked in ammonia and in the other a pad soaked in HC

Wait for around 5-10 mins until a white ring of ammonium chloride forms somewhere in the tube

The white ring of ammonium chloride forms closer to the HCL be sure ammonia particles are lighter and therefore travel (diffuse) faster.

It still takes up to 5 mins for ring to form because particles move randomly and collide with the air particles in the tube

Question 3

What is meant by solvent

Answer 3

The liquid in which the solid dissolves in

Question 4

What is meant by solute

Answer 4

The substance that dissolves

Question 5

What is meant by solution

Answer 5

The liquid formed

Question 6

What is meant by saturated solution

Answer 6

A solution into which no more solute can be dissolved

Question 7

What is meant by the term solubility in the units g per 100g of solvent

Answer 7

Solubility is defined by the maximum amount of solute that is dissolved in 100g of solvent. The mass depends on the temperature

Question 8

Solubility practical

Answer 8

Set water bath to a specific temperature
Use water from water bath and add into beaker
Add solid into beaker and measure time taken for solid to dissolve

As temperature increases the time taken for solid to dissolve will decrease as kinetic energy increases which will overcome the intermolecular forces between the particles

Question 9

Describe simple distillation

Answer 9

• used to separate a liquid from a solution

Method
- salt water is boiled
- water vapour condenses back into a liquid when passed through the condenser
- salt is left behind in the plasm flask

Question 10

Describe crystallisation

Answer 10

• used to get a salt which contains water of crystallisation from a salt solution

Method
- heat solution in evaporating basin to evaporate some of the water
- Do this until crystals form on a glass rod
- Leave to cool and crystallise
- Filter to remove crystals
- dry be leaving in a warm area

Question 11

Rf value =

Answer 11

Distance of dye from baseline/distance of solvent front

Question 12

Why do we use a lid when doing paper chromatography ?

Answer 12

So no solvent can evaporate from the surface of the paper

Question 13

Mass and charge of a proton

Answer 13

Mass - 1
Charge - +1

Question 14

Mass and charge of neutron

Answer 14

Mass - 1
Charge - 0

Question 15

Mass and charge of electron

Answer 15

Mass - 1/1836
Charge - -1

Question 16

What is the atomic number

Answer 16

Number of protons in an atom

Question 17

What is the mass number

Answer 17

Number of protons and neutrons in an atom

Question 18

What is the relative atomic mass

Answer 18

Average mass of an atom compared to 1/12 the mass of a carbon-12 atom

Question 19

How to calculate relative atomic mass of an element from isotopic abundances

Answer 19

1. Multiply the mass of each isotope by its relative abundance
2. Add those together
3. Divide by the sum of all the relative abundances ( mostly will = 100 )