C17 - CHEMICAL ANALYSIS

Chemistry topic 17 (chemical analysis)

What is a pure substance?

A substance that contains a single element or compound

What is an impure substance?

a substance that contains more than one type of element of compound in a mixture

What is chromatography?

A method used to separate different components in a mixture

What is the R1 value in chromatography?

A ratio of how far up the paper a certain spot moves compared to how far the solvent has moved

How do you calculate the R1 value in chromatography?

Distance moved by substance/distance moved by solvent

In chromatography, what does the distance the substance moves up the paper tell you about it?

If it travels far it is very soluble and vice versa

What is a formulation?

A mixture that is designed for a specific purpose

Give two examples of formulations?

Fuels and paints

What is the test for hydrogen?

Lit splint gives a squeaky pop if hydrogen is present

What is the test for oxygen?

Relights a glowing splint if oxygen is present

What is the test for carbon dioxide?

Turns limewater cloudy when bubbled through it

What is the test for chlorine?

Bleaches damp litmus paper

What is a cation?

A positively charged ion

What is a anion?

A negatively charged ion

What compound is used to test for positive ions?

Sodium Hydroxide

What result comes from mixing aluminium ions with sodium hydroxide?

On slow addition of excess sodium hydroxide solution, white precipitate forms that eventually dissolves again with excess sodium hydroxide

What result comes from mixing calcium ions with sodium hydroxide?

On addition of excess sodium hydroxide solution, white precipitate forms that does not dissolve

What result comes from mixing magnesium ions with sodium hydroxide?

On addition of excess sodium hydroxide solution, white precipitate forms that does not dissolve

What result comes from mixing Copper (2) ions with sodium hydroxide?

Forms a blue precipitate

What result comes from mixing Iron (2) ions with sodium hydroxide

Forms a green precipitate

What result comes from mixing Iron (3) ions with sodium hydroxide

Forms a brown precipitate

What is the test and result for finding out if carbonate is an anion?

Add dilute acid. A positive result will cause carbon dioxide to be formed which can be tested for with limewater

What is the test and result for finding out if chloride is an anion?

Add silver nitrate solution in the presence of nitric acid. A positive result will cause white precipitate to be formed

What is the test and result for finding out if bromide is an anion?

Add silver nitrate solution in the presence of nitric acid. A positive result will cause cream precipitate to be formed

What is the test and result for finding out if iodide is an anion?

Add silver nitrate solution in the presence of nitric acid. A positive result will cause yellow precipitate to be formed

What is the test and result for finding out if sulfate is an anion?

Add barium chloride solution in the presence of nitric acid. A positive result will cause white precipitate to be formed

Using the flame test, what flame colour will occur with lithium?

Crimson

Using the flame test, what flame colour will occur with sodium?

Yellow

Using the flame test, what flame colour will occur with potassium?

Lilac

Using the flame test, what flame colour will occur with calcium?

Orange/Red

Using the flame test, what flame colour will occur with copper?

Green

What does instrumental analysis involve?

Using complex scientific equipment to test substances

Give an example of an instrumental analysis method?

Flame Emission Spectroscopy

What is the method for Flame Emission Spectroscopy?

The sample solution is put into a flame and the light given off is passed through a spectroscope. Instead of a human observing a colour, the instrument tells you exactly which wavelength of light is being given off as a line spectrum.

What is a more accurate method instead of "The Flame Test"

Flame Emission Spectroscopy

Name the three substances that dissolve in water?

Ionic Compounds, strong acids, strong alkalines

What is Nitric acid's molecular formula?

HNO3

When testing to see which substances are calcium and magensium, how do you didtinguish the two (as they both from a white precipitate that does not dissolve)?

The Flame Test