Topic 8- Chemical Analysis Flashcards
Define a pure substance
A pure substance is one that is made up of just one substance. That substance can be an element or a compound
They melt and boil at specific temperatures
Define a mixture
A mixture contains more than one type of substance, not chemically combines and not in a fixed composition.
These substances can be elements or compounds, or a combination
They will melt or boil over a range of temperatures
Define a formulation
A mixture that has been designed as a useful product
They are made by mixing the components in carefully measured quantities to ensure that the product has the required properties
E.g: medicinal drugs, fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods
What is paint made up of?
A pigment to provide colour
A binder to help the paint attach itself to an object and to form a protective film when dry
A solvent, to help the pigment and binder spread well during painting by thinning them out
Define an alloy
It is a mixture made up of two or more metals
Explain how an alloy behaves differently to pure gold so that it is suitable for jewellery
The layers are distorted due to the varying sizes of atoms meaning they can’t slide over each other. This means they are harder than pure metals, making them suitable for jewellery
Describe paper chromatography
Make sure that the chromatography paper can fit into the boiling tube
Use a pencil to draw a horizontal base line, 1cm from the bottom of the paper
Use a pencil to draw a cross on the centre of the base line
Use a paint brush of capillary tube to add some or the food colouring onto the cross and allow to dry
Fold the top edge of the chromatography paper over a wooden splint and keep in place with a paper clip
Add 0.5cm not fin..
How is Rf calculated?
Distance moved by the spot/distance moved by solvent
Test for hydrogen
Use a burning splint held at the open end of a test tube of the gas
Creates a ‘squeaky pop’ sound (hydrogen burns rapidly)
Test for oxygen
Uses a glowing splint inserted into a test tube of the gas
Splint relights in oxygen
Test for carbon dioxide
Bubble the gas through the limewater (calcium hydroxide (aq))
It will turn milky
Test for chlorine
Use damp litmus paper
When damp litmus paper is put into chlorine gas, the litmus paper is bleached and turns white
Flame test for lithium
Crimson
Flame test for sodium
Yellow
Flame test for potassium
Lilac
Flame test for calcium
Orange-Red
Flame test for copper
Green
Aluminium, calcium and magnesium ions form what colour precipitate with NaOH
White precipitate
Which of the metal hydroxides dissolves when excess NaOH is added
Aluminium
What colour precipitate does copper (II) produce?
Blue
What colour precipitate does iron (II) produce?
Green
What colour precipitate does iron (III) create?
Brown
Describe the test for carbonate anions
Carbonates react with dilute acids to create carbon dioxide
The gas can be bubbled through limewater, if the limewater goes cloudy, the gas is CO2
Describe tests for halides
First add dilute nitric acid, followed by silver nitrate solution
