Chemical Analysis Flashcards
What is a pure substance
A pure substance consists of a single element
What is a mixture
A mixture consists of 2 or more elements or compounds that are physically mixed together not chemically combined
How can you distinguish a pure substance
Pure substances melt and boil at specific and sharp temperatures e.g. pure water has a boiling point of 100°C and a melting point of 0°C whereas mixtures have a range of melting and boiling points as they consist of different substances that tend to lower the melting point and broaden the melting point range
What is a formulation
A mixture that has been designed for a specific purpose to deliver a commercial product, they are made by following an exact recipe so the final product has required properties
Why are formulations important in the pharmaceutical industry
By changing the formulation of a particular medicine chemists can make sure it delivers the drug to the correct part of the body at the right concentration , so that its safe to consume and has an adequately long shelf life
What are 3 examples of formulations
Paint, cleaning agents and fuels
What is chromatography used for
Chromatography is used to separate substances and provide information to help identify them
Why does chromatography work
The components have different solubilities in a given solvent and different adhesion to the supporting medium- usually paper
What is the method for chromatography
A pencil line is drawn on the chromatography paper and spots of the sample are placed on it, the paper is then lowered into the solvent container, making sure the pencil line sits above the level of the solvent so the samples don’t wash into the solvent container. The solvent travels up the paper, taking some of the coloured substances with it, as the different substances have different solubilities so will travel at different rates causing the substances to spread apart those substances with higher solubility will travel further than the others
What is the mobile phase
The solvent
What is the stationary phase
The chromatography paper
What will the chromatogram of a pure and impure substance look like
A pure substance will produce only one spot whereas an impure substance will produce a chromatogram with multiple spots
What is an Rf value
the ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent
What does Rf stand for
Retention facor
What is the equation for Rf
Distance moved by the substance / distance moved by the solvent
(it will never be higher than one and is written in 2 decimal places)
What is the test for hydrogen
Squeaky pop test
What is the squeaky pop test
You hold a burning splint at the open end of a test tube of gas, if the gas is hydrogen it burns with a loud ‘squeaky pop’ which is a result of the rapid combustion of hydrogen with oxygen to produce oxygen be sure to not insert the splint right into the tube just at the mouth as the gas needs air to burn
What is the test for oxygen
Glowing splint test
What is the glowing splint test
You place a glowing splint inside a test tube of gas if the gas is oxygen the splint will relight
What is the test for carbon dioxide
Limewater test
What is the limewater test
The test for carbon dioxide involves bubbling the gas through an aqueous solution of calcium hydroxide (limewater) if that gas is carbon dioxide, the limewater turns milky or cloudy
What is the test for chlorine
The litmus paper test
What is the litmus paper test
If chlorine gas is present the damp blue litmus paper will be bleached white when dipped in the gas, it may briefly turn red before bleaching as acids are produced when chlorine come into contact with water. Chlorine should always be handled in a fume cupboard due to its toxicity
