Chemistry topic 8 Flashcards
(14 cards)
What does purity mean?
Usually purity means nothing has been added to it, so it’s in its natural state such as milk.
In chemistry, a pure substance is something which only contains one compound or element throughout, not mixed with anything else.
How can you work out how pure a substance is?
Are chemically pure substance, will melt or boil at a specific temperature. You can test its Purity by measuring It’s melting and boiling points, then comparing it with the melting or boiling points of the pure substance. The closer, the measured value is to the actual melting or boiling point, the purer of the sample. Impurities will lower the melting point and increase the melting range. They will also increase the boiling point, and may result in boiling at a range of temperatures.
What is a formulation?
Useful mixtures with precise purposes, made by following a formula. Each component is present in a measured quantity and contributes to the properties of the formulation, so it meets its required function. They are really important in the pharmaceutical industry, e.g. altering the formulation of a pill, chemist, to make sure it delivers the drug to the correct part of the body at the right concentration that it’s consumable and has a long shelf life.
In every day, life formulations can be found in cleaning products, fuels, cosmetics etc.
Products have information on the packaging such as the ratio or percentage of each component, telling you the products formulation. (Different formulations for different uses).
What formulations are paints composed of?
Pigment (colour)
Solvent (dissolve other components, alter viscosity)
Binder (resin, holds pigment in place)
Additives (change, physical and chemical properties of the paint).
What is chromatography?
An analytical method used to separate the substances in a mixture. You can then use it to identify the substances, there are different types of chromatography, but they all have two phases.
What are the two phases in chromatography?
Mobile phase - where the molecules can move. This is always a liquid or a gas.
Stationary phase - where the molecules can’t move. This can be a solid or a really thick liquid.
What happens during chromatography?
Substances in the sample constantly move between a mobile and stationary phase and an equilibrium is formed between the two.
Mobile phase moves through the stationary phase and anything dissolved in the mobile phase moves with it. How quickly a chemical moves depends on how it’s distributed between the two phases.
The chemicals that spend more time in the mobile phase will move further through the stationary phase.
The components in a mixture, normally separate through the stationary phase, as long as the components spend different amounts of time in the mobile. Number of sports changes in different solvents, as the distribution of chemical changes depending on solvent. (Pure substances, only other form one spot in any solvent.)
In terms of phases, what happens during paper chromatography?
The stationary phase is the chromatography paper, and the mobile phase is the solvent.
Amount of time spent in each phase, depends on the solubility and attraction to paper.
Molecules with high solubility and less attraction to paper will spend more time in the mobile phase (carried far up the paper).
What is an RF value?
The ratio between the distance, travelled by the dissolved substance in the distance, travelled by the solvent in chromatography.
How do you calculate the RF value?
Distance travelled by substance divided by the distance travelled by solvent
What is the test for chlorine gas?
Chlorine bleach is damp, litmus paper, turn in at White as it’s acidic.
What is the test for oxygen gas?
If you put a glowing splint inside a test tube containing oxygen, the oxygen will relight the glowing splint
What is the test for carbon dioxide?
Bubbling carbon dioxide through an aqua solution of calcium hydroxide (limewater), causes the solution to turn cloudy
What is the test for hydrogen?
If you hold a lit splint into the test tube containing hydrogen, you’ll get a squeaky pop.
