C2.3 Isotopes, chromotography and how much? Flashcards
define chromatography
Using water to separate inks or substances
What are the benefits of chromatography? [2]
- Easy to use
- Not expensive
What are the disadvantages of chromatography? [2]
- Hard to tell what is there
- Not as accurate
Define instrumental methods
Using equipment to separate substances
What are the benefits of using instrumental methods? [3]
- Very accurate
- Quicker than older methods
- Analyses small samples
What are the disadvantages of using instrumental methods? [2]
- Expensive
- You need specialist training
What is the equation for working out yield?
Percentage yield = actual yield/predicted yield x 100
What is an isotope?
An element that has different form but with a higher mass number
Why can isotopes become radioactive?
Because the nucleus becomes unstable
What happens to the chemical properties of an isotope?
Nothing
What happens to the physical properties of an isotope? [2]
- Different density
- Might be radioactive
How do you find formula mass?
The formula mass of a molecule is the sum of the atomic weights of the atoms
Define molar mass
The relative formula mass in grams
unit = g/mol
What is a mole?
Relative molecular mass of a compound
How do you find the empirical formula?
1) Find the masses of each element by adding its protons and neutrons together
2) Look up each element’s relative atomic mass
3) divide the masses by the relative atomic mass
4) Find the ratio by dividing each by the smallest number
