Quantative Chemstry Flashcards
1 mole
- mol
- Avagadro number of particles in a substance
Avagadros number
- one mol
- 6.02x 10^23 atoms
Mol
Mass/mr
Atomic number
Number of protons or electrons
Mass number
Number of protons and neutrons
Isotypes
- Atoms of the same element
- same atomic number- same number of protons
- diff no. Neutrons (diff mass number)
How to calculate mass of product/reactant of reaction
- balanced equation
- find ratio between products/reactants
- find mr of chemicals interested in
- calculate no. Mole from chemical given mass
- use ratio to calculate no. Mol in other chemicals
- calculate mas from mol
How to balance equations from given masses
- calculate mol from given mass
- divide : no mol of each substance/smallest no of mol in reaction
- make ratio from this
- implement into balanced symbol equation
Limiting reactant
- in a chemical reaction w/ two reactants, common to use an excss of one of the reactants to ensure all of the other is used
- reactant that is completely used up is the. Limiting reactant
- limits amount of product that can be made
- amount of product fromed is directly proportional to amount of limiting reactant
Relative formula mass (definition)
Sum of relative atomic masses of the atoms in the numbers shown in the formula
-mr
Relative atomic mass
- average mass of all diff isotypes of an element
- ar
- (ar x abundance)/number of isotypes(100)
Atom “ economy
Mr of desired product x 100 / mr of all reactants
Percentage purity
Mass of pure product x 100/ actual mass
Concentration
- amount of mol of solute in a given volume of solution
- mol/dm3
Volume of gas - at 20C and 1atm
24 x mol
How to find the conc of other solution
- find mol of other solution:
- mol=conc x vol
- use ratio to find mol of other solution
Standard solution
Has an accurately known conc
Percentage yield
Actual mass of product x 100 / max mass of product
0% percentage yield
No product made
Why is percentage yield not 100%
- reaction may not go to completion because its REVERSABLE
- some of product may be lost when its SEPERATED from the reaction mixture
- may react in a diff way to expected reaction
- evaporation
- not all reactants react to make products
How to find percentage yield
- find mr
- work out mass theoretical mass
- Mr x n of molecules eg. 2Cl = x2
- divide this number by no. Mr of reactants
- times result by theoretical mass eg. 50g = x50
- use formula
Percentage by mass
Mr of element x 100 /mr of compound
Converting from mol/dm3 -> g/dm3
Conc (mol/dm3) x mr
Molar vol of gases
Equal amounts of moles of gases occupy same volme under same conditions of temp and pressure
Mol of gas (equation)
Vol(dm3)/24dm3. = vol(cm3)/24 000cm3
How to calculate mass of gas
- calculate no. Of mol
- find molar ratio
- find mol of gas
- find mass =mr x mol =g
Atom economy (utilisation)
- measure of amount of starting materials that end u as desirable product
- used for sustainable development
- used for economic reasons -use reactions w/ high atom economy
Why is a particular reaction pathway used?
- atom economy
- yield
- rate of reaction
- equilibrium position (how stable/easy to push one way)
- usefulness of by-product
- cost of materials, heat, pressure
- safety (high pressure/toxicity)
- sustainability (crude oil)
- availability
- waste disposal
- pollution
- energy requirements
