Quantitative chemistry Flashcards
How do you find percentage mass of an element in a compound?
((Ar x number of atoms in that element) / Mr of the compound) x 100
What is Avogadro’s constant?
6.02 x 10²³
What is conservation of mass?
During a chemical reaction, no atoms are created or destroyed
In what situation would the mass of a reaction change?
If there has been a gas produced which had then escaped or if a reactant was taken from the air and was not measured
What is the volume of any gas at 20C?
24dm³`
How do you find volume of gas in dm³?
(mass of gas / mr of gas) x 24
How do you find concentration in g/dm³?
Mass (g) / volume (dm³)
How do you find concentration in mol/dm³?
Number of moles / volume (dm³)
How do you convert mol/dm³ to g/dm³?
Use the equation mass = moles x Mr
What is the formula for atom economy?
Atom economy = (relative formula mass of desired products / relative formula mass of all reactants) x 100
What is atom economy?
The percentage of reactants that form useful products
What does 1005 atom economy mean?
That all the reactants have been turned into useful products
Finish this sentence: The higher the atom economy
The more environmentally friendly the process
Why are low atom economy reactions less preferred?
They create more waste which has to be disposed of, use up resources very quickly, aren’t profitable and waste rarer resources
How can low atom economy reactions be made more helpful?
By finding other uses for the waste, such as a useful by-product
What type of reactions have the highest atom economy?
The ones with only one product, this means that atom economy is always 100%
What is the formula for percentage yield?
Percentage yield = (mass of product actually made / maximum theoretical mass of product) x 100
What is yield?
The amount of product you get
Why should industrial processes have a high yield?
It would mean reduced waste and reduced costs
Why will you never get a 100% yield?
Because products or reactants always get lost along the way
What things can reduce yield?
In reversible reactions, products turn back, there might be side reactions from impurities or gases in the air and product can be lost when it is separated from the reaction mixture
