Quantitative chemistry Flashcards
How do you calculate percentage yield?
actual mass/ theoretical mass X 100
What does being in excess mean?
Some of the reactant will be left over after the reaction
How can results be made more precise for mass?
Use a balance to more decimal places
Why is it important to have a high percentage yield?
Reduces waste and costs (economic and sustainable reasons)
Why is it important to have a high atom economy?
- More profitable (economic reasons)
- Reduces waste
- More sustainable (environmental reasons)
Why may maximum yield not be achieved?
- Some product lost
- Reversible reaction: not gone to completion/ not all atoms reacted
- Unexpected side reactions forming unexpected products
What is atom economy?
A measure of the amount of starting materials that end up as useful products
How can we measure uncertainty?
Range/2 . This can then be shown as the mean +- range/2
State the law of conservation of mass
No atoms are lost or made during a chemical reaction so mass of products equals mass of reactants
What is the Avogadro constant?
The number of atoms, molecules or ions in a mole of a given substance (6.02x10^23 is 1 mole of any given substance)
How to plan investigation for thermal decomposition of a metal carbonate to see a change in mass?
- weigh test tube
- add metal carbonate
- weigh test tube and metal carbonate
- heat
- allow to cool
- repeat until no change in mass
- determine mass of metal carbonate used
- determine mass of carbon dioxide produced
- repeat with different metal carbonate(s)
