c4. Chemical calculations Flashcards
What is the law of conservation of maths?
A law that states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of reactants
What is relative formula mass?
It is the sum of relative atomic masses of the atoms in molecules
Why do some reactions appear to increase in mass?
When substances react with gases in the air such as oxygen, the mass will increase
Why do some reactions appear to decrease in mass?
When a gas is a product in a chemical reaction and it is released into the atmosphere
How do you calculate uncertainty?
Calculate the range in the results and divide by two
What are chemical amounts measured in?
Moles
What are the units for moles?
Mol
What is the value of avogadro constant?
6.02×10*23
what is a limiting reagent?
it is the reactant that is completely used up that limits of the amount of products
What are the units for concentration?
Mass per given volume
Why is it not always possible to obtain the calculate amount of product?
The reaction may not go to completion because it’s reversible some of the product may be lost when it is separated from the reaction mixture or some of the reactants may react in ways different to the expected reaction
What is yield?
The amount of product obtained in a reaction
How can yield be calculated?
% mass = ( mass of product / theoretical mass ) x 100
What is atom economy?
A measure of the amount of starting materials that end up as useful products
Why is it important to use reactions with high atom economy?
For sustainable development and for economic reasons
How can atom economy be calculated?
Atom economy = (RMF of desired product / RFM of all reactants) x 100
What is the unit for concentration?
mol/dm*3
