Topic 3 - Quantitative Chemistry Flashcards
What is the relative formula mass of a substance?
All of the atomic masses added together
What is the law of conservation of mass?
No atoms can be lost or gained in a chemical reaction
How can we use the law of conservation of mass to work out the amount of reactant used when given the masses of the products?
Add the masses of the products together
Why might there be a change in mass in a reaction?
It took place in a non-enclosed system
How do you work out the uncertainty of a set of results?
The uncertainty is half the range. e.g. find the mean of the results (24), take the smallest from the biggest (25-23 = 2), divide this by two (1). This would be written as - 24 +/- 1
What is the Avogadro constant?
The number of particles in one mole of a substance is 6.02x10^23
Calculate the number of oxygen atoms in 0.5mol of O2
- 02x10^23 x 0.5 x 2
- 01x10^23 x 2
- 02x10^23
How do you work out the mass in regards to the mole?
mass = relative formula mass x mol
How do you work out the equation for a reaction when given the masses?
Calculate the amount of moles in each substance. Divide both by the smaller amount
What is the limiting reactant?
The reactant that is all used up
How do you work out the concentration?
Concentration in mol/dm^3 = amount of substance (mol)/ volume (dm^3)
How do you convert mol/dm3 to g/dm3 and vice versa
Multiply (to g/dm3) by relative formula mass. Divide by rfm for opposite.
How do you work out the atom economy?
(total Mr of desired product/total Mr of all reactants) x 100
How do you work out percentage yield?
(mass of product made/maximum theoretical mass of product) x 100
What is the theoretical yield?
The maximum amount of product that can be made
