Topic 3: Qunatitative Chemistry (Paper 1) Flashcards
What does the law of conservation of mass state?
The law of conservation of mass states that no atoms are lost or made during a chemical reaction
mass of the products = mass of the reactants
What is Ar
The relative atomic mass of an element is the average mass of the isotopes weighted to take into account the abundance of each isotope
Ar = (%1 x mass 1) + (%2 x mass 2)
What is Mr?
The relative formula mass of a compound is the sum of the relatice atomic masses of the atoms in the numbers shown in the formula.
What is the equation for moles?
number of moles (mol) = mass (g) ÷ Mr
What number is Avogadro’s constant?
1 mol = 6.02 x 10^23 atoms
What is a limiting reactant?
What is an excess reactant?
The limiting reactant is the one that is fully used up and runs out first.
An excess reactant is the reactant that dosen’t get fully used up.
What is concentration?
What is the two equations for concentration?
Concentration is the mass of a solute in a given volume.
concentration (g/dm3) = mass (g) ÷ volume (dm3)
concentration (mol/dm3) = moles (mol) ÷ volume (dm3)
What happens to the concentration if we increase the mass but keep the volume the same?
What happens if we increase the volume of solution but keep the mass of the solute the same?
If we increase the mass of the solute and keep the volume the same, then we also increase the concentration
However, if we increase the volume but keep the mass the same, the concentration decreases.
What is it not always possible to achieve a 100% percentage yeild in a chemical reaction?
- Some of the produce may be lost when it is separated from the reaction mixture
- Some of the reactants may react in different ways to the expected reaction
- reversible reactions may not go to completion
What is the equation for percentage yeild?
% yeild = (actual ÷ theoretical yeild) x 100
What is atom economy?
The atom economy (Atom utilisation) is a measure of the amount of starting materials that end up as useful products.
Why is a high atom economy desirable?
- Sustainable development (not wasting resources)
- Economic reasons (minimise production of unwanted products = save movey)
What is the equation for atom economy?
AE = (Mr of desired products ÷ sum of Mr of all reactants (big numbers count)) x 100
How can money not be wasted?
When reactions produce unwanted side-products, money is wasted. Chemists can try to find a use for these side-products, e.g in other reactions. This way, money isn’t wasted.
What volume does 1 mol of any gas occupy at room temperature and pressure?
at room temperature and pressure (rtp) 1 mol of any gas occupies 24dm3
