C4: Chemical Calculations Flashcards
What is a limiting reactant in a chemical reaction?
The chemical/element that is completely used up during the reaction
Why can the percentage yield never be above 100%?
Because if the percentage yield was above 100% then there would be more product obtained than the maximum mass created.
How do you figure out relative atomic mass of a substance/compound?
You multiply all the elements atomic mass by how many times they appear.
For example in H2O
H = 1 x 2 = 2
O = 16 x 1 = 16 2 + 16 = 18
What is atom economy?
A measure of how efficient a chemical reaction is
How do you calculate atom economy?
It is calculated by dividing the relative atomic mass of the desired product, by the total relative atomic mass of the reactants and multiplying by 100.
For example,
CO + H2O = CO2 + H2 Work out the atom economy of H2
28 + 18 = 44 + 2
2/46 x 100 = 4.35%
H2 + O2 -> H2O
Balance this equation
2H2 + O2 -> 2H2O
How do you convert between Mol/dm^3 and G/dm^3?
Multiply the mol/dm^3 by the Mr of the substance
If you have 1 mole of any gas, how much dm^3 will it fill?
24dm^3
What is avogrados number?
6.022 x 10^23
What is a mole?
The amount of substance that contains 6.022 x 10^23 particles of that type of substance
How do you calulate % yield?
Actual mass obtained
divided by
The theoretical mass too be obtained
What is the equation that links mass, number of moles and relative formula mass mass?
Number of moles = Mass / Relative Formula Mass
What is the calculation triangle linking mass, volume and concentration?
Mass on the top
Concentration in the bottom left
Volume in the bottom right
How do you convert from cm^3 to dm^3?
You divide the substance in cm^3 by 1000 to convert it into dm^3
E.g 2000cm^3 / 1000 = 2dm^3
What is always formed when a metal reacts with an acid?
Salt + Water
