C4) Chemical Calculations Flashcards
What is the Avogadro constant in standard form?
6.02 * 10**23/mol.
What is the equation for calculating moles from masses?
Number of moles = mass (g) ÷ A[r] or mass (g) ÷ M[r].
What is a limiting reactant?
The reactant that gets used up first in a reaction.
What is the mass of the product that a chemical reaction produces called?
Its yield.
What is the formula for calculating percentage yield?
Percentage yield = (actual mass or product produced ÷ maximum theoretical mass of product possible) * 100%.
What factors affect percentage yield?
The reaction may be reversible.
Some reactants may react to give unexpected or unwanted products in alternate reaction.
Some products may be lost in handling or left in apparatus.
Reactants may not be pure.
Some of desired product may be lost during separation from reaction mixture.
Why would reaction being reversible affect percentage yield?
Products formed react to re-form reactants again.
What is the equation used to work out the atom economy of a particular reaction?
Percentage atom economy = (relative formula mass of desired product from reaction ÷ sum of relative formula masses of reactants from equation) * 100%.
What is the equation for calculating the concentration of a solution?
Concentration (g/dm3) = ( amount of solute ÷ volume of solution (cm3) ).
What is titration?
Technique for finding out how much acid needed to completely react with an alkali.
What is the end point of the reaction (in titration)?
When the end point reached by using acid/base indicator.
