topic 4 chemical calcualtions Flashcards
what is the law of conservation of mass?
matter cannot be created or destroyed, so no atoms are created or destroyed during a chemical reaction. the total mass of the products is equal to the total mass of the reactants
if the mass appears to have changed after a chemical reaction, what has happened?
either one of the reactants was a gas that was pulled from the atmosphere (mass is heavier), or one of the products was a gas that escaped into the atmosphere (mass is lighter)
what is the symbol for reletive atomic mass?
Ar
what is reletive formula mass
the sum of all the atomic masses of the atoms in a formula of a substance
what is uncertainty
the interval within which the true value can be expected to lie
what is a mole?
the amount of substance in the reletive atomic or formula mass of a substance in grams
what is the formula for moles?
mol = 6.02 x 10²³ (the avogadro constant) x Ar or Mr
what is a balanced equation
an equation that shows the number of moles that react, eg Ca + 2HCl -> CaCl + H
² ²
what is a limiting reactant?
the reactant that gets used up first in a chemical reaction and limits the amount of product formed
what is an excess reactant?
the reactant that is not completely used up in a chemical reaction. there is some reactant left over at the end
what is concentration?
a measure of the number of particles of a chemical in a volume, can be measured in g/dm³
what is a decimetre³ (dm²)?
a measurement of volume
